Control Tools

• Diagnostics availability

• Commercial diagnostic kits available worldwide

  For Salmonella detection, a list of patent kits even validated against ISO 6579:1, is available. These diagnostic kits, generally based on molecular methods, are faster and easier to perform compared to traditional microbiological isolation methods. Anyway, the isolation of Salmonella remains an essential step for carrying out additional investigations (e.g. serotyping and further typing of Salmonella isolates).

  GAPS

  The need for validation of diagnostic tests and kits for Salmonella detection: there may be interest in new approaches, covering also alternative matrices, e.g., air, to explore other transmission routes (Ruiz-Llacsahuanga et al., 2024). The need for diagnostic tests and kits for Salmonella typing: Salmonella serotyping remains an analysis primarily performed by reference laboratories. Nevertheless, identifying a Salmonella serovar is a crucial point in the epidemiological context of the disease. The availability of rapid and user-friendly diagnostic kits for the identification of Salmonella serovars would be highly beneficial.

  Full details of the gap analyses matrices for Salmonellosis can be found on the website and downloaded here.

• Diagnostic kits validated by International, European or National Standards

  A molecular serotyping test (Check&Trace Salmonella) targeting the main Salmonella serovars including Typhimurium and Enteritidis has been validated and certified by WOAH. An ELISA assay for the detection of IgG anti-Salmonella Abortusovis in sheep serum samples has been validated and certified by WOAH -https://www.woah.org/en/what-we-offer/veterinary-products/diagnostic-kits/the-register-of-diagnostic-kits/ There are numerous commercial diagnostic kits for Salmonella detection in foodstuffs and diagnostic samples collected at primary production level and part of these methods are also validated according to the EN ISO 16140 standards.

  GAPS

  In a diagnostic context, it may be useful to combine a rapid molecular screening method with, in the case of a positive detection, a microbiological method to isolate Salmonella strains for further characterization. This approach allows to speed up the identification of negative groups especially in the area with a low Salmonella prevalence. In general, diagnostic programmes involving two tests, where the first would have a high sensitivity and the second would have a high specificity, would create the best set-up for detecting truly positive flocks/farms.

• Diagnostic method(s) described by International, European or National standards

  The following ISO standards are available for Salmonella diagnosis: ISO 6579 – Microbiology of the food chain – horizontal method for the detection, enumeration and serotyping of Salmonella Part 1 Detection of Salmonella spp. Part 2 Enumeration by a miniaturized most probable technique Part 3 Guidance for serotyping Salmonella spp. Part 4 Identification of monophasic Salmonella Typhimurium (1,4, [5], 12:-) by polymerase chain reaction (PCR) Numerous diagnostic methods, mainly based on traditional microbiology (using different cultural media), molecular techniques (mainly PCR based) and immunologic tests are available for Salmonella detection in different matrices and in diagnostic samples.

  GAPS

  A rapid and cost effective method for the quantification of Salmonella from different matrices is missing. Phage typing characterisation of certain serotypes of Salmonella is being mostly phased out as reference phases are no longer produced. An alternative method to associate Salmonella strains to specific hosts still needs to be fully developed. In general, Salmonella typing, which is essential in the context of epidemiological investigations, and outbreaks assessment, requires methods that are affordable and user-friendly to be used by most laboratories.

• Commercial potential for diagnostic kits worldwide

  There is commercial potential for validated tests in Europe.

  GAPS

  Rapid, reliable and affordable kits for Salmonella serotyping validated against the reference serotyping method (ISO 6579:3) would be appreciated. Simple-to-use kits for subtyping Salmonella isolates, would be beneficial to better support surveillance and epidemiological studies.

• DIVA tests required and/or available

  Salmonella vaccination is not aimed at eradicating the disease or at economically controlling the pathogen. Vaccination is used in some EU countries and for certain animal species (mainly poultry, more rarely in pigs and cattle animals), as a tool for Salmonella control, alongside other measures such as biosecurity, cleaning and disinfection, and pest control. In other countries, however, vaccination is not permitted. In any case, where vaccines are used, DIVA tests (based on phenotypic and genotypic methods) are available.

  GAPS

  Currently, in the countries where vaccination is used as a control strategy for Salmonella, there are no gaps in the differentiation between vaccine and field strains using the available diagnostic methods.

• Opportunities for new developments

  Opportunities for rapid diagnostic detection at the farm level by authorities or official vets to reduce diagnostic time and spread of infected eggs into the market.

• Vaccines availability

• Commercial vaccines availability (globally)

  Inactivated and live Salmonella vaccines are available mainly for S. Enteritidis and Typhimurium in mono or bivalent preparations. Inactivated vaccines include bacterins and autologous vaccines. Oral attenuated live vaccines include auxotrophic and metabolic drift mutants used to prevent Salmonella infections in poultry. In general, it is demonstrated that live Salmonella vaccines are more effective against both intestinal and systemic infection than inactivated vaccine preparations, because the live vaccines stimulate both the cellular and humoral arms of the immune system. Homologous immunity between strains of the same serovar is considerably stronger than between strains of different serovars. Vaccination schemes using combinations of live and inactivated Salmonella vaccines have been shown to be effective. The EU, following advice from EFSA, recommends the use of vaccination as part of a comprehensive approach to Salmonella control, although adoption varies across different EU countries according to their epidemiological situation. The following assessment examines the current situation in three countries situated in the northern, western, and southern regions of the EU. In the North, vaccines against Salmonella are not used, neither in pigs nor in poultry. The prevailing perception is that no vaccine offers full protection. As a result, biosecurity is considered the most important strategy for preventing infection, and substantial investments are made to keep Salmonella out. In the West and South EU, vaccination is routinely used, particularly to control S. Enteritidis and S. Typhimurium in poultry flocks (breeders and laying hens). Vaccination is defined as a control measure within the framework of National Control Programmes for poultry flocks in these countries. Data collected have demonstrated a positive correlation between vaccination and Salmonella prevalence in poultry and the number of ascribed human cases (Lane et al., 2014). For pigs in the West, vaccination is used in farms where clinical salmonellosis is observed. Several trials have been conducted in pigs in the UK using a live attenuated vaccine (Smith et al., 2018) and it seems that there is a direct clinical advantage in using the vaccine. However, if the within-herd prevalence of Salmonella ​is high (e.g. ≥ 20%) the efficacy of the vaccine is reduced as vaccination cannot overcome high levels of environmental contamination​. A summary of the commercial vaccines against salmonellosis in different animal models (chicken, swine, sheep/cattle) has been carried out by Siddique et al. (2024).

  GAPS

  Multi -serovar/serogroup protection - Work to define efficacy of different serovar combinations programmes - In some geographic areas, serovars other than S. Enteritidis and S. Typhimurium are becoming prevalent in different species — for example, Salmonella Infantis in broilers. Vaccines for serovars other than S. Enteritidis and S. Typhimurium do exist, and others are currently under development, although the availability remains limited. Candidate vaccines should be developed targeting S. Infantis as well as other emergent serovars (e.g. S. Kentucky). Moreover, the efficacy of cross-protection provided by authorized vaccines for other serovars should be investigated. Use of attenuated and safe strains during egg production. In countries where vaccination is used, there is a need to expand the availability of live vaccines — especially against S. Enteritidis and S. Typhimurium — that are authorized for use during the laying phase. Effectiveness of vaccination during later stages of lay. As more and more producers tend to keep laying hens in production for longer than observed before (i.e. 90-100 weeks of age), it is unclear whether the vaccinal protection of available products extends to this duration.

• Marker vaccines available worldwide

  Live vaccines can be used safely provided that detection methods are able to differentiate the vaccine strain from other wild-type strains. Some live vaccines (metabolic drift mutant strains) may be differentiated by using markers such as resistance to antimicrobials. Molecular methods for the differentiation of vaccine strains from field strains are available. In areas where S. Gallinarum is present, parenteral administration of inactivated Salmonella vaccines induces a stronger antibody response, which may interfere with serological testing.

  GAPS

  Development and availability of marker vaccines. Availability of attenuated live for those serovars causing clinical infections especially in species different from poultry (e.g. pigs and bovine) In some critical situations, and in certain EU countries, for example, in the case of widespread clinical infections caused by invasive serovars such as S. Dublin in cattle and S. Choleraesuis in pigs, commercial live vaccines are not always available. In these cases, in some geographic areas autogenous vaccines are used. The constant availability of vaccines to control such serovars, in populations severely affected by these infections, could be highly beneficial.

• Effectiveness of vaccines / Main shortcomings of current vaccines

  Salmonella vaccination programmes have been considered a successful measure for reducing Salmonella prevalence in several EU countries, particularly in relation to control programmes targeting poultry populations. Conversely, in areas where Salmonella prevalence is very low (e.g. North EU countries), vaccination is generally not considered an effective control measure. Whereas, in some other geographical areas where Salmonella prevalence is non-negligible, vaccination remains one of the most used tools for the control of this pathogen. The use of vaccines against Salmonella must be economically sustainable. Therefore, their effectiveness must be high, costs should be reasonable, and the approach should be assessed in relation to the specific epidemiological situation in which it is applied.

  GAPS

  Assessment of the impact of controlling specific serovars through vaccination on the spread of other serovars. It would be valuable to quantify the real benefit of vaccination in different animal species in relation to the cost of the vaccination (cost-benefit analyses) and the epidemiological situation related to the presence/prevalence of Salmonella. Current vaccines are claimed to reduce infection and mortality in poultry and other species; however, they do not guarantee complete prevention of infection. As such, it is conceivable that infection may still occur and potentially lead to a carrier state, without the animal keeper being aware, as the animal may not exhibit clinical signs.

• Commercial potential for vaccines

  The use of Salmonella vaccines in poultry is mandatory in countries where a medium-to-high prevalence of infection is currently observed. In some countries, vaccination is a requirement under major industry-led assurance schemes, whereas in areas with low prevalence (e.g., Northern EU), it is generally not adopted or not allowed as a control measure for Salmonella. In the EU, S. Infantis, a serovar belonging to group C, is the most commonly isolated serovar from broiler flocks and poultry meat, particularly in certain geographical areas.

  GAPS

  Where poultry vaccination is already in place, there is a commercial potential for vaccines — particularly if they can be designed to be easily distinguishable from wild strains and also capable of preventing infection. Moreover, there is demand for DIVA vaccines that can be used during the laying phase Specific vaccines for S. Infantis In poultry, an affordable live attenuated vaccine against S. Infantis that can be used in broilers would be highly beneficial. Excretion of live vaccine strains The duration of excretion of vaccine strains after administration should be minimized to reduce the risk of contamination of the food chain. There is a great potential for development of multivalent Salmonella vector vaccines to a range of organisms if objections to Genetically Modified Organism (GMO) vaccines can be overcome

• Regulatory and/or policy challenges to approval

  There is currently a surveillance scheme in Europe for Salmonella in poultry. According to current legislation, any vaccine that cannot be distinguished from wild strains will not be approved for use. For the other species, there are no specific requirements in relation to the use of vaccines

• Commercial feasibility (e.g manufacturing)

  Vaccination of poultry is already diffuse, particularly in those geographic areas, where the Salmonella prevalence is non-negligible. There is no reason to believe that there will be a problem with new commercial vaccines. The main limitation is the size of the market in relation to development and authorisation costs, especially for species different from poultry, where the use of vaccination is generally focused on the farms with clinical manifestation of the infection.

  GAPS

  It would be useful to have a comprehensive list of countries that use vaccination - as well as the extent of use - in different animal species, in relation to their specific epidemiological situation and the available vaccines.

• Opportunity for barrier protection

  There is no barrier protection at the national level, but it can be applied at the level of individual holdings. In several EU countries, there are restrictions on the slaughter and marketing of Salmonella-positive poultry flocks. Under national control programmes, each batch of animals sent to slaughter is accompanied by a food chain information document, in which any positive test results must be declared. These carcasses are likely to undergo heat treatments or additional control measures, such as being slaughtered at the end of the day (prior to the cleaning and disinfection of the plant), or be redirected for the production of heat-processed meat, etc. The risk is managed according to the abattoir’s HACCP plan. Regarding pigs, based on the experience of one Nordic country, there are no penalties for live pigs. However, for breeding and multiplier pig herds with officially documented presence of Salmonella, challenges may arise when selling breeding stock and weaner pigs.

• Opportunity for new developments

  The aetiology of Salmonella is multi-factorial, and so is the solution. Feed additives as acidifier, prebiotics, probiotics, symbiotics, bacteriophages, etc., have opportunities for development.

• Pharmaceutical availability

• Current therapy (curative and preventive)

  In most cases, Salmonella results in an asymptomatic infection in livestock, so pharmaceutical treatments are used in rare situations only, e.g., to treat calves suffering from a clinical form of the infection. Antibiotic treatment of flocks of poultry is not permitted for control of Salmonella, unless there is a welfare implication or rare genetic stock would be lost if culled. Also, for other animal species, antibiotics are not used to treat infected animals. Due to the emergence of antibiotic multi-resistant Salmonella strains, the successful control of Salmonella spp. is fundamentally based on the use of Good Farming and Good Hygienic Practices from stable to table. The approach for controlling Salmonella is characterized by applying several intervention strategies that work synergically to minimize contamination risks. Control starts at the farm and includes qualified management in connection with strict cleaning and disinfection, pest control and strict biosecurity also for the feed. Moreover, within-herd spreading of Salmonella may be reduced by the use of certain kinds of feed, prebiotics, probiotics and competitive exclusion agents of organic acids added to feed or water. The development of new and successful bacteriophages active against Salmonella in poultry and pig production is a promising tool for food preservation and safety. The most effective methods for preventing and controlling Salmonella spp. infections, at the farm level, are the implementation of biosecurity measures and good farming practices. In terms of good farming practices, the most promising measures include: i) cleaning and disinfection procedures (using effective detergents, ensuring complete removal of organic matter, applying disinfectants at the correct concentration, and using high-quality cleaning water, and allow time to dry); ii) pest control through bait rotation and continuous monitoring; iii) strict and continuous sanitation of drinking water throughout the production cycle; iv) vaccination using a combination of live and inactivated vaccines; v) use of correct feed and various feed fortifications (e.g., organic acids).

  GAPS

  Effective interventions and assays for approval of alternative products to antibiotics are essential for the prevention and control of Salmonella. The established approaches for preventing and controlling Salmonella in live animals could be complemented by new cost-effective and efficient tools, such as the use of bacteriophages and the study of animal microbiota to promote its beneficial modulation. For each livestock species, it should be made clear how introduction of infection and subsequently spread could be prevented, as this might differ between species. Different serovars may respond differently to control measures. Thus, tailored approaches could potentially enhance the effectiveness of the implemented interventions. For some serovars, conventional cleaning and disinfection procedures are ineffective. Hence, there is the need for new, effective, and environmentally friendly disinfectants. Bacteriophages have shown promising results as biosanitizers, capable of reducing Salmonella contamination and disrupting mature biofilms. Their use has not been yet authorized in Europe (while other countries apply bacteriophages widely). Control of Salmonella is based on prevention through application of biosecurity measures. No single intervention (such as use of bacteriophages) will constitute an economically feasible way of controlling Salmonella, once introduced. Instead, a combination of efforts dealing with external and internal biosecurity is needed before a sustainable effect can be expected. In pigs, feed composition is important for the gut conditions that might be more/less conducive to Salmonella growth and, hence, spreading after introduction. Hence, correct feed, probiotics and acids etc can help keep down the within-herd prevalence. With the aim of reducing bacterial pathogens and promote the growth of beneficial microorganisms different strategies (e.g. competitive exclusion cultures, probiotics, prebiotics, symbiotic, organic acids, bacteriophages, modulation of the feed) can be developed with the final aim of modulating intestinal microbiota and create a gut environment unfavourable for the colonization of Salmonella. Manipulating the intestinal microbiota has emerged as an interesting strategy for preventing intestinal infections, promoting overall health and performance of animals. Equally important, a constant focus on slaughter hygiene is required to prevent meat contamination; this is relevant for all livestock species. Also in this phase of the production chain the implementation of effective procedures to control the spread of Salmonella is another valuable measure to be developed and tailored according to the specific situations.

• Future therapy

  The use of antibiotics and supportive therapy (e.g. rehydration, antisera, anti-inflammatories) will continue to be used in the cases of severe infections. However, any new antibiotics to which the bacterium has not yet developed resistance will probably be restricted to use in human medicine for the foreseeable future.

  GAPS

  Farm-specific alternative treatments to antibiotics.

  To prevent Salmonella infections in different species, correct feed and effective cleaning and disinfection procedures are required. Moreover, new disinfectants, competitive exclusion products and other products to modulate gut microbiota, as well as new bacteriophage cocktails should be developed.

• Commercial potential for pharmaceuticals

  In animal production, antibiotics are perceived to be of limited use. There may be some potential for use of antibiotics in humans.

  GAPS

  As a general protection of the gut and the intestines is needed, there might be a potential for a cost-effective medicinal, which can be orally administered, and able to foster protection against different pathogens including Salmonella (e. g Lawsonia, E. coli and Salmonella).

• Regulatory and/or policy challenges to approval

  The production of new antibiotics would be commercially feasible for use in humans but is unlikely to be so for use in animal production.

  GAPS

  Bacteriophages (phage-therapy) continue to gain attention due to their potential ability to selectively infect and kill Salmonella strains, representing a way of reducing its prevalence in animal populations without negatively impacting the microbiota essential for animal health. Although use of bacteriophages in live animals is allowed in other regions of the world (e.g. Russia and USA), they are not allowed in the EU. A guideline has been recently published by EMA to establish the regulatory/technical and scientific requirements applicable to veterinary medicinal products, specifically designed for phage therapy in livestock and composed of bacteriophages (EMA, 2023).

• Commercial feasibility (e.g manufacturing)

  The production of new antibiotics would be commercially feasible for use in humans but is unlikely to be so for use in animal production.

• New developments for diagnostic tests

• Requirements for diagnostics development

  Multiple-organism tests that can detect and characterise organisms rapidly. Improving availability of subtyping data for their epidemiological relevance in different contexts.

  GAPS

  Development of new diagnostic tests which also cover unconventional matrices could be valuable. Whole genome sequencing and applications of genomics could be set up on a routine basis in diagnostic laboratories since these methodologies are superior to existing methods for diagnosis, epidemiological studies, and surveillance of different Salmonella spp.

• Time to develop new or improved diagnostics

  This is dependent on the type of method and the level of research required, but considerable time is probably required.

• Cost of developing new or improved diagnostics and their validation

  All proof-of concept standards must be validated and ISO 16140 series can be followed for this scope. Hence, validation would be needed by the reference laboratories. This implies that the cost of diagnostics could be substantial.

• Research requirements for new or improved diagnostics

  In the EU, it is common to use molecular methods for Salmonella detection in food samples (both as own check and official controls), whereas the use of molecular approaches for diagnostic purposes in animal samples is less common. In general, diagnostic laboratories use microbiological methods, and based on this, they carry out serotyping, MIC and other investigations from the Salmonella isolates identified.

  GAPS

  New multiple organisms tests for rapid detection and characterisation could be most useful. Development of biosensors to rapidly detect Salmonella from different samples would be most welcome. Practical test regimes should be developed involving tests with high sensitivity to be used in combination with high specificity ones to analyse positive samples. Fast and reliable PCR-based detection methods should be developed to reduce the number of days needed for isolation and for use as screening and isolation with traditional bacteriology for positive samples. Reliable and rapid methods for Salmonella detection using unconventional matrices such as aerosol are needed. ​​Salmonella quantification from different matrices would be helpful.​

• Technology to determine virus freedom in animals

  Not applicable.

• New developments for vaccines

• Requirements for vaccines development / main characteristics for improved vaccines

  An innovative area of interest is the use of reverse vaccinology, a genomic approach to identifying novel antigen targets for vaccines. While this method has identified several promising vaccine candidates, the majority of these antigens have only undergone in silico (computer-based) analysis, and only a small number have been tested in live animal models. Those that were tested showed statistically significant protection, suggesting strong potential, though more preclinical trials are needed. New research has revealed that various vaccine candidates (through reverse vaccinology, mutant-attenuated vaccinology, subunit vaccination, bacterial ghost vaccines) could pave the way for commercial vaccine preparation.

  GAPS

  In the geographical areas where the prevalence of Salmonella is non-negligible, the availability of multiple-serovar vaccines, especially for S. Infantis, could be a valuable tool for controlling multiple infections in poultry flocks. Moreover, the availability of vaccines against S. Infantis could be important to reduce the colonization of broiler flocks with this pervasive serovar that can persist under and adapt to broiler flocks in diverse environmental conditions. Due to S. Infantis high prevalence in some geographical areas in the EU, specific vaccines for this serovar could be valuable. Moreover, multi-resistant S. Kentucky is also a matter of concern. Thus, vaccines could be useful for these emergent serovars. Improved programmes for best use of existing vaccines should be developed specifically for the areas where use of vaccination is considered as an effective tool to control Salmonella.

• Time to develop new or improved vaccines

  The time to develop a vaccine along the lines above would be considerable, not only for the development of the vaccines, but also for convincing the authorities and the public to accept the principle of genetically modified organisms.

• Cost of developing new or improved vaccines and their validation

  This could be substantial especially if a lot of time and energy was spent in convincing the general public regarding genetically modified organisms.

  GAP

  For the different animal species in relation to the prevalence of the pathogen and the circulating strains. a cost-benefit analysis about the effect of vaccination and the economic impact could be useful.

• Research requirements for new or improved vaccines

  As above – plus social science investigation into vaccine acceptability - the GMO argument is likely to be largely old dogma now.

• New developments for pharmaceuticals

• Requirements for pharmaceuticals development

  The most promising developments involve alternatives to pharmaceutical antibacterials, as well as other strategies to prevent Salmonella colonization and infection. Bacteriophages could represent an effective alternative for controlling Salmonella. Promising areas of development also include new prebiotics, probiotics, bacteriocins, and competitive exclusion products.

  GAP

  There is interest in products that provide a general protective effect on the gut and intestines. The products to be developed should be administered orally, be low-cost, and have a documented effect not just against Salmonella but preferably also against other pathogens.

• Time to develop new or improved pharmaceuticals

  The development and licensing of new pharmaceuticals is a time consuming business It should be investigated how the authorisation process could be faster.

  GAP

  A fast authorisation process is welcome but it must not be at the expense of showing effect on-farm outside the lab. Moreover, the side effects need to be known.

• Cost of developing new or improved pharmaceuticals and their validation

  This could be substantial especially if a lot of time and effort was spent.

  GAP

  A broad application targeting prevention will help to ensure a large potential market, whereby the costs associated with development can be spread on a higher volume.

• Research requirements for new or improved pharmaceuticals

  As above.

  GAP

  Any new medicinal product must be safe to use, should not induce resistance, should have a broad-spectrum effect, and must be easy to administer (e.g., orally) and be cheap.

Disease details

• Description and characteristics

• Pathogen

  For named serovars, to emphasize that they are not separate species, the serovar name is not italicized and the first letter is capitalized. As for genus, species and subspecies the traditional italicized font is kept. In Salmonella enterica serovars, S. Enteritidis and S. Typhimurium and its monophasic variant are highly pathogenetic.

  GAPS

  IT would be valuable to know serovars variability in different countries and variability within a serovar. Spread of emerging serovars: for example, the monophasic Salmonella variant of Typhimurium and the emergence of a new variant of S. Infantis lacking the somatic antigen, and others showing success in different epidemiological niches.

• Variability of the disease

  Among Salmonellae, there are more than 2,500 serovars, although the two most commonly associated with human food poisoning are those mentioned above. Other S. enterica serovars have specific hosts — for example, S. Abortusovis in sheep. Some tend to be associated with certain hosts but can also infect others, including humans. For example, S. Dublin infects cattle, sheep, humans, and, more rarely, poultry, but all appear capable of causing varying degrees of disease in most mammalian species. Additionally, there is a significant reservoir of antimicrobial resistance among these serovars.

  GAP

  Limited knowledge of virulence factors and their relevance, host-pathogen interaction Identification of clones associated with virulence and ability to spread in different epidemiological niches and molecular drivers associated with their epidemiological success.

• Stability of the agent/pathogen in the environment

  Salmonella can survive for months outside a living body and have been found in dried excrement or contaminated feed after over 2.5 years. Ultraviolet radiation, heat and moisture accelerate their demise.

  GAP

  Infectivity of environmental survivors. Capability of the different serovars - clones to persist in the environment and genetic mechanisms (molecular drivers) implicated in their persistence.

• Species involved

• Animal infected/carrier/disease

  Salmonella remains prevalent worldwide in both warm and cold blooded animals but also in non-living environments. The symptoms of disease in animals vary according to the serovar involved and infection may be asymptomatic or symptoms may be mild enough to be missed, but equally may be severe enough to kill. Once infected, even if recovered, some animals may continue to shed the bacteria for extended periods, certain serovars for years afterwards. Carriage and recycling of infection between older and younger or recently introduced animals or between livestock and wildlife vectors is common.

  GAPS

  Lack of -multi-year, quantitative data on Salmonella persistence in mixed-species ecosystems (e.g., farms with livestock and wildlife interactions); -studies about molecular drivers of long-term asymptomatic carriage in production animals (e.g., poultry, pigs) and their role in maintaining antimicrobial-resistant (AMR) strains; - studies about impact of urban wildlife (e.g., rodents, birds) on AMR Salmonella transmission to livestock, particularly in intensive farming systems.

• Human infected/disease

  Humans are predominantly infected via ingestion of contaminated food but can also become infected as a result of direct contact with animals, especially cattle or pets, or by contact with environments contaminated with faeces, including contamination caused by infected cats and wildlife. Cross contamination of food during processing or preparation is a major risk factor. Non-typhoidal Salmonella causes over 91,000 cases annually in the EU. It is estimated that the worldwide burden is much higher, causing approximately 93.8 million cases of gastroenteritis and around 155,000 deaths each year.

  GAPS

  There is an ongoing need for more precise risk ranking of food and non-food sources, especially in light of changing food production systems and global trade. The role and prevalence of asymptomatic infection in humans, and their contribution to ongoing transmission, particularly in community and occupational settings deserves to be further investigated. The burden of disease should be more consistently estimated using metrics such as disability-adjusted life years (DALYs). Moreover, source attribution studies should be updated using whole genome sequencing (WGS) to better inform targeted interventions than seen when using current methods. The impact of non-livestock animal sources (e.g., pets, wildlife) on human salmonellosis requires further investigation, especially as pet ownership and urban wildlife interactions increase.

• Vector cyclical/non-cyclical

  On farms rodents, wild birds and insects may act as vectors along with the carriage of Salmonella on overalls, boots and hands of farm workers. Backyard poultry and irrigation water may also serve as key vectors. Anyone who handles the carcasses of animals may also act as a vector along with mechanical objects used either in farms or in food processing facilities. Aquatic vertebrates and reptiles kept as pets may also act as vectors.

  GAPS

  Quantitative assessment of the relative risk posed by different vectors, including the infectious doses associated with each, remains incomplete. The role of environmental persistence and indirect transmission (e.g., via water or fomites) in sustaining outbreaks is not fully characterized, especially under varying climate and management conditions.

• Reservoir (animal, environment)

  Salmonellae are relatively common in the natural world and therefore any animal or environment may act as a reservoir anywhere in the world. Some serovars have spread within certain animal species or production sectors (e.g. S. Choleraesuis in pigs or S. Enteritidis in laying hens) thus permitting further spread into the environment. The act of spreading animal manure on land as fertilizer and wash water for irrigation can contaminate crops also.

  GAPS

  The genetic and management factors underlying serovar adaptation and persistence in specific hosts or production systems are not fully understood. The impact of environmental reservoirs, including soil and water, on the epidemiology of Salmonella, particularly in the context of climate change and agricultural intensification, requires further studies.

• Description of infection & disease in natural hosts

• Transmissibility

  Salmonella transmission occurs both horizontally (e.g., faecal-oral route) and vertically (e.g., contaminated eggs in poultry). Salmonella has also been isolated from the litter and dust from poultry houses. Most animal infections result from spread by carrier animals or contaminated feed. In poultry the hatchery is also an important potential source.

  GAPS

  Relative risk attributable to the different sources would be helpful. The relative contribution of different transmission routes (e.g., foodborne, environmental, direct contact) to overall disease burden is not well quantified. The impact of animal carriers on transmission dynamics, especially in food production and healthcare settings, is underexplored. The role of the food supply chain and cross-border trade in amplifying or mitigating transmission risks needs further investigation, particularly with the integration of WGS in surveillance.

• Pathogenic life cycle stages

  There are no specific life cycle stages involved although small numbers of organisms can survive in a dormant form that may be difficult to culture for long periods. Disease is caused by the rapid multiplication of the bacterium with secreted proteins permitting adhesion and invasion of the cells of the intestine with subsequent further proliferation causing an inflammatory reaction leading to dysentery. Invasion of intestinal cells is promoted by secreted proteins that subvert the host cells metabolic systems leading to internalisation of Salmonella cells and subsequent survival within macrophages. Systemic infection results from passage of viable organisms beyond the local lymph nodes into major lymphatics and the circulatory system. This is more likely with host-adapted strains in the relevant species.

  GAPS

  Detailed host-pathogen interactions in target species (beyond murine models) remain insufficiently characterized, particularly regarding immune evasion and persistence mechanisms. The molecular basis for differences in pathogenicity and host adaptation among emerging serovars and sequence types (e.g., ST313) is a key research priority.

• Signs/Morbidity

  Salmonellosis manifests usually as diarrhoea although clinical signs in animals can include septicaemia and abortion, as well as pneumonia and lesions of the distal extremities in calves. Acute cases in animals and poultry can lead to death and there is a serious loss of production. In humans the disease manifests itself by a watery and sometimes bloody diarrhoea, abdominal pain, fever, headache, nausea and vomiting.

• Incubation period

  The incubation period for Salmonella infection is generally 12 to 72 hours, but can vary with infectious doses, host features and involved strains.

  GAPS

  More detailed analyses are needed to correlate incubation period variability with specific serovars/strains, infectious doses, and sources.

• Mortality

  The infection is often manifesting itself only subclinically. However, the case fatality may be high among acutely infected animals that are showing symptoms, particularly cattle, and also among the young and elderly of the human population. Morbidity, case fatality and mortality can vary significantly between the species infected and also the serovar involved. The type of strain within a serovar is more important than the serovar itself (virulence factors).

  GAP

  Quantitative assessment of the impact of disease management in different animal species practices and concurrent diseases on mortality and case fatality is lacking.

• Shedding kinetic patterns

  Infection in most animals and humans resolves spontaneously within a period of weeks. Some animals that apparently recover from salmonellosis caused by certain serovars may become permanently infected and a small number may excrete the organism in their faeces for years. Others may harbour the infection in a latent form and only excrete the bacterium during periods of stress. Infection may circulate within an animal population, being passed on to newly introduced animals which then excrete high numbers of organisms that may overcome the ‘immunity’ of some previously exposed animals.

  GAP

  Details of shedding – variability, time and numbers – in food animals are valuable data to collect. Factors that trigger intermittent or stress-induced shedding episodes, and their epidemiological significance should be further investigated.

• Mechanism of pathogenicity

  Disease is caused by the rapid multiplication of the bacterium with secreted proteins permitting adhesion and invasion of the epithelial cells of the intestine and loss of fluid and blood from the intestine. Proteins that appear to protect the bacterium from destruction by macrophages are also present. Once the bacterium has attained its intracellular state the cell's metabolism is used to produce bacterial protein and bacteria can accumulate within membrane bound Salmonella containing vacuoles. Several serotypes of medical importance, including Typhimurium, Enteritidis, Newport, Dublin, and Choleraesuis, are known to harbour virulence plasmids containing genes that code for fimbriae, serum resistance, and other factors, but the full repertoire of virulence mechanisms is very complex, varying between serovars and clonal lines, and is still not fully understood. Systemic infection can result in sepsis within vital organs, bacteraemia and septic shock.

  GAP

  Identification of universal or serovar-specific virulence factors that could serve as effective subunit vaccine targets remains a major challenge.

• Zoonotic potential

• Reported incidence in humans

  The incidence of salmonellosis in the EU has remained relatively stable in recent years. In 2023, a total of 77,486 confirmed cases of salmonellosis were reported in the EU, corresponding to an incidence rate of 18.0 per 100,000 population. This makes salmonellosis the second most commonly reported zoonosis in the EU, after campylobacteriosis. (EFSA and ECDC, 2024) The most frequently reported serovar remains S. Enteritidis, accounting for more than 60% of all confirmed cases, followed by S. Typhimurium and its monophasic variants. The majority of outbreaks are still associated with eggs, egg products, and poultry meat, but outbreaks linked to pig meat and pig-derived products continue to be reported. While the overall trend since the early 2000s has been a marked decrease in cases - primarily due to successful control programmes in poultry - the number of cases has plateaued in the last decade, with no significant further decline. Occasional large outbreaks continue to occur, often linked to cross-border food distribution.

  GAP

  The true extent of underdiagnosis and underreporting in many countries is unknown.

• Risk of occurence in humans, populations at risk, specific risk factors

  The whole human population is at risk including those who work closely with cattle, have companion animals or are involved in the processing or consumption of food. The most serious cases are generally observed among infants, small children, the elderly and those with suppressed immunity. A more specific risk factor would appear to be an apparent lack of understanding of the need to maintain safe handling and storage of food, kitchen hygiene and proper cooking.

  GAPS

  The relative contribution of environmental versus foodborne transmission, and the role of asymptomatic carriers in high-risk settings (e.g., food industry, healthcare) should be further investigated. The impact of socioeconomic factors, urbanization, and changing dietary habits on risk profiles deserve further studies.

• Symptoms described in humans

  In humans, the disease manifests itself by a watery and sometimes bloody diarrhoea, abdominal pain, fever, headache, nausea and vomiting. In severe cases, septicaemia may develop and this can lead to complications which can give rise to conditions such as arthritis, septic aneurysms or other localised infections and osteomyelitis. Reactive arthritis and irritable bowel syndrome may also be sequels to enteric infection. Signs and symptoms of Salmonella infection generally last two to seven days. Diarrhea may last up to 10 days, although it may take several months before bowels return to normal.

  GAPS

  The true incidence and cost of long-term sequelae in humans (e.g., reactive arthritis, irritable bowel syndrome) and risk of premature death following infection are not well documented. The prevalence and impact of subclinical infection in humans, especially in high-risk occupational groups, remain unclear. Quantitative distribution of such symptoms in comparison with other causes of intestinal infectious disease (IID).

• Likelihood of spread in humans

  This is dependent on the level of hygiene among the population and spread of infection has been reported in care homes. Meticulous hygiene may prevent the spread from infected humans, but it is not uncommon for a breakdown in the hygiene to occur and for cases to become apparent. This is emphasised in Europe by the need to prevent people known to be infected from working in the food preparation industry. In less developed countries, the likelihood of spread is significantly greater especially where the sanitary treatment of human excrement is lacking. Salmonella can also survive in water and, thus, drinking water supplies may also become contaminated.

  GAP

  More knowledge about the detailed mechanisms of spread and doses involved would be most useful.

• Impact on animal welfare and biodiversity

• Both disease and prevention/control measures related

  Salmonellosis control measures, disinfection, removal of excrement, spreading of manure only on fields that are not going to be grazed for a significant period, will help to control outbreaks and also improve the welfare of animals. Statutory monitoring of the situation in breeding and production flocks of poultry also affects control of the disease. Vaccination and culling of infected flocks are also important control measures in poultry.

  GAP

  There is a lack of welfare studies in sick animals, and it would be of interest to have assessments of pain and pain relief.

• Endangered wild species affected or not (estimation for Europe / worldwide)

  Salmonellosis is widespread and worldwide and therefore there is no reason to believe endangered wild species would not be susceptible. However, the disease is usually associated with intensively reared livestock and the aftermath of such systems so it may be argued that wild species may not often come into contact with intensively reared livestock so the risk is minimised. Some wild animals, particularly reptiles, pigeons, small garden birds, badgers and hedgehogs carry specific types of Salmonella and there have been outbreaks of disease and deaths in finches caused by salmonellosis. Wild birds may also act as reservoir for spreading the infection within the farms rather than being the primary source of introduction of the infection.

  GAP

  More information about the role in wild bird fluctuations and the role of rodents in contamination of endangered species consuming rodents would be welcome.

• Slaughter necessity according to EU rules or other regions

  During outbreaks, especially if humans are infected, those animals that are harbouring the pathogen and acting as a reservoir, are often subject to culling or compulsory slaughter. However, the infection itself is not normally associated with compulsory slaughter of large numbers of animals or birds. Except in the case of breeding chickens or turkeys when S. Enteritidis or S. Typhimurium or other relevant serovars are confirmed or in certain countries where a ‘stamping out’ policy for most Salmonella infections is in force for one or more of the food animal species. Moreover, when infections are caused by very invasive serovars (e.g. S. Choleraesuis in pigs, or S. Gallinarum/Pullorum in poultry), in some geographical areas affected animals are culled and the producer is compensated.

  GAP

  Impact of culling versus restrictions (slaughtering) in relation to the epidemiological situation (e.g. prevalence /circulating serovars-strains) deserves further investigations.

• Geographical distribution and spread

• Current occurence/distribution

  Worldwide.

  GAP

  It would be interesting to know the reason for the global spread of some strains but not others.

• Epizootic/endemic- if epidemic frequency of outbreaks

  Endemic – with periodic emergence of specific epidemic strains about every 10 years.

  GAP

  Likewise, the reasons for rise and fall of epidemic strains is largely unknown. A methodology for source identification of new emerging strains would be welcome.

• Speed of spatial spread during an outbreak

  To minimise spatial spread, risk factors in the environment should be identified and managed, e.g., by focusing on the biosecurity standards of the farms. Among young animals, especially those in intensive rearing situations, the spread of the disease can be fast, in particular in poultry but less so in pigs. The spreading between poultry holdings can also be rapid if carrier animals are distributed widely. The spread of the disease within a flock and the flock's sensitivity to high levels of healthy carriers depends on the population density of laying hens. In pigs, the replacement of infected breeding pigs will result in spreading of the infection.

  GAP

  Quantitative data to populate transmission models are needed.

• Transboundary potential of the disease

  Salmonellosis has been readily spread across geographical boundaries , for example from breeder birds to layers and broilers and among calves taken to market and sold to calf rearers. Contract spreaders of manure may also be responsible for the spread of salmonellosis if the manure has not been treated or the machinery carefully disinfected between farms. Spread between holdings and countries can also be rapid if carrier animals, e,g, replacement breeding pigs or hatching eggs, are distributed widely. Some cases related to exchange between EU member states, of contaminated straw used for animal litter were identified as a source of infection with S. Enteritidis in poultry flocks.

  GAP

  It would be valuable to obtain more data about strains variation in spread ability.

• Route of Transmission

• Usual mode of transmission (introduction, means of spread)

  The faecal-oral route is the normal mode of transmission among animals and for humans this route may also be important but the more accepted route of transmission to humans is via the consumption of contaminated food.

  GAPS

  More information about the quantification of infectious doses from different matrices and exposure routes would be welcome.

• Occasional mode of transmission

  Among intensively reared poultry, the vertical transmission via the egg is a recognised route of transmission, probably due to a special affinity of some strains to the uterine mucosa of hens. Contamination of collected semen, e.g. from turkeys is also possible. Airborne spread may also occur via contaminated dust or aerosols.

  GAP

  More information about the relative risk of airborne spread is needed.

• Conditions that favour spread

  Intensive rearing of animals and poultry and lack of suitable hygiene procedures, especially all-in/all-out production and disinfection of housing between batches are the conditions favouring spread. Spread of Salmonella clones which have developed adaptive mechanisms, which favour their persistence in different environments.

  GAP

  Validated procedures for establishing and maintaining minimal level of within-herd prevalence of Salmonella on large farms – especially pig farms would be welcomed.

• Detection and Immune response to infection

• Mechanism of host response

  The innate immune system is involved initially and this is followed by both humoral and cellular immune responses, since Salmonella induces a strong inflammatory response, characterized by recruitment of neutrophils and macrophages. These cells attempt to phagocytose and kill the bacteria, although Salmonella can survive within macrophages in specialized vacuoles. Immunoglobulins are produced and these may eventually aid the clearance of the bacterium. It should be borne in mind that the clearance is often not complete, since it can interfere with autophagy and inflammatory pathways to promote its survival. Stress situations can elicit a recrudescence of the bacterium suggesting that it has adapted to maintaining an intracellular presence despite the immune responses.

  GAPS

  Better studies about the genetic factors that can enhance resistance to infection by modulating immune responses in poultry. Better studies about the role of commensal bacteria and short-chain fatty acids (SCFAs) and probiotics in developing resistance to Salmonella infection and colonization. Better studies about the interaction between Salmonella and the gut microbiota: the role of specific gut bacteria in combating Salmonella and how these interactions can be used for therapeutic purposes. Also the influence of different diets on the gut microbiota and the Salmonella infection dynamics need better understanding.

• Immunological basis of diagnosis

  A number of serological tests are available for the diagnosis of salmonellosis. Whole blood tests and serum agglutination tests have been used for long periods and ELISAs are now in routine use. Depending on the antigen and tests used, serological cross reactions between different serovars and even with some non-Salmonella organisms can occur so bacterial isolation must be used for confirmatory diagnosis.

  GAP

  Tools to assess cellular and local response could be valuable. Achieving a vaccine that targets different Salmonella serotypes is still a challenge.

• Main means of prevention, detection and control

• Sanitary measures

  Feed, food and water should be treated prior to consumption. Manure should be composted or effectively treated prior to being spread on the ground. Cleaning and disinfection of the environment where animals are kept and of items coming into contact with either the animals or their excreta should be practised. Rigorous adherence to sanitation will minimise the risk but not prevent it completely. General biosecurity measures remained a good means to avoid introduction of Salmonella into farms.

  GAPS

  Potential for applying competitive exclusion principles to overcome environmental contamination. Enhanced cleaning and disinfection protocols especially to control serovars that have demonstrated high persistence and tendency to be transmitted from a cycle to the next. Different serovars may respond differently to control measures so tailored approaches can enhance the effectiveness of the implemented interventions. Role of the biogas plants to the maintenance of Salmonella in the environment. Persistence of Salmonella in the environment when contaminated manure-slurry is used as soil amendment in relation to the Salmonella strains and environmental conditions. Shared biosecurity standards to avoid introduction and dissemination of Salmonella in different animal species and farm systems.

• Mechanical and biological control

  The isolation or elimination of animal carriers and the prevention of cross contamination together with adequate disinfection permits a good but incomplete degree of control. Biosecurity measures should be implemented at the farm level to prevent the introduction and spread of Salmonella, and at the slaughterhouse as part of hygiene practices to avoid cross-contamination of carcasses. In certain cases, for example, in pig production in some countries, there is no requirement for Salmonella eradication at the farm level, provided that the slaughterhouse maintains a high standard of hygiene, effectively preventing the dissemination of Salmonella and carcass contamination.

  GAPS

  Social science studies to understand barriers and motivators of farm staff implementing consistently biosecurity measures, both externally and internally. Establish effective cleaning and disinfection protocols, using appropriate disinfectants and ensure knowledge about the importance of sufficient drying time.

• Diagnostic tools

  Bacteriological methods for Salmonella isolations (based on ISO 6579:1) - isolates can be then serotyped - typed (WGS) - tested for antimicrobial susceptibility. Whole blood tests and serum agglutination tests are still used along with ELISAs which have been validated. Cross reactivity among the serovars often occurs and therefore a definitive diagnosis of the serovar concerned involves isolation of the organism using bacterial culture methods.

  GAPS

  Better methods to simultaneously and rapidly detect, type and characterise organisms. Semi-quantification by qPCR methods Typing by NGS for different epidemiological investigations even though the method is still costly Investigation of less invasive sampling methods such as environmental sampling and pooling for bacteriological methods and saliva sampling for antibody detection.

• Vaccines

  Many inactivated vaccines are used against salmonellosis. Live vaccines have also been used in several countries. In other countries (e.g., in Northern Europe), where Salmonella prevalence is very low, vaccination is not employed as a tool for Salmonella control. Mutant vaccines, attenuated through rational gene deletion techniques using molecular biology, have also been developed. EU legislation requires that live vaccines for poultry must not be used unless a suitable method is available to bacteriologically distinguish wild-type Salmonella strains from vaccine strains.

  GAP

  As above

• Therapeutics

  The use of antibiotics for treating animals and humans with salmonellosis is limited in many countries due to the risk of increasing antimicrobial resistance in the bacterium. Antibiotic treatment is generally restricted to cases where the disease is severe and potentially life-threatening. EU legislation states that antimicrobials shall not be used as a specific method for the control of salmonellosis in poultry.

  GAP

  As above

• Biosecurity measures effective as a preventive measure

  The checking of feed and water for the presence of Salmonella and the provision of dedicated protective clothing, hygiene barriers, and disinfection together with proper handling of excreta is appropriate. Where possible replacement animals or birds should be placed in quarantine before moved onto the farm and, where this cannot be avoided pre-movement testing at source is advisable. Moreover, replacement animals should be otherwise isolated and monitored .

  GAPS

  Farmers should be motivated to establish and use quarantine on-farm for replacement animals. Moreover, farm staff should ensure full compliance. Studies about reluctance to do so are lacking How can social science be better integrated to improve compliance with biosecurity standards? Implementation of interactive tools to engage farm personnel in biosecurity.

• Border/trade/movement control sufficient for control

  The general prevalence of Salmonella organisms alone would not justify restricting cross-border trade. However, current surveillance in poultry suggests that infected animals would not be acceptable for trade. Similarly, animals known to be infected would also be rejected. There is still room for improvement, as frequent breaches in control occur involving animals from both within and outside the EU. In some Northern European countries, successful efforts to combat Salmonella have resulted in special guarantees being required when other countries export broiler meat and eggs to them.

  GAP

  Design of reliable testing regimes for international trade and detection of masking by antibiotic treatment.

• Prevention tools

  Biosecurity, the use of disinfection and normal sanitary measures can be used, but no method is 100% effective at preventing spreading of Salmonella because of the common occurrence of the organism and the high cost of intensive control programmes. Also, at the abattoir high hygiene procedures are implemented. The industry employs counterflow systems, multi chamber scalders, singeing/flambation, decontamination and other advanced technologies. Processing includes multiple washing steps, and the use of antimicrobial chemical spray treatments helps reduce Salmonella and the risk of cross-contamination. Effective singeing and blast chilling during cooling also contribute significantly to reducing Salmonella. Some abattoirs additionally implement decontamination steps. For example, some abattoirs have previously used hot-water decontamination for pigs originating from herds with the highest Salmonella burden, however, this has recently been abolished as it was not perceived as cost-effective.

  GAP

  Define cost-effective priorities among the possible strategies for Salmonella control along the production chain (farm and abattoir) in relation to the different epidemiological situations.

• Surveillance

  The EU has a specific surveillance procedure in place for monitoring the level of S. Enteritidis and S. Typhimurium infection in poultry with specific targets in terms of the percentage reduction to be achieved for breeding chickens, laying hens, broilers and turkeys. For other animal species, the situation varies greatly among different countries. In some countries, control plans and surveillance programs have been actively implemented for several years by industry or government, while in others no plans have been activated so far. Regarding pig production, the only requirement which was strengthened in 2014, after years’ of negotiations, was the microbiological process criterion for Salmonella on pig carcasses. The same criterion on carcasses has been implemented also for other animal species.

  GAPS

  Verification of improved prevalence in countries with active control plans. Cost–benefit analysis of the implemented control plans. Source attribution studies to identify the animal categories/priorities that should be covered by control plans.

• Past experiences on success (and failures) of prevention, control, eradication in regions outside Europe

  Surveillance and slaughter techniques with poultry have reduced the number of human infections from eggs or poultry meat considerably, since the inception of this method of control. However, there is no easy means of eradicating the infection, and a varying level of infection still persists in most MS. Sweden, Norway, Finland and Denmark have achieved a very high level of control by means of stamping out and restrictions as well as intense feed controls, but as the size of farms increases such measures become increasingly unaffordable. For instance, in other sectors, such as pigs in Denmark, instead of an elimination strategy, a reduction strategy is implemented, where the focus of control is on the meat processing phase of production.

  GAPS

  How to create and maintain Salmonella-free niches in mainstream production.

• Costs of above measures

  The cost of the ‘Salmonella in eggs scare’ in the UK in the early 1990s, which led to increased surveillance and slaughter of birds, is estimated at £70 million. While the current annual cost is likely lower due to fewer infected poultry flocks being slaughtered, the ongoing cost of surveillance remains considerable and, since it is now EU-wide, may even exceed the figure mentioned above. The continued expenses for the EU, producers, and competent authorities in control programmes are substantial but necessary to maintain market confidence. Public health gains have not translated into direct benefits for the industry. In Denmark, the extensive measures taken in poultry to keep Salmonella out have required massive investments but are still perceived as worthwhile, as they have resulted in an EU-accepted “Salmonella-free” status. This status implies special guarantees, sets requirements for countries exporting to Denmark, and opens access to valuable export markets. Moreover, Denmark has operated an extensive pre-harvest programme in pigs for decades, similar to several other Northern European countries. However, this programme was stopped in 2024 because it was not perceived as cost-effective, and therefore replaced with a programme with an increased focus on hygiene during slaughter.

  GAPS

  The EU cost benefit analyses to assess the value of national control programmes in livestock were done in the early 2000s. As things might have changed, this represents a data gap. It might be relevant to reassess the effectiveness of Salmonella national control programmes in place in the different European countries. Looking at data published in the last EFSA_ECDC zoonoses report (2024) it is clear that in the most recent years (last 5 years) no variations were seen in terms of prevalence of Salmonella spp. and relevant serovars in the different poultry populations.

• Disease information from the WOAH

• Disease notifiable to the WOAH

  Salmonellosis is not an OIE notifiable disease.

• WOAH disease card available

  https://www.woah.org/app/uploads/2022/02/salmonella-enterica-all-serovars-infection-with.pdf

  GAP

  Not applicable

• WOAH Terrestrial Animal Health Code

  Not available.

  GAP

  Not applicable

• WOAH Terrestrial Manual

  https://www.woah.org/fileadmin/Home/fr/Health_standards/tahm/3.10.07_SALMONELLOSIS.pdf

  GAP

  Not applicable

• Socio-economic impact

• Zoonosis: impact on affected individuals and/or aggregated DALY figures

  In general, the impact on human individuals is most often a case of dealing with diarrhoea for a few days. Where the disease progresses, antibiotic treatment may be required and ultimately hospitalisation. Occasionally the disease may be severe in the very young or elderly, and in a few cases it may be the cause of death. Non-typhoidal Salmonella and invasive non-typhoidal Salmonella (iNTS) infections collectively accounted for approximately 8.28 million disability-adjusted life years (DALYs) worldwide (Kim et al. 2024). The FERG Report from 2015 contains relevant data from the entire world and estimated that Non-typhoidal Salmonella was responsible for approximately 4.0 million disability-adjusted life years (DALYs) worldwide (PRINT-1347-OMS-FOS-FERGreport-20160408.indd).

  GAP

  To assess the relevance of different sources for Salmonella infections. Salmonella risk ranking and identification of priorities for food safety resource allocation at EU level and for each country.

• Zoonosis: cost of treatment and control of the disease in humans

  In the United States, non-typhoidal Salmonella infections contribute to approximately 1.2 million illnesses annually, leading to increased medical costs and extended recovery times due to antimicrobial resistance (Davidson et al. 2018). Data from USDA’s Economic Research Service (ERS) show the total cost for foodborne Salmonella infections in the United States is a staggering $4.1 billion annually and the cost for the loss of productivity to the economy is $88 million. The European Food Safety Authority (EFSA) estimates that over 91,000 cases of salmonellosis are reported annually within the EU, with an associated economic burden potentially reaching €3 billion each year.

  GAP

  A detailed breakdown of treatment costs by Member States (MS), along with differences in antimicrobial use and treatment failure rates in MS with high levels of antimicrobial resistance (AMR), is needed. A cost–benefit analysis of EU measures against Salmonella should be conducted again to investigate what (and where) the value of investing in Salmonella prophylaxis is, and where control strategies should be strengthened, including biosecurity measures. The EU cost–benefit analysis previously conducted on pigs and pork (SANCO/2008/E2/036) did not demonstrate that the benefits outweighed the costs. However, as many years have passed since that assessment, it is advisable to repeat the analysis, taking into account the current epidemiological situation.

• Direct impact (a) on production

  In poultry, the cost of production is ascribed to the cost to the farm of replacing birds slaughtered because they are found to be positive for Salmonella together with the costs of cleaning and disinfections procedures and vaccination. The cost, therefore, may be high. Deaths and clinical disease resulting in large costs may interest cattle, but also occur in sheep, whereas in pigs and poultry this is observed only infrequently. In the poultry sector, non-typhoidal Salmonella associated with chickens imposes an estimated annual economic burden of $2.79 billion globally (Shaij et al., 2023).

  GAP

  In general, the perception is that there is not much of an impact in particular in pig production but also in other species, probably because most infections are subclinical. Therefore, an accurate estimate of the actual cost in the different species and epidemiological situations could potentially increase awareness of the true extent of the problem.

• Direct impact (b) cost of private and public control measures

  There are a number of estimates of the cost of surveillance depending on which country is recording the cost but generally it is thought that the cost of surveillance alone is about​​ £ 3.4 million per annum. Also private control measures, including biosecurity, vaccination and nutritional strategies, are effective but may require financial incentives to ensure widespread adoption in the EU (Fraser et al., 2014).

  GAP

  More detail needs to be gathered from European Commission claims for reimbursement. Social and economic research is needed to evaluate attitudes of farmers to the control of animal infections that have little or no impact on the animal, but which may have food safety implications for humans, as Salmonella, first to assess the impact of various biosecurity interventions on the risk of infection

• Indirect impact

  The total cost of the ‘Salmonella in eggs scare’ in the UK in 1993 has been estimated at £70 million based on the cost of slaughtering infected birds and the 90% drop in consumption of eggs. Other reports of Salmonella (e.g. in pigs) appear to not have disrupted the market in the same way (Mu et al. 2024).

  GAP

  No overall cost benefit analyses of Salmonella prophylaxis have been done at an EU level. For pigs, this has been made: SANCO/2008/E2/036, but it is advisable to update the analyses according to the current epidemiological situation in the different geographical areas

• Trade implications

• Impact on international trade/exports from the EU

  Other than the obvious restriction on infected animals there are no further restrictions on the international trade for this disease. Imports into the EU must conform with EU control legislation and countries must be approved for such imports. Certain third countries have additional requirements in relation to testing of breeding stock, companion animals and horses. At the EU level, Scandinavian countries (e.g. Sweden, Finland and Denmark) have special guarantees in relation to the introduction of pig, bovine and poultry meats due to their Salmonella status. Regarding poultry, Denmark has an advantage because the so-called free status allows the country to set up special requirements when eggs are imported. Similarly, the free status has allowed Danish poultry/egg producers to get access to valuable export markets.

  GAP

  Role of international trade in spreading infection – e.g. in pigs. Some countries like Sweden and the Netherlands have prevented outbreaks by strictly controlling imported breeding stocks, but these practices are not universally adopted. Most genomic surveillance studies focus on outbreaks rather than trade-related transmission pathways (Li et al., 2021).

• Impact on EU intra-community trade

  Other than the obvious restriction on infected animals there are no further restrictions on the international trade for this disease.

  GAP

  Same answer as above

• Impact on national trade

  Other than the obvious restriction on infected animals there are no further restrictions on the international trade for this disease.

• Links to climate

  Seasonal cycle linked to climate

  Salmonellosis in humans shows strong seasonal patterns in temperate regions, with summer peaks (June–September) closely tracking ambient temperature increases. Recent studies confirm a 3–5% rise in salmonellosis cases per 1°C temperature increase, driven by outdoor food-handling practices (e.g., barbecues) connected to accelerated bacterial replication in food matrices that are kept improperly during food preparation (35–37°C optimal growth range) In contrast, tropical regions show less seasonality due to stable warm temperatures over the year. Emerging data from neural network models indicate that humidity (>60%) and daylight duration (>12 hours) synergistically enhance transmission risks, particularly in coastal and urban areas.

  GAPS

  Lack of multi-year, cross-regional studies comparing seasonal drivers in temperate vs. tropical climates, particularly in low/middle-income countries with limited surveillance. There is a need to understand to which extent bad preparation/kitchen habits when barbecuing is explaining the increased number of human cases observed in summer. Additionally, there is a need for integrated frameworks combining meteorological data, genomic surveillance, and human mobility patterns to forecast outbreak timing and magnitude under climate change scenarios.

• Distribution of disease or vector linked to climate

  There are a large number of vectors and in warmer climates the activity of wild birds, rodents and flies may be greater, thus increasing the risk but generally there are no major climatic factors for the spread of the disease. Wild birds in North America/Europe show 30–50% higher Salmonella carriage rates during irruptive migrations linked to climate-driven food shortages. Fly populations in intensive farming systems increase 2.5× per 1°C temperature rise, mechanically transmitting Salmonella between livestock and crops. Floodwater mosquitoes (Aedes spp.) newly implicated in Salmonella dissemination during monsoon seasons in South Asia. Non-climatic factors (urbanization, intensive farming) interact with climate to reshape distributions. For example, Salmonella ST313 thrives in flood-prone slums with poor drainage.

  GAP

  Limited quantification of per-vector transmission efficiency How urban heat islands and agricultural irrigation patterns create microclimates favoring specific Salmonella-vector complexes. Role of microplastics and biofilms in aquatic systems as climate-resilient Salmonella reservoirs.

• Outbreaks linked to extreme weather

  Post-2020 studies demonstrating outbreaks to extreme weather: Floods: Hurricane Florence (2018) caused an 85% spike in Salmonella cases via groundwater contamination, with persistent environmental reservoirs detected over 6 months after the flood. Droughts: Water scarcity in the Horn of Africa (2023–2025) increased reliance on Salmonella-contaminated livestock reservoirs, driving a 40% case surge. Wildfires: Pyrogenic soils in fire-affected regions (e.g., Australia, California) show enhanced Salmonella survival via heat-induced sporulation-like states.

  GAPS

  Genomic tracking of storm-/fire-aerosolized Salmonella strains from environmental to clinical settings. Effectiveness of green engineering solutions (e.g., phage-treated retention ponds) in mitigating post-disaster transmission. Mechanisms enabling Salmonella persistence in low-moisture soils and xerophilic arthropods.

• Sensitivity of disease or vectors to the effects of global climate change (climate/environment/land use)

  Climate change affects Salmonella transmission through direct effects on pathogen biology and indirect impacts on vector/reservoir ecosystems. Elevated ambient temperatures accelerate bacterial replication rates (optimal growth: 35–37°C), while simultaneously extending the activity periods of arthropod vectors (e.g., flies, rodents) and amplifying their reproductive cycles. For instance, multidrug-resistant (MDR) Salmonella Kentucky strains now exhibit thermotolerance up to 42°C, enabling persistence in warming soils and livestock systems. Land-use changes compound these effects by altering microclimates and species interactions. Urban heat islands intensify local temperatures, fostering transmission in highly populated areas, while deforestation disrupts wildlife-livestock boundaries, introducing novel serovars like S. Llanos in the Amazon. Agricultural intensification further amplifies risks: irrigation with contaminated water and high-density farming create ideal conditions for biofilm formation on crops and equipment. These synergies are evident in recent outbreaks: Poultry farms in the U.S. Midwest reported a 40% rise in S. Enteritidis cases during prolonged heat waves (2023–2024), linked to accelerated bacterial growth in feed and fly-mediated spread Deforestation in Southeast Asia has increased human exposure to S. Weltevreden through encroachment into bat-inhabited forests.

  GAPS

  Spread in relation to vector population density and reproduction rate. How temperature/humidity gradients influence plasmid conjugation rates in environmental Salmonella populations. Impact of climate-driven urbanization on informal food systems (e.g., street vendors) as amplifiers of Salmonella diversity. Unintended consequences of climate-adaptive agriculture (e.g., wastewater irrigation) on Salmonella ecodynamics.

• Main perceived obstacles for effective prevention and control

  The widespread nature of the bacteria together with its longevity and diversity in the environment will be the main obstacles to prevention and control. It could be much more effectively controlled but the cost would be high in most cases. At the EU level, the situation is highly fragmented in terms of control and surveillance programmes implemented by different Member States, with the only exception being poultry flocks, for which national control programmes are applied in accordance with EU legislation.

  GAP

  Updated cost-benefit analyses related to control strategies that can be applied in different epidemiological contexts.

• Main perceived facilitators for effective prevention and control

  Improved farmers' awareness is necessary about the importance of implementing effective biosecurity measures to prevent the introduction and spread of a series of infections including Salmonella on their farms, especially because Salmonella infections usually have little or no impact on the animal, but may have relevant food safety implications for humans.

  Should more effective prevention and control be available, the surveillance regime in the EU may be scaled down thus saving several million Euro per year.

  GAP

  Design of a validation procedure for randomised testing to confirm continued high levels of control in the absence of a harmonised monitoring programme

Risk

• Salmonellosis in animals can lead to increased environmental contamination together with infected produce (eggs or meat) which can then cause outbreaks in the human population. Whilst these are generally self limiting they can occasionally lead to hospitalisation and ultimately to death. Epidemics have occurred in countries and have caused major reductions in the consumption of the offending produce thus risking the livelihood of the farmers as well. Salmonella can be transferred from meat to plant materials during food preparation so avoidance of meat may not rule out the risk of contracting the disease. There has been considerable build-up of resistance among the bacteria and therefore it is perceived to be a greater risk should the disease develop into one requiring hospitalisation.

  GAP:

  Relative risk and attribution resources and routes.Antimicrobial resistance gene transfer

Conclusion

• Conclusion summary (s)

  Salmonellae are widespread in the environment and they are generally most prevalent in areas of intensive animal husbandry. Many animals may be infected but show no clinical illness and are therefore important in relation to the spread of the disease. Although diagnostic methods are available, further developments leading to faster, more reliable, and affordable results would be valuable. Moreover, Salmonella typing is essential for many epidemiological investigations; however, it is currently performed—especially when based on whole genome sequencing (WGS)—in only a limited number of laboratories. At the EU level, the situation is highly fragmented in terms of control and surveillance programmes implemented by different countries with the exception of poultry populations. In most cases, Salmonella infection in livestock is asymptomatic, and pharmaceutical treatments are used only in rare situations—for example, to treat calves exhibiting clinical signs of infection. Effective control of Salmonella spp. relies fundamentally on the implementation of Good Farming Practices (GFP) and Good Hygienic Practices (GHP) along the entire food chain, from stable to table. The control approach involves the synergistic application of multiple interventions aimed at minimizing the risk of contamination. Control begins at the farm level and includes proper management practices combined with strict cleaning and disinfection protocols, pest control, and rigorous biosecurity measures. Additionally, Salmonella prevention can be supported by the use of feed or water additives such as prebiotics, probiotics, competitive exclusion agents, and organic acids. Equally important is maintaining high standards of slaughter hygiene to prevent meat contamination. Vaccines are available, but better and more effective products may be available. Additionally, more information is required on the optimal use of vaccines within control programmes, as well as on the cost-benefit analysis of vaccination in different epidemiological contexts.

Sources of information

• Expert group composition

  Francesca Martelli: Animal and Plant Health Agency, Addlestone, United Kingdom

  Laetitia Bonifait: ANSES, French agency for food, environmental and occupational health Safety, Ploufragan France

  Marianne Chemaly: ANSES, French agency for food, environmental and occupational health Safety, Ploufragan France

  Istvan Szabo: German Federal Institute for Risk Assessment (BfR), Berlin Germany

  Lis Alban: Danish Agriculture and Food Council / University of Copenhagen Denmark

  Pietro Antonelli: Italian National Reference Laboratory for Salmonella Italy

  Laura Bortolami: Italian National Reference Laboratory for Salmonella Italy

  Lisa Barco: Italian National Reference Laboratory for Salmonella Italy

• Reviewed by

  Project Management Board.

• Date of submission by expert group

  30th June 2025

• References

  This analysis is based on expert insights and, in some instances, supported by selected references. However, some information may reflect expert opinions, which could influence interpretations. Readers are encouraged to seek additional sources if they require specific details.

  Recommended Citation

  "Martelli F., Bonifait L., Chemaly M.,Szabo I.,Alban L.,Antonelli P.,Bortolami L.,Barco L., 2025. DISCONTOOLS chapter on Salmonellosis https://www.discontools.eu/database/51-salmonellosis.html"

  Online references

  http://www.oie.int/eng/normes/mcode/en_chapitre_1.6.5.htm#rubrique_Salmonella_Typhimurium_chez_les_volailles

  http://www.apd.rdg.ac.uk/AgEcon/livestockdisease/poultry/poultrysalm3.html

  http://www.safe-poultry.com/documents/2006-1177%20EC%20.pdf

  http://www.safe-poultry.com/documents/2006-1168%20EC.pdf

  http://www.apd.rdg.ac.uk/AgEcon/livestockdisease/cattle/salmon.htm

  http://www.oie.int/eng/normes/mmanual/A_00129.htm

  http://www.cdc.gov/nczved/dfbmd/disease_listing/salmonellosis_gi.html

  http://lib.bioinfo.pl/meid:10775

  http://www.reading.ac.uk/foodlaw/news/eu-06132.htm

  http://www.biomedcentral.com/1746-6148/1/2

  http://www.actavetscand.com/content/49/1/35

  http://www.efsa.eu : annual zoonosis report and report on Salmonella on livestock

  https://www.animalshealth.es/fileuploads/user/PDF/2023/10/guideline-quality-Guia-EMA-bacteriofagos-veterinaria.pdf.

  https://efsa.onlinelibrary.wiley.com/doi/epdf/10.2903/j.efsa.2024.9106

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