Diseases

Porcine cysticercosis

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Control Tools

  • Diagnostics availability

  • Commercial diagnostic kits available worldwide

    One cysticercosis Ag ELISA (human, pig). A number of assays for antibodies to T. solium in humans are now available commercially. These use ELISA or western blot technology.

    GAPS :

    • Lack of diagnostic tests for porcine cysticercosis (and human taeniosis) that have a validated high performance.
    • Serum bank needed with well documented serum to study sensitivity, specificity, reproducibility of serological tests.
    • Need for proper test validation in different geographical areas, for their specific use at different levels.
  • Commercial diagnostic kits available in Europe

    One cysticercosis Ag ELISA (human, pig). A number of assays for antibodies to T. solium in humans are now available commercially. These use ELISA or western blot technology.

    GAP :

    There is limited production thus affecting distribution and availability in Africa, Latin America and Asia.

  • Diagnostic kits validated by International, European or National Standards

    None.

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

    Methods are described in the OIE Manual of Diagnostic Tests and Vaccines for Terrestrial Animals 2019 Chapter 3.9.5. – (5) Cysticercosis. These include:1. Identification of the agent ;2. Serological tests (Ag and Ab detection) ;3. Molecular confirmation.WHO FAO OIE guidelines for surveillance and prevention and control of taeniosis/cysticercosis (2005): chapter 4, pp 45-56 (6).

  • Commercial potential for diagnostic kits in Europe

    Yes. The commercial potential is there for human cysticercosis, not for porcine cysticercosis.

  • DIVA tests required and/or available

    None available.

    GAP :

    Current immunological tests for diagnosis are insufficiently specific to form the basis for their evaluation in relation to differentiation of responses to infection versus vaccination.

  • Opportunities for new developments

    Development of a diagnostic test that has a high positive and negative predictive value and, particularly, a lack of cross-reactivity with T. hydatigena.Development of high performing, field applicable tests (TPPs).

    GAP :

    See Section “Main means of prevention, detection and control – Diagnostic tools”.

  • Vaccines availability

  • Commercial vaccines availability (globally)

    Cysvax® available from Indian Immunologicals Limited, Hyderabad, India.

    GAP :

    Registration and availability in more endemic countries.

  • Commercial vaccines authorised in Europe

    No.

  • Marker vaccines available worldwide

    No.

  • Marker vaccines authorised in Europe

    No.

  • Effectiveness of vaccines / Main shortcomings of current vaccines

    To date field trials of this combined strategy (human treatment, pig treatment ad vaccination, education) have been 100% effective in eliminating viable infection with T. solium.Vaccination with Cysvax®, or the TSOL18 on which the vaccine is based, together with oxfendazole medication of pigs, has been evaluated in field trials undertaken in Cameroon, Peru, Nepal, Tanzania, Zambia and Uganda. To date 71,012 pigs have been vaccinated, 698 vaccinated pigs have been assessed by necropsy (187 half carcass, 511 full carcass) up to 12 months after vaccination. No vaccinated pig has been found to harbour a viable T. solium cyst.The main shortcoming of Cysvax® is the requirement to give two immunizations. Cysvax® is not believed to clear cysts already present at the time of vaccination (hence the recommendation to combine vaccination with oxfendazole medication).

    GAP :

    See Section “Main means of prevention, detection and control – Vaccines”.

  • Commercial potential for vaccines in Europe

    None in Europe.The importance of cysticercosis due to T. solium in humans increases the costs of the disease, but it remains to be seen whether the significance of the disease in endemic countries will be sufficient to push commercial production of the vaccine for use in pigs to prevent cysticercosis and to break the chain.

  • Regulatory and/or policy challenges to approval

    Challenges with cost and maintenance of registration.Lack of interest/commitment on policy level.

    GAPS :

    • Advocacy.
    • Policy analyses.
  • Commercial feasibility (e.g manufacturing)

    Feasible to manufacture but will depend on the demand and potential markets. This in turn will be linked to cost especially for the developing countries. Lack of commercial incentives for use of cysticercosis vaccine by poor farmers.As the disease is considered a neglected tropical disease affecting resource poor farmers, governments need to be convinced to adopt vaccination and treatment as a control measure.

    GAPS :

    • Lack of recognition of porcine cysticercosis by policy makers as an important disease of great public health and economic importance.
    • Need for more accurate burden data.
    • Combination with commercially valuable porcine vaccine (production limiting disease) to improve vaccine uptake.
  • Opportunity for barrier protection

    Limited but could be used in a region or zone as part of a control programme.

  • Opportunity for new developments

    GAPS :

    • Combination with commercially valuable porcine vaccine(s).
    • Develop one dose vaccine.
    • Formulation that would not require refrigeration.
    • Oral formulation.
  • Pharmaceutical availability

  • Current therapy (curative and preventive)

    Oxfendazole (30mg/kg) is effective to kill cysticerci in pigs (not in the brain) but withdrawal times need to be adhered to (21 days). Oxfendazole also impacts on other gastro-intestinal helminths.Registered for pigs in India for PCC (ongoing in SA).

    GAPS :

    • Traceability systems need supporting to limit treated pigs entering food chain before withdrawal time.
    • Improved capacity for regulatory enforcement to encourage uptake of vaccine/anthelmintic and adherence to withdrawal times.
    • Anthelmintic resistance in pigs needs monitoring if uptake of oxfendazole is encouraged.
  • Future therapy

    GAPS :

    • Formulation that would not require refrigeration.
    • In vitro techniques for drug screening.
    • Studies on possible (phyto)medicines for local treatment of porcine cysticercosis.
  • Commercial potential for pharmaceuticals in Europe

    None.

  • Regulatory and/or policy challenges to approval

    Challenges with cost and maintenance of registration.Lack of interest/commitment on policy level.

    GAPS :

    • Advocacy.
    • Policy analyses.
  • Commercial feasibility (e.g manufacturing)

    Oxfendazole currently available as a GMP-manufactured product registered for use in pigs for cysticercosis (in India).

    GAPS :

    • Cost-benefit/gross margin analysis for uptake of oxfendazole by pig farmers needed.
    • Appropriate pack sizes and price point needed.
    • Lack of registration for use in pigs in many endemic countries.
  • Opportunities for new developments

    GAPS :

    • Formulation.
    • Studies on possible (phyto)medicines for local treatment of porcine cysticercosis.
  • New developments for diagnostic tests

  • Requirements for diagnostics development

    Published Target Product Profiles already developed by the WHO and published.

  • Time to develop new or improved diagnostics

    From development through validation to commercial availability will be time consuming (5 to 10 years).

  • Cost of developing new or improved diagnostics and their validation

    The development of an improved diagnostic test is expensive. It is questionable if a potential market is available.

    GAPS :

    • Funding.
    • Interest of policy makers (governments, International/regional and National health and food safety agencies), funding organisations, ngo’s and other stakeholders.
  • Research requirements for new or improved diagnostics

    GAP :

    See above(for human: test that detects cysticerci only outside the brain).

  • Technology to determine virus freedom in animals

    Not applicable.

  • New developments for vaccines

  • Requirements for vaccines development / main characteristics for improved vaccines

    Currently available evidence indicates that Cysvax® is almost 100% effective and protection is maintained for the lifespan of most pigs. A vaccine which simultaneously eliminated pre-existing infection would be an improvement, but the costs of scale-up and registration would be unlikely to be borne by any company considering the effectiveness of the existing vaccination and medication approach.Single-shot vaccine.Combination of Cysvax® with other commercially valuable porcine vaccines used or needed in T. solium endemic countries, particularly African Swine Fever, if an effective vaccine were ever developed commercially.

  • Time to develop new or improved vaccines

    10+ years.

  • Cost of developing new or improved vaccines and their validation

    High.

  • Research requirements for new or improved vaccines

    A single shot vaccine might be achieved by pulse-release vaccine formulations or by live recombinant vaccine bacterial or viral vectors which may give a long-lasting immunity after one immunisation.

    GAP :

    Protection level when a combined vaccine is administered.

  • New developments for pharmaceuticals

  • Time to develop new or improved pharmaceuticals

    Time to develop would depend on the product and the trials necessary to validate the efficacy and safety. Commercial production would then take further time.

  • Cost of developing new or improved pharmaceuticals and their validation

    Costly. With oxfendazole already on the market it is unlikely that big pharmaceutical companies will endeavour into the costly development of new products.

  • Research requirements for new or improved pharmaceuticals

    • Formulation.
    • Studies on possible (phyto)medicines for local treatment of porcine cysticercosis.
    • Market studies including willingness to pay.
    • Uptake in local veterinary systems.
    • Distribution and delivery studies.
    • Storage conditions (refrigerated conditions).
    • Cost-effectiveness studies.
    • Formulation (feed based or oral).
    • Studies on possible phytomedicines/alternatives for local treatment of porcine cysticercosis.

Disease details

  • Description and characteristics

  • Pathogen

    Porcine cysticercosis occurs when pigs become infected with the larval (metacestode) stages of Taenia solium after ingestion of its eggs. Humans are the definitive host of the tapeworm, which causes taeniosis. Humans may also act as accidental intermediate hosts and develop human cysticercosis.

  • Variability of the disease

    The cysticerci of the human tapeworm T. solium cause porcine cysticercosis and occur mainly in muscles and the central nervous system, though the liver and other organs of the pig may also be infected.There may be single or multiple metacestode larval infections in humans and pigs.An Asian and an Afro/American genotype of T. solium have been described.The adult stages of T. solium occur in the intestine of humans. Usually only one adult worm is observed, though there are numerous reports of multiple worms in one individual.

    GAPS :

    • Importance of strain differences
    • Alternative hosts (wildlife, dogs)
  • Stability of the agent/pathogen in the environment

    The tapeworm’s eggs are shed into the intestine within a proglottid and subsequently may spill out into the intestinal contents. The eggs remain in the faecal bolus and when excreted may be disseminated by rain, wind and invertebrates, contaminating soil, vegetation and water. T. solium eggs are immediately infective for both pigs and humans following release from the tapeworm and can survive in the environment for months.

    GAP :

    • Presence, density, distribution, persistence, viability and infectivity of the eggs in different environmental conditions (including climatic conditions, land conditions, anthropogenic activities) and different matrices (e.g., soil, water, vegetables).
  • Species involved

  • Animal infected/carrier/disease

    Porcine cysticercosis may be caused by the larval stages of the parasitic cestodes T. solium, Taenia hydatigena and Taenia asiatica. Only T. solium causes cysticercosis in the muscle or central nervous system of pigs.

    GAP :

    Possible involvement of dogs, wild pigs, warthogs, non-human primates.

  • Human infected/disease

    Human cysticercosis occurs by accidental ingestion of T. solium tapeworm eggs, via human-to-human transmission or auto infection (when eggs released by a tapeworm hatch in the stomach of the same host, provoking cysticercosis in the host harbouring the adult worm). Infection occurs when an oncosphere enters the body and forms a cysticercus, which may establish in the muscles, subcutaneously, in the eyes and in the central nervous system, leading to the most serious form, neurocysticercosis.Human taeniosis occurs after consumption of undercooked pork infected with viable cysticerci, whereafter a tapeworm may establish in the human intestines.

  • Vector cyclical/non-cyclical

    Mechanical vectors only, whereby insects have been shown experimentally to have the potential to carry taeniid eggs.

    GAPS :

    • Role and importance of insects (e.g. dung beetles, flies) in the dispersion.
    • Tracing of dispersion of faecal contamination.
  • Reservoir (animal, environment)

    Only humans, pigs.Dogs have been shown to develop naturally acquired infections with viable cysticerci. In areas where dogs are eaten, they pose a potential risk for transmission if the meat is eaten raw or inadequately cooked.Environmental reservoir/contamination, see 1.3.

    GAPS :

    • Gaps for environmental contamination: See Section “Stability of the agent/pathogen in the environment” and to define geospatial determinants of egg distribution, persistence, and infectivity in endemic areas.
    • Presence, role, and importance of other reservoirs, such as wild pigs, warthogs, especially in interface areas.
  • Description of infection & disease in natural hosts

  • Transmissibility

    Human-to-pig transmission when pigs ingest eggs shed by tapeworm carriers (see above), leading to porcine cysticercosis.Pig-to-human transmission via consumption of undercooked pork infected with viable cysticerci, leading to human taeniosis.Human-to-human transmission (ingestion of eggs from a tapeworm carrier, mechanical via contaminated food/water, auto-infection), leading to human cysticercosis.

    GAPS :

    • Routes of infection and their relative importance, e.g. foodborne transmission of eggs (e.g., via poor hand hygiene) versus waterborne transmission of eggs, human autoinfection, role of vectors… .
    • The role of pig-to-pig transmission via contaminated faeces, the role of pigs as transport hosts.
    • The role of environmental conditions in the transmission of T. solium eggs (see also Section “Stability of the agent/pathogen in the environment”).
    • Investigate whether true intestinal autoinfection is possible and taking place or whether autoinfection is a result of the faecal-oral route only.
  • Pathogenic life cycle stages

    Parasite eggs are shed from humans infected with the adult tapeworm, ingested by pigs, after which the oncospheres penetrate the intestine and migrate to muscle tissue, and the brain and develop into cysticerci. The parasite life cycle is completed when humans ingest undercooked pork containing viable cysticerci. Cysticerci evaginate and attach to the small intestine by their scolex resulting in human tapeworm infection.

    GAPS :

    • Impact environmental conditions on persistence, dispersal, and infectivity of eggs (see also Section “Stability of the agent/pathogen in the environment”).
    • Role and importance of invertebrates in dispersal(see also Section “Species involved – Vectors cyclical/non-cyclical).
  • Signs/Morbidity

    Usually asymptomatic, although seizures can occur and have been observed. Like in humans, the type and severity of the clinical signs depend on the number and location of the larvae. Heavy infections can result in severe seizures.

    GAP :

    Further details on pathogenesis of porcine cysticercosis and clinical symptoms, including factors that trigger seizures. These could be helpful to better understand the natural history of central nervous system infections in human.

  • Incubation period

    Cysticerci may be visible by 6 weeks and fully developed between 60 to 70 days after infection.

    GAPS :

    • Factors influencing establishment of infection.
    • Influence of prior exposure and maternal antibodies on establishment of infection.
    • Proportion of transient infections, of oncospheres passing the intestinal wall, and developing into cysticerci.
    • Optimisation of experimental infections.
  • Mortality

    No data, appears to be minimal.

  • Shedding kinetic patterns

    Adult tapeworms which develop in humans may reside in the small intestine for months/years. Multiple proglottids may be released each day after the worm has matured, commonly as many as 5 segments per day per worm, each with tens of thousands of eggs which are immediately infective to pigs and humans when passed.

    GAPS :

    • Proportion of infective eggs of the total number excreted.
    • Tapeworm lifespan.
  • Mechanism of pathogenicity

    Development of cysticerci in different tissues in pigs and humans. Collagen deposition in the pig brain tissue, showing as large fibrotic scars and moderate amount of collagen deposited around cysts. Only viable cysticerci remain infective.

    GAP :

    Immunological responses to the cysticerci in the pig brain (cellular versus humoral) (as a model for human infection).

  • Zoonotic potential

  • Reported incidence in humans

    Worldwide, taeniasis and cysticercosis are common parasitic infections in areas where pigs roam freely and can come in contact with human faeces harbouring parasite eggs, mostly due to poor sanitation and where meat inspection is not (sufficiently) performed. Cysticercosis and taeniosis are rare in the U.S. and most parts of Europe.

    GAPS :

    • Estimations of incidence of taeniosis and (neuro)cysticercosis in different settings/areas.
    • Monitoring of/ obtain data on active transmission in different settings, including non-endemic areas.
  • Risk of occurence in humans, populations at risk, specific risk factors

    Risk has been related with (free ranging) pigs, lack of meat inspection, consumption of undercooked meat, poor sanitation/personal hygiene, environmental faecalizationand lack of knowledge.Specifically, for taeniosis: consumption of undercooked meat (culinary habits), lack of meat inspection, bad practices related to infected meat (improper disposal, lack of freezing, lack of heating).For cysticercosis: living in a household with a tapeworm carrier (close contacts), poor sanitation and poor personal hygiene. If there is a human excreting T. solium eggs in the environment, human cysticercosis can occur in local population even though pork is not eaten, and the environment is not shared with pigs.

    GAPS :

    Neurocysticercosis:

    • Relative risk for human neurocysticercosis of tapeworm carriers and their close contacts versus environmental exposure.
    • Human susceptibility and immunity to T. solium taeniosis/cysticercosis, including after prior exposure.

    Taeniosis:

    • Source of infection, more specifically the risk of occurrence in human based on cysticerci burden in pig.
  • Symptoms described in humans

    Human cysticercosis often becomes symptomatic only when cysticerci are developing, degenerating, dying or becoming large enough to interfere with the blood flow. Cysticerci in the muscles do not generally cause symptoms. Sub-cutaneous nodules in humans are common in parts of Latin America and Asia. Although rare, in the eyes cysticerci may cause blurry or disturbed vision and may also cause swelling or detachment of the retina. Symptoms of neurocysticercosis depend upon the number, stage and localisation of cysticerci found in the central nervous system. Epileptic seizures and severe progressive chronic headaches are the most common symptoms. Confusion, lack of attention to people and surroundings, difficulty with balance, hydrocephalus may also occur. Death can occur suddenly with heavy infections or in case of low infections when hydrocephalus is created.T. solium taeniosis is usually asymptomatic; though rare cases of abdominal complaints, nausea, weight loss, diarrhoea, constipation have been described.

    GAPS :

    • Importance (including occurrence, proportion/distribution, attribution, burden) of neurocysticercosis related symptoms such as seizures, severe progressive chronic headache, cognition, stroke, dementia, haematological brain disease, psychiatric problem, vision loss and mortality rates, require more research in different settings (clinical and population/community).
    • Variation in manifestations and reasons for this variation (host or parasite related, genetic variations, geographic variations).
    • Timing and duration of symptoms after infection (including proportion of infected people remaining asymptomatic).
    • Proportion of symptomatic taeniosis cases.
  • Estimated level of under-reporting in humans

    High. This is classified as a neglected zoonosis. Neurocysticercosis (and taeniosis) is not a notifiable disease in most countries. Neurocysticercosis requires imaging for diagnosis which leads to an underestimation in areas where such facilities are lacking or less accessible due to the high cost.

    GAPS :

    • Underdiagnosis and underreporting is a major gap.
    • The real prevalence and incidence of taeniosis, cysticercosis and in particular neurocysticercosis need to be assessed in different areas.
    • Regional mapping and co-endemicity with other Neglected Tropical Diseases.
  • Likelihood of spread in humans

    T. solium eggs spread from human-to-human, through contaminated food and drinking water or by direct contact with infected faecal material.See also Section “Zoonotic Potential - Risk of occurrence in humans, populations at risk, specific risk factors”.

    GAPS :

    • Consolidation of transmission dynamics models, inclusion of neurocysticercosis component, economic component to guide interventions.
    • Define the relative transmission via foodborne versus waterborne versus autoinfection, importance of transmission via invertebrates, fomites.
    • Duration of infection with adult T. solium in humans (see also Section “Description of infection & disease in natural hosts – shedding kinetic patterns).
    • Define factors that lead to (lack of) further development of the immature worm into adults, after consumption of viable cyst(s)
  • Impact on animal welfare and biodiversity

  • Both disease and prevention/control measures related

    There is evidence of epileptic fits in infected pigs, indicating a previously under-acknowledged animal welfare issue. Porcine neurocysticercosis might have a negative impact on welfare due to altered behaviour patterns in pigs (including less time spent on feeding, more passive behaviour and decreased social interaction). Confinement of the pigs is recommended for control of this parasite, to avoid pigs having access to human stool whilst this can reduce some welfare issues (tether wounds, potential harm to free-ranging pigs) there is a potential for detrimental welfare outcomes when insufficient consideration is given to housing design, environmental enhancement, water and feed provision.

    GAPS :

    • Economic evaluation of pig confinement, assessing cost benefits to the farmer and societal level including welfare outcomes and impact on other pig diseases.
    • Development of appropriate animal-welfare education tools for resource-limited areas (build on work undertaken by welfare NGOs).
    • Pig spatial ecology studies with movement detection to verify clinical signs in pigs.
    • Impact of treatment of pigs on other helminth infections and productivity.
  • Endangered wild species affected or not (estimation for Europe / worldwide)

    No.

  • Slaughter necessity according to EU rules or other regions

    No.

  • Geographical distribution and spread

  • Current occurence/distribution

    T. solium is found principally in resource poor areas of Latin America, sub-Saharan Africa, non-Islamic countries of Asia, including India and China, where there are free ranging, scavenging pigs and where sanitation is poor or lacking and meat inspection is not or poorly performed.

    GAPS :

    • More studies required to delineate areas of prevalence.
    • Development of risk maps.
  • Epizootic/endemic- if epidemic frequency of outbreaks

    Endemic; unlikely to occur as an epidemic, but clusters of infection have been reported in regions where the full life cycle does not occur.

  • Seasonality

    Possibly in pigs where the infection is linked to the period of harvesting – pigs that are housed or tethered in the crop growing season are allowed to roam after harvesting.

    GAP :

    See also Section “Stability of the agent/pathogen in the environment”.

  • Speed of spatial spread during an outbreak

    Important in a post elimination phase: Depends on the number of tapeworm carriers (humans), level of hygiene and sanitation, the contamination of the environment and presence of free roaming pigs, or pigs with access to human stool.

    GAPS :

    • Movement of pigs within villages and between villages.
    • Impact of human mobility.
  • Transboundary potential of the disease

    Spread by people (human-to-pig or human-to-human) and infected pork sold across borders (pig-to-human).

    GAP :

    Monitoring and surveillance systems.

  • Route of Transmission

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

    For porcine cysticercosis: Pigs acquire infection from ingestion of segments and eggs contained in human faeces that may also contaminate herbage, water, vegetation etc.

    GAPS :

    • Studies on environmental contamination.
    • Role and relative importance of different transmission routes (via ingestion of stool, ingestion contaminated feed/water, contaminated environment, insects, pig-to-pig…).
  • Occasional mode of transmission

    For porcine cysticercosis: Insects have been shown experimentally to have the potential to transport taeniid eggs (dung beetles with T. solium and T. saginata; flies with T. hydatigena).

    GAPS :

    • Presence, role, and importance of other reservoirs, such as wild pigs, warthogs, especially in interface areas.
    • Importance of pig-to-pig transmission via faeces.
    • Investigate dog-to-pig transmission via faeces.
  • Conditions that favour spread

    Free roaming pigs. Lack of meat inspection, lack of knowledge. Consumption of undercooked meat. Clinically normal humans infected with T. solium excreting high levels of tapeworm eggs in their faeces. Poor sanitation and hygiene.

    GAP :

    • Studies on environmental contamination.
  • Detection and Immune response to infection

  • Mechanism of host response

    Humoral, cellular, and non-specific host responses to cysticerci. High levels of protective immunity are induced by immunization of pigs with antigens in oncospheral extracts. It is considered that immunity in pigs is largely antibody mediated as evidenced by passive and maternal transfer of immunity which occurs in hosts of related taeniid species (not shown for T. solium specifically).

    GAPS :

    • Effectiveness and longevity of immune responses after infection.
    • Transfer of maternal antibodies to piglets, effectiveness, and duration of protection.
    • Age related development of immune response in piglets born to infected/non infected mothers.
    • Herd immunity created by exposure: impact of control measures.
    • Cross protection with T. hydatigena.
  • Immunological basis of diagnosis

    In pigs: Antibody and antigen detection. All existing serological tests show (high) levels of cross-reactivity (with T. hydatigena and other infections).

    GAP :

    Development and evaluation of highly specific and sensitive serological tests for T. solium, adapted to the place of use.

  • Main means of prevention, detection and control

  • Sanitary measures

    Contact between pigs and human stool or feed, water, environment contaminated with infected human stool needs to be prevented. Housing of pigs may play an important role, whereby safe feed and water should be provided. Sanitation (use of toilet, hand washing) and specific sanitation practices should be implemented for the disposal of human stool after treatment. Food hygiene practices should be applied.The effectiveness of these measures is strongly linked to uptake and compliance of the good practises.

    GAPS :

    • Conduct implementation hybrid studies (implementation and effectiveness) to identify specific barriers and opportunities and propose solutions for implementation of sanitation measures ensuring uptake and sustainability; and to define cost effectiveness.
    • Egg persistence in night soil, in different sewage/wastewater management systems.
    • Understanding of traditional taboos that lead to lack of use of sanitary facilities in endemic regions.
    • Stronger partnerships with WASH actors needed including ethnographic studies to improve uptake of WASH interventions.
  • Mechanical and biological control

    NA.

  • Diagnostic tools

    Diagnosis in animals is usually based on the detection of the cysticerci at meat inspection (low sensitivity) or necropsy. In many endemic countries farmers and pig traders look at the tongue to detect cysts or cut external masseters for cyst detection (ante mortem). Light infections are often missed. Tests for antibodies or antigens in serum are not used currently for the diagnosis of cysticercosis in pigs except for research purposes. The existing tests show limitations in sensitivity and specificity.Full carcass dissection is the current gold standard, though only used for research purposes.Target Product Profiles (TPPs) have been developed, including TPPs for porcine cysticercosis.

    GAPS :

    • Improved diagnostic tools needed in pigs, for ante- and/or post-mortem use.
    • Serum bank needed with well documented serum to study sensitivity, specificity, reproducibility of serological tests.
    • Improved diagnostics to study environmental contamination and infectivity of eggs.
    • Improved diagnostics for the detection of taeniosis.
    • Building on the target product profiles, define at which level in the food chain (pigs/pork)/ health system (human) to detect and for which purpose (screening, monitoring, food safety), as well as the most suitable test formats (POC, high throughput…).
  • Vaccines

    Cysvax® is the only commercially available, registered vaccine for porcine cysticercosis. It is manufactured under Good Manufacturing Practice conditions by Indian Immunologicals Limited in Hyderabad, India. The vaccine incorporates the recombinant TSOL18 oncosphere antigen expressed by Pichia pastoris. The vaccine has been shown to be safe and effective in field trials that were undertaken in Cameroon, Peru Nepal, Tanzania, Zambia, and Uganda. The vaccine is registered in India and Bhutan, with registration dossiers submitted in several countries in East and Southern Africa and South-East Asia.

    Cysvax® is not believed to have any impact on cysticerci that may be in the muscles of pigs at the time they are vaccinated. For this reason, the vaccine is recommended to be given together with an oral medication (30mg/kg) with oxfendazole which will eliminate any cysticerci that may have established in the muscles prior to full vaccination. Two doses are needed to obtain maximum protection.

    Other vaccine candidates have been developed/ are under development but have been less extensively tested and are currently not commercialised nor registered.

    GAPS :

    • Uptake in local veterinary systems.
    • Market studies including willingness to pay.
    • Distribution and delivery studies.
    • Combination with other vaccines (e.g., classical swine fever, African swine fever if developed).
    • Studies on the duration of immunity, impact of transfer of maternal antibodies, number of needed vaccine doses (single dose option) and vaccination schedule (age groups), etc with Cysvax® and others when available.
    • Storage conditions (refrigerated conditions).
    • Cost-effectiveness studies (including incremental cost of vaccine over oxfendazole alone).
    • Formulation: Oral vaccine.
  • Therapeutics

    30mg/kg oxfendazole kills 100% muscle cysts within 4 weeks of dosing; it does not kill brain cysts. Dead cysts leave lesions for as long as 6.5 months after treatment; a large number of such lesions could potentially make a carcase inedible. Cysticerci are degenerated (and no longer infectious) within one week after treatment. Drug residues in the meat of treated pigs require the animals to be withheld from slaughter for human consumption for 21 days. A single manufacturer of oxfendazole has the drug available as a product registered for use against porcine cysticercosis (Oxfenvet). Manufacturing, and registration of the product has recently been transferred from MCI Santé Animale in Morocco to Indian Immunologicals Limited in India.

    (For taeniosis: Treat humans against tapeworms and introduce sanitation for the disposal of human faeces.).

    GAPS :

    • Market studies including willingness to pay.
    • Uptake in local veterinary systems.
    • Distribution and delivery studies.
    • Storage conditions (refrigerated conditions).
    • Cost-effectiveness studies.
    • Formulation (feed based or oral).
    • Studies on possible phytomedicines/alternatives for local treatment of porcine cysticercosis.
  • Biosecurity measures effective as a preventive measure

    No contact of pigs with infected human stool or contaminated feed/water. Enclose pigs, no feeding with human stool.

    GAPS :

    • Implementation studies (uptake and sustainability) Acceptability and socio-economic impact of any biosecurity measures.
    • Investigate the added value of increased biosecurity for other pathogens using a systems approach.
    • Investigate the need for insect control in housing systems.
  • Border/trade/movement control sufficient for control

    Legislation regarding border control is available and is (more or less) implemented. Whether pigs originating from endemic areas (mostly rural settings) are transported across (regional) borders, is unknown but assumed less likely.

    GAPS :

    • Insufficient information exists regarding cross-border trade, movement of pigs and introduction of T. solium infection via human mobility in the current endemic areas.
    • Implementation/enforcement of measures that could be implemented as effective border controls (need for incentives, motivation, improved diagnostic tools).
    • Trade implications of future vaccination programs.
    • Design, implementation and enforcement of monitoring and surveillance systems, tracing systems, movement control.
  • Prevention tools

    Porcine cysticercosis can be decreased by preventing or treating T. solium taeniosis in humans combined with good sanitation and hygiene. Pigs should not be exposed to human faeces, or food and water contaminated with tapeworm eggs.Pigs should be housed.Pork should be inspected before entering the food chain and/or properly cooked. Improved knowledge about the disease in affected communities is needed.Prevent humans from eating uncooked or poorly cooked tissues of infected pigs.Prevention of illegal slaughter and selling of uninspected, infected pork.Enhanced meat inspection removes infected pork from being consumed.

    GAPS :

    • Hybrid implementations studies with a cost effectiveness component.
    • Production of tools fit for different settings and target groups.
    • Community engagement methods.
    • Inclusion in existing programmes in health and veterinary sectors.
    • Regular impact assessments.
    • Ensure impact on behaviour change.
  • Surveillance

    Routinely through meat inspection in abattoirs. Meat inspection has a low sensitivity, a lot of especially lightly infected carcasses will be missed. Nevertheless, large numbers of pigs are home slaughtered or in illegal slaughter places where carcases are not controlled.

    GAPS :

    • Design and implementation of monitoring and surveillance systems, including an enforcement of adequate surveillance throughout the food-chain (e.g., at butcher shops).
    • Cheap and easy-to-use sensitive and specific, evaluated and validated diagnostic tests for pigs (ante- and post-mortem).
    • Serological tests need to be evaluated for use in epidemiological studies.
    • For neurocysticercosis: Rendering neurocysticercosis a notifiable disease.
  • Past experiences on success (and failures) of prevention, control, eradication in regions outside Europe

    Sustainable success in control requires an integrated One Health approach utilizing two or more control options targeting both the intermediate (pig) and definitive host (human).Numerous trials have evaluated the impact of health education and/or treatment of humans with taeniacides, and/or vaccination plus medication of pigs on T. solium transmission, with varying frequencies and design (mass treatment/ vaccination, targeted, ring based etc) with varying outcomes, measured over relative short intervals of time. Trials focussing on one host generally have a more modest reduction in transmission.An optimal health education strategy was designed using the PRECEDE-PROCEED (Predisposing, Reinforcing, and Enabling Constructs in Educational Diagnosis and Evaluation) model in Burkina Faso. Results showed a small though significant decrease in cumulative incidence and prevalence of active human cysticercosis in two of the three provinces included in the study.Two studies (Peru and Zambia) have evaluated frequent Cysvax® vaccination plus oxfendazole treatment of pigs together with treatment of the human population with taeniacide and health education in school going children (Zambia) and the general population. Both studies achieved the elimination of active T. solium transmission in pigs.Studies in Tanzania and Uganda, combining pig vaccination and treatment have also obtained significant reductions in porcine cysticercosis. In Lao PDR the combination of human and porcine mass drug administrations as well as porcine vaccination led to a significant decrease in human taeniosis.

    GAPS :

    • Hybrid implementation studies of proven effective, existing control strategies including cost-effectiveness assessments, considering finance mechanisms across sectors following an integrated One Health based control.
    • Development of practical and sustainable strategies for the implementation of pig vaccination and medication.
    • Evaluation of the rate at which transmission is reintroduced after implementation of a disease elimination strategy.
    • Identification of suitable measures to sustain a zero or low level of disease following implementation of a disease elimination/control strategy.
    • Define clear targets and how and where these should be measured (which diagnostic tools).
    • Design and set up of monitoring and surveillance systems.
    • Policy analyses.
    • Advocacy for policy uptake and change.
    • Long term follow up of control implementation.
    • Capacity development within veterinary public health (meat hygiene) and work on mechanisms to improve enforcement of legislation.
    • Condemnation of infected pigs and loosing informal market loopholes will provide disincentive for presenting infected pigs to slaughter (stimulating willingness to pay for vaccine).
    • System dynamics modelling required to understand wider impacts of control options.
  • Costs of above measures

    Insufficient cost data available, potentially high relative costs for low-income countries.One study in Lao PDR indicated the need to include impact on other pathogens benefiting from the control strategies (e.g., soil transmitted helminths in human) to improve the cost effectiveness of the intervention.

    GAPS :

    • Lack of costing data, especially from implementation studies.
    • Need for (incremental)cost-effectiveness and cost-benefit assessments of different combinations of control options.
    • Need for studies taking the One Health approach into account in cost-effectiveness and cost-benefit analyses.
    • Explicit consideration of cost-sharing scenarios (health/veterinary + public/private).
    • Cost-benefit/gross margin from farmer’s perspective needed for farm-based interventions as well as a wider exploration of combined farm interventions.
  • Disease information from the OIE

  • Disease notifiable to the OIE

    No.

  • OIE disease card available

    No.

  • Socio-economic impact

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

    The WHO/FERG initiative estimated the global burden of T. solium at 2.79 million DALYs/year, causing over 28 thousand deaths per year (2010 estimate). Including symptomatic and asymptomatic cases, the total number of people with neurocysticercosis, has been estimated between 2.56–8.30 million. Due to its significant socio-and economic burden it was ranked as most important foodborne parasite by WHO and FAO.Country level estimates of human health and economic burden have been published for Cameroon, Tanzania, Mozambique, Ecuador, India, Mexico and South Africa.The Value of Statistical life approach used to combine human health and economic losses in pig industry into single monetary burden for; Burkina Faso, Egypt, Ethiopia, Nigeria, Uganda.

    GAPS :

    • Only neurocysticercosis -associated epilepsy has been included in the burden estimates so far. Data on the prevalence / incidence of neurocysticercosis and the distribution of symptoms is not known enough to obtain a fair estimate of DALYs (which are highly underestimated).
    • Improved mortality data.
    • Monetary burden of neurocysticercosis in different areas.
    • Stigma associated with neurocysticercosis in different areas.
    • Productivity losses associated with neurocysticercosis.
    • Societal cost (monetary, stigma etc) not determined in many endemic areas.
  • Zoonosis: cost of treatment and control of the disease in humans

    Treatment of both taeniosis and neurocysticercosis are hindered due to access to diagnostics. Cost of treatment varies between cheap (<$1) and relatively expensive (>$3) in different endemic countries. Effective drugs are not universally available in all endemic countries.Neurocysticercosis related direct costs are mostly medical, while unemployment and inability to work are the main causes for indirect costs. The total annual costs due to neurocysticercosis -associated epilepsy has been estimated to amount to 5.9 million USD in Tanzania and 9.8 million USD in West Cameroon. In South Africa, the overall monetary burden was estimated to vary from 18.6 to 34.2 million USD depending on the method used to estimate productivity losses.In Mexico, on average 436 USD are lost per patient. If loss of future years of income and productivity due to neurocysticercosis -associated deaths is included, in total 54.3 million are lost, assuming that these individuals earned Mexico's median wage salary. Diagnosis and treatment of neurocysticercosis are expensive (CT or MRI scans needed) and country dependent. Cost-of-illness studies indicate costs for seizures of $126/ hospital visit (Zambia), $106/ neurocysticercosis epilepsy case (Tanzania), drugs for epilepsy are cheap, but the treatment usually must be continued for the whole life.Control in human is achieved most rapidly and optimally by applying an integrated, One Health approach tackling both the human and pig host. Cost of MDA in humans substantial but opportunities exist to integrate with other MDA programs including current TDA.

    GAPS :

    • Insufficient costing data available, need for ex-ante & ex-post evaluation of control options (cost-effectiveness/cost-benefit), using appropriate and standardised metrics for health and economic burden (either zDALY or monetary using Value of statistical life approach). If zDALY are used, the standard WHO-CHOICE cost-effectiveness thresholds ($/zDALY averted at <3 x GDP/capita) should be adopted.
    • Quantify the added benefit of MDA programmes for other diseases such as schistosomiasis.
    • A comprehensive review is required of the cost, availability, quality and registration status of drugs for treatment of taeniasis in the various endemic countries.
  • Direct impact (a) on production

    Economic loss estimates in the pig sector are based upon likely lower value/condemnation of carcasses within the informal sector.In China, around 200 million kg of pork with a value of more than 120 million is discarded annually due to porcine cysticercosis.In Tanzania porcine cysticercosis is responsible for an annual pig production loss of 2.8 million USD.In Zambia, a pig loses 55% of its value when infected and farmers are unable to sell their pigs pig in 95% of cases where porcine cysticercosis is suspected after tongue inspection.In Mexico, and additional 19 million USD were estimated to be lost due to porcine cysticercosis.

    Control of T. solium alone is not economically viable (Lao PDR) but high benefit/cost ratio were obtained when production limiting disease(s) (CSF) is (are) added in the assessment.Willingness to Pay for Cysvax® is present in Uganda pig farmers if premium price available for vaccinated pigs.Willingness to pay has also been reported from Zambia.

    GAPS :

    • Impact of infection on production parameters needs explicit quantification.
    • Impact of oxfendazole on production.
    • Impact of housing on production and other production limiting diseases.
    • Impact of infection on pig fertility and growth.
  • Direct impact (b) cost of private and public control measures

    Opportunity cost to meat inspectors for undertaking incision during inspection.

    GAPS :

    • Insufficient data available.
    • Exploration of traceability schemes for LMICs.
    • Ear-tagging for vaccinated/treated pigs could provide opportunity for visual only inspection.
    • Improved ex-ante & ex-post evaluations including of integrated scenarios.
  • Indirect impact

    Porcine Cysticercosis causes significant economic loss to farmers and meat traders through condemnation of infected meat and offal.

    GAPS :

    • Better quantification of price discrepancy of infected pigs needed.
    • Impact of enforcing condemnation of infected carcasses on food security indicators required (modelling).
  • Trade implications

  • Impact on international trade/exports from the EU

    EU import regulations. The meat is subject to meat inspection and certified fit for human consumption. OIE Terrestrial Animal Health Code 2019 chapter 15.4 provides guidance on importation of meat in relation to porcine cysticercosis.Currently no impact suspected as the affected pigs from endemic areas are usually not imported in the EU.

  • Impact on EU intra-community trade

    Evidence remains of (rare)autochthonous transmission within EU demonstrates need to enforce regulations.

  • Impact on national trade

    None expected.

  • Links to climate

    Seasonal cycle linked to climate

    Not known.

    GAP :

    Seasonality in relation to free roaming of pigs Seasonality in relation to the survival and distribution/spread of eggs in the environment. See also Section “Stability of the agent/pathogen in the environment”.

  • Distribution of disease or vector linked to climate

    No.

  • Outbreaks linked to extreme weather

    No.

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

    No.

Risk

  • Main risk from pigs is infection of humans and the difficulty in breaking the cycle. Human tapeworm carriers present a risk for infection of pigs and people.Increase of neurocysticercosis cases in Europe through mobility of tapeworm carriers from endemic countries.

    GAPS :

    • Relative importance of different transmission routes.
    • Data on human mobility/traveling.
    • Data on pig movement.

Conclusion

  • Cysticercosis is of major importance in LMIC where it is a neglected zoonoses and where the neural form is grossly under diagnosed and contributes to social and economic impairment. Control of the tapeworm in humans is important, but treatment is challenging due to the difficulty in finding the very few cases that exist. Improvements in sanitation, education and pig rearing practices in wealthy countries have seen cysticercosis disappear indicating that similar measures would be effective if they could be implemented in current endemic areas. However, these improvements have not been achieved sustainably to-date in any T. solium endemic region without simultaneous improvements in general living standards. Condemnation or thorough cooking of infected meat is important but in poor areas the presence of meat inspection is unlikely, and the discarding of infected meat is impossible to achieve. Control of infection in pigs either by vaccination or pre slaughter treatment with a compound which kills the cysticerci is possible although their costs and application may be too high to enable implementation in developing countries. Increasing knowledge and awareness creation are essential for uptake and sustained control.Elimination of the disease is theoretically possible but requires an integrated One Health approach and utilizing two or more control options in both hosts of the parasite at a high frequency. Additional close monitoring and surveillance will be essential for maintenance of control/elimination.

    GAPS :

    • Advocacy and financial support for implementation of existing, proven effective disease control and elimination measures.
    • Implementation studies.
    • Highly performing diagnostic tools.
    • Monitoring and surveillance systems.
    • Distribution and delivery of oxfendazole and vaccine.
    • One Health uptake, building One Health systems, engaging different sectors.
    • Economic benefits and cost sharing.

Sources of information

  • Expert group composition

    Sarah Gabriël, Ghent University, Belgium – [Leader].

    Marshall Lightowlers, Melbourne University, Australia.

    Seth O’Neal, Oregon Health & Science University and Center for Global Health, Peru.

    Bui Khanh Linh, Viet Nam National University of Agriculture, Vietnam.

    Lian Thomas, International Livestock Research Institute, Kenya.

    Kabemba Evans Mwape, University of Zambia, Zambia.

    Veronique Dermauw, Institute of Tropical Medicine Antwerp, Belgium.

    Chiara Trevisan, Institute of Tropical Medicine Antwerp, Belgium.

    Pierre Dorny, Institute of Tropical Medicine Antwerp, Belgium.

  • Date of submission by expert group

    29 September 2021.

  • References

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    • Dixon MA, Braae UC, Winskill P, Walker M, Devleesschauwer B, Gabriël S, Basáñez MG. Strategies for tackling Taenia solium taeniosis/cysticercosis: A systematic review and comparison of transmission models, including an assessment of the wider Taeniidae family transmission models. PLoS Negl Trop Dis. 2019 Apr 10;13(4):e0007301. doi: 10.1371/journal.pntd.0007301.
    • Donadeu M, Fahrion AS, Olliaro PL, Abela-Ridder B. Target product profiles for the diagnosis of Taenia solium taeniasis, neurocysticercosis and porcine cysticercosis. PLoS Negl Trop Dis 2017 11, e0005875.
    • Evans D, Mcfarland D, Adamani W, Eigege A, Miri E, Schulz J, Pede E, Umbugadu C, Ogbu-Pearse P, Richards FO. Cost-effectiveness of triple drug administration (TDA) with praziquantel, ivermectin and albendazole for the prevention of neglected tropical diseases in Nigeria, Ann Trop Med Parasitolv 2011.105(8).
    • Gabriël S, Mwape KE, Hobbs EC, Devleesschauwer B, Van Damme I, Zulu G, Mwelwa C, Mubanga C, Masuku M, Mambwe M, De Coster T, Phiri IK, Berkvens DL, Colston A, Bottieau E, Speybroeck N, Ketzis JK, Willingham AL, Trevisan C, Dorny P. Evidence for potential elimination of active Taenia solium transmission in Africa? N Engl J Med. 2020 Jul 23;383(4):396-397. doi: 10.1056/NEJMc1909955.
    • Hobbs EC, Mwape KE, Devleesschauwer B, Gabriël S, Chembensofu M, Mambwe M, Phiri IK, Masuku M, Zulu G, Colston A, Willingham AL, Berkvens D, Dorny P, Bottieau E, Speybroeck N. Taenia solium from a community perspective: Preliminary costing data in the Katete and Sinda districts in Eastern Zambia. Vet Parasitol. 2018 Feb 15;251:63-67. doi: 10.1016/j.vetpar.2018.01.001. Epub 2018 Jan 3.
    • Jansen F, Dorny P, Gabriël S, Dermauw V, Johansen MV, Trevisan C. The survival and dispersal of Taenia eggs in the environment: what are the implications for transmission? A systematic review. Parasit Vectors. 2021 Jan 29;14(1):88. doi: 10.1186/s13071-021-04589-6.
    • Lightowlers MW, Donadeu M. Designing a Minimal Intervention Strategy to Control Taenia solium. Trends Parasitol. 2017 Jun;33(6):426-434. doi: 10.1016/j.pt.2017.01.011. Epub 2017 Feb 21. PMID: 28236521
    • Michelet L, Dauga C. Molecular evidence of host influences on the evolution and spread of human tapeworms. Biol Rev Camb Philos Soc. 2012 Aug;87(3):731-41. doi: 10.1111/j.1469-185X.2012.00217.x. Epub 2012 Feb 9.
    • OIE links (see above).
    • OIE WAHIS.
    • Okello AL, Thomas LF. Human taeniasis: current insights into prevention and management strategies in endemic countries. Risk Manag Healthc Policy. 2017 Jun 1;10:107-116. doi: 10.2147/RMHP.S116545.
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Conclusions

  • Main perceived obstacles for effective prevention and control

    Lack of awareness and a clear mandate at national and international level (General lack of political commitment and advocacy).Lack of large-scale hybrid implementation studies.Lack of validated sensitive/specific and affordable diagnostic tests in humans and pigs.Lack of a One Health approach towards control, including One Health based implementation and evaluation of cost-effectiveness and cost-benefit.Lack of monitoring and surveillance systems.Registration of Cysvax® vaccine and oxfendazole for use in pigs not completed in many endemic countries.Distribution and delivery systems of Cysvax® vaccine and oxfendazole not setup yet.Cultural practises regarding latrine use, pig keeping and consumption of raw meat.

    GAPS :

    • Advocacy for initiation of control measures in highly endemic communities backed up with robust empirical evidence on cost-effectiveness.
    • International funding support for implementation of proven effective control measures and exploration of appropriate cost-sharing mechanisms for private sector uptake.
    • Support appropriate national surveillance systems for zoonoses to allow monitoring of control programmes.
    • Market studies on the potential uptake of porcine vaccination/treatment.
  • Main perceived facilitators for effective prevention and control

    Several facilitators can play a role, from different sectors such as value chain actors (pig farmers and traders), community actors (extension officers, WASH agents, health staff in dispensaries, traditional healers, community leaders, schools, media), policy level actors (Ministries for Agriculture, Health, Education, Social welfare, WHO/OIE/FAO).Other facilitators: Markets, legislation, financial support mechanisms needed for control initiatives.

    GAP :

    Lack of awareness at different levels.