African Swine Fever - available
Control ToolsDiagnostics availabilityAvailable mainly from Spanish Company . ELISA INGEZIM K3. Available mainly from Spanish Company. ELISA INGEZIM K3.
In house: OIE- ELISA and Immunoblotting from CRL for ASF. By Community Reference Laboratory for ASF:
Identification of the agent:
Serological tests:
Moderate potential to date, going increasing due to the current situation. None available but would be required of vaccines were available. GAP: no DIVA test Current methods are relatively rapid diagnostic tests but require centralized laboratory facilities and clinical specimen submissions which delays disease diagnosis. Pen side tests could improve the speed of diagnosis, Improved capacity for detection and control of African swine fever in East Africa and West Africa through supply of ELISA kits and PCR primers and training in their use. Application of sero-diagnostic tests and detection of asymptomatic carrier animals using sensitive DNA-based tests to provide improved surveillance and pathogen characterisation in regions where outbreaks have occurred. Vaccines availabilityNone. None. None. None. No vaccines available. Limited, as only found in Sardinia. Higher potential in Africa. Needs for authorisation in country to be used in. Until vaccines developed difficult to assess. Not at present. Attempts over many years to develop inactivated or attenuated vaccines to ASF have failed. Inactivated vaccines have conferred no protection. Attempts to attenuate the virus through passage in cell culture have not been successful, - DNA vaccine strategies have not been successful to date. - Deletion mutants strategies have not been successful to date. GAPS:
Pharmaceutical availabilityNone. Some studies are on going. Preliminary results obtained by “in-vitro” experiments using antiviral substances that antivirals might be used as an additional tool in ASF control. GAP: Lack of knowledge on antivirals therapy for ASF. None at present. Not applicable. Low. None. New developments for diagnostic testsKinetics of antibody response. Understanding of viral replication at genome and protein level.
Currently there are very good tools in terms of sensitivity and specificity for ASF diagnosis, however very few commercial kits (serological , PCR) available.
GAPS:
2-5 years. As a result of ASFRISK several new or improved techniques are coming soon as in house methods. More time for commercial availability. GAPS: Needs for more evaluation using a broad collection of field samples, including serum samples and tissue samples from domestic pigs, wildboars and African wild suids infected with current circulating strains in Africa, and Caucasus and Russia. Medium at Laboratory. GAP: Support of programmes for sampling in Africa regions, Caucasus and Russia through collaboration with the affected countries and international organisations. The serological recognition of carrier pigs has been vital for the success of eradication programmes. GAPS:
New developments for vaccines
GAP:
10 years. High.
New developments for pharmaceuticalsNone at present. Not applicable. Not applicable. None at present. Disease detailsDescription and characteristics.ASF (ASFV) is a complex large icosahedral enveloped DNA virus that exhibits many features common to both Iridovirus and Poxvirus families. This virus is currently classified as the only member of the family Asfarviridae. DNA structure is based on two variable ends and a conserved central region of about 125 kbp.The left and right variable ends of the genome encodes five multigene families (MGF). MGF are involved in the variability of the genome size within isolates, due to deletions and insertions of copies within MGF genes. In addition some MGF are involved in determining virulence and tick host-range. GAPS:
Suids, wild and domestic, are the natural host of ASFV. Several species of soft ticks have been shown to be ASFV reservoirs and vectors. ASFV don’t induce neutralising antibodies and this is why non serotype classification can be performed. ASFV genotyping based on the partial nucleotide genome sequence of the B646L gene, encoding the p72 protein allow to differentiate up to 22 distinct genotypes. The complete genome sequence of the E183L gene, encoding the p54 protein might be used also for subtyping. Enhanced discrimination between isolates can be obtained through the analysis of the central variable region (CVR) within B602L gene by characterization of the tandem repeats sequences (TRS). Different isolates belonging the same ASFV genotype vary in their ability to cause disease with some causing severe acute disease and high mortality while others exhibits subacute and chronic forms resulting in seroconversion. GAP: Biological and molecular characterization of current circulating isolates belonging to different genotypes in Africa. T°: Highly resistant to low temperatures. Heat inactivated by 56°C/70 min; 60°C/30 min pH: Inactivated by pH <3.9 or >11.5 in serum-free medium. Serum increases the resistance of the virus, e.g. at pH 13.4 - resistance lasts up to 21 hours without serum, and 7 days with serum Chemicals: Susceptible to ether and chloroform. Disinfectants: Inactivated by 8/1,000 sodium hydroxide (30 min), hypochlorites - 2.3% chlorine (30 min), 3/1,000 formalin (30 min), 3% ortho-phenylphenol (30 min) and iodine compounds. For animal housing and equipment, soaps and detergents, oxidising agents and alkalis are recommended. Soaps, detergents and Alkalis are useful to disinfect machinery, clothing, and vehicles, human housing etc and also Vircon is also recommended to be employed in aircraft. The procedure to be employed in feed, effluents, and manure, include bury or burn, or in the latter also by Acids and Alkalis. Insecticides (organophosphates and synthetic pyrethroids) for tick eradication, Survival: Remains viable for long periods in blood, faeces and tissues. Can multiply in vectors. Species involvedSwine are the only animal specie naturally infected by ASFV. The disease occurs through complex transmission cycles involving domestic pigs, wild boars, warthogs and bush pigs (African wild pigs). Domestic pigs, wild boars and feral/American pigs are susceptible to ASFV infection showing a range of clinical signs and mortality rates. ASFV usually induces an asymptomatic infection in wild African pigs. GAPS:
None. Soft ticks (Ornithodoros spp), including O. moubata and O. erraticus also act as reservoirs and vectors for virus transmission. Transovarial, and sexual transmission can occur. In Africa, ASFV is thought to cycle between newborn warthogs and the soft ticks (Ornithodoros moubata) that live in their burrows. Individual ticks can apparently remain infected for life, and infected soft tick colonies can maintain this virus for years. All the Ornithodoros spp experimentally infected until now were susceptible to ASFV infection. GAP: Geographical distribution in Europe and worldwide. Wild African pigs, most importantly warthogs (Phacochoerus aethiopicus), bush pigs (Potamochoerus porcus) and giant forest hogs (Hylochoerus meinertzhageni) are also infected but usually do not exhibit clinical signs, acting as reservoir hosts in Africa usually showing an asymptomatic infection. These species of wild pigs act as reservoir hosts of ASFV in Africa. Soft ticks of the Ornithodoros genus have been shown to be both reservoirs and transmission vectors of ASFV (ASFV). GAPS: Host-virus interaction in wild African pigs, determining asymptomatic infection. Description of infection & disease in natural hostsDirect and indirect contact between infected and susceptible pigs/wild boar and wild African pigs (warhogs). GAP: Studies on Neighbourhood transmission in densely population areas. Survivors of infection are virus carriers for life. ASF viruses produce a range of syndromes varying from peracute, acute to chronic disease and apparently healthy virus carriers. GAPS:
Incubation period is 3-15 days. Depending on the ASFV isolate virulence.
Unknown. GAP: Shedding kinetic patterns. ASF is generally spread via oral and nasal routes, but also by tick bite, cutaneous scarification, and intramuscular, subcutaneous, intraperitoneal or intravenous injection. The incubation period varies widely (4-19 days), depending on the ASFV isolate and the route of exposure.
By oral route, monocytes and macrophages of the tonsils and mandibular lymph nodes are the first involved. From these sites, the virus spreads through the blood and/or lymphatic system to the main sites of secondary replication – i.e., lymph nodes, bone marrow, spleen, lung, liver, and kidney. Viremia usually begins 4-8 days post infection and persists for weeks or months. ASFV is associated with red blood cell membranes causing hemadsorption.
GAP: Pathogenesis mechanism of infection by ASFV of different virulence are not well understood.
Zoonotic potentialASFV has never been shown to infect humans and is not considered to be a zoonotic pathogen. None. None. None. None. Impact on animal welfare and biodiversityASF outbreaks have an impact both due to the severity of the disease and with the introduction of control measures especially movement controls. European species of wild pigs are affected but this is not the case for African wild pigs. Slaughter of infected and in contact pigs. Geographical distribution and spreadAfrican swine fever was first recorded in Kenya in 1921 and is present as endemic in most sub-Saharan African countries. It spread to southern Europe in 1957 (genotype I) affecting different countries in Europe and central and south America. In Europe, ASF is still endemic in Sardinia (Italy) and since 2007, it has been notified in the Caucasus region and Russia Federation (genotype II, associated to those circulating in Eastern- southern African regions). The events have proved that the threat of ASF spreading to other regions remains and it is potentially devastating to the global pig industry. Source of information: www.oie.int and EU: Animal disease notification system (ADNS) GAPS: Education, awareness and preparedness of veterinary staff and producers. Become endemic mainly in developing countries, due to presence of complex transmission cycles which could involve a sylvatic cycle, a domestic cycle and a pig-tick cycle.
Greatly influenced by presence – and subsequent infection - of wild boar and vectors (wild African pigs and soft ticks acting as reservoirs).
GAPS:
None. Can be high mainly due to transport movements, and pig density. GAP: The role of wild boars in spreading the disease under different conditions. Potentially high and wide spreading, dependant on the movement of infected pigs/wild boars/ African wild pigs or infected meat or other pig products, and illegal movements. No. Not known. No. Not known. Route of TransmissionDirect transmission: contact between sick (domestic and wildboar) and healthy animals; contact with asymptomatic infected African wild reservoirs (carriers) and soft ticks Indirect transmission:
Ornithodoros ticks, where present, can act as transmission vector of the ASF virus. The virus can survive outside the pig for a long time, so the movement of contaminated vehicles, clothing, footwear and equipment can also spread disease.
GAP: The role of reservoirs in the transmission of the disease under different conditions. Detection and Immune response to infectionPigs often die before the development of a humoral response when infected with a virulent strain. Pigs which do not die will mount an antibody response and have significant levels of ASF specific cytotoxic T lymphocytes. Pigs will demonstrate a solid immunity to challenge from homologous strains but not heterologous strains. However there is an absence of neutralizing antibodies against ASFV. The ASF V replicates in porcine macrophages. The essential effectors immune mechanisms involved in protection against ASF are poorly understood. All attempts to develop an effective vaccine have been unsuccessful to date. GAPS:
Detection of antibodies and evidence of the virus genome or virus antigen. ASFV infection produce a long-term viremia at early time of infection. Specific IgG antibodies is detectable in blood from the first week and for a long period of time, months even year, in the surviving pigs. The early appearance and subsequent persistence of antibodies is the reason they are so useful in studying subacute and chronic forms of the disease. For the same reason, they play an important role in testing strategies implemented as part of eradication programmes. Main means of prevention, detection and controlControl of live animals and swine productos imports, control of waste food. Movement controls can all be successful. Quarantine. Once established in an area tick control becomes important using acaricides.
GAP: New control strategies and eradication models depending on the epidemiological situation, taking into account the complex transmission cycles, involving domestic pigs and the presence of wild boar and/or soft ticks and /or wild African pigs.
Since not vaccine is available, ASF diagnosis by virus detection and serological tests are critical for disease containment. Described in Diagnostic Manual 2003/422/EC and in the OIE Manual of Diagnostic Tests and Vaccines for Terrestrial animals, 2008: Virus detection and isolation :
ASF antibody detection:
GAPS:
None available at present. GAPS:
No effective treatment. GAP: Potential of antivirals. It may be of interest in ASF control. Rapid slaughtering of all pigs and proper disposal of cadavers and litter is essential. Thorough cleaning and disinfection. Movement controls.
GAP: Not always fully enforced. Efficient sterilisation of garbage. GAP: Don´t use swill feeding is not fully enforced in certain countries. In an outbreak surveillance of infected zone, and surrounding area is important. Pigs recovered from acute or chronic infections usually exhibit a viraemia for several weeks making the PCR test a very useful tool for the detection of ASFV in pigs infected with low or moderately virulent strains. In addition, Antibody detection techniques are very useful in detecting surviving infected animals. Recovered ASFV carrier pigs and persistently infected wild pigs constitute the biggest problems in controlling the disease. Eradication was successful in the Iberian Peninsula and in the Caribbean. Some common failures have been identified:
Invert in prevention is the best measure to avoid the significant socio-economical consequences of this disease. GAPS:
Cost can be are high. Outbreaks in Europe were controlled by animal quarantine and slaughter, frequently at a very high cost. Disease information from the OIEYes. http://www.oie.int/fileadmin/Home/eng/Media_Center/docs/pdf/Disease_cards/ASF-EN.pdf http://www.oie.int/index.php?id=169&L=0&htmfile=chapitre_1.15.1.htm http://www.oie.int/fileadmin/Home/eng/Health_standards/tahm/2.08.01_ASF.pdf Socio-economic impactNone. None. Variable depending on the strains involved. With 100% mortality can have a very high cost. This disease produces huge economic and social loses in many African countries, and impairs the development of the porcine industry. Disease outbreaks have occurred in Europe, South America, and the Caribbean; the cost of eradication has been significant. During outbreaks in Malta and the Dominican Re-public, the swine herds of these countries were completely depopulated. In Spain and Portugal, ASFV became endemic in the 1960s and complete eradication took more than 30 years. Main indirect impact is on the constraints on livestock production and the trade in pigs and their products. Loss of export markets. Trade implicationsControls on the movement, of pigs and products from infected countries. Likely ban on imports from affected countries. Quarantine measures. Movement controls on live pigs and their products from infected areas. Restrictions and controls on internal movements form the protection and surveillance zones. Main perceived obstacles for effective prevention and controlLack of vaccines, carrier recovered pigs, reservoirs in ticks and wild pigs in Africa.
GAPS:
Main perceived facilitators for effective prevention and controlAppropriate vaccines, ability to identify carriers, control of ticks.
RiskChanges in production practices and increased globalization have in-creased the risk of African swine fever being introduced into free areas. The main risk of ASF introduction into Europe is via infected pig meat or pig meat products, for example illegally imported pig meat or bush meat from infected countries or legally imported meat from areas with undetected infection. GAPS:
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