African Swine Fever
African swine fever is a contagious animal disease of wild and domestic pigs. For humans, African swine fever is not dangerous. However, travelers coming from areas with African swine fever can transmit the disease! The disease is caused by a virus, there is no vaccine. It is fatal to domestic pigs and wild boar. The virus can remain contagious in blood, meat, bones and food for months and can be transmitted through contaminated shoes, clothing, tools and containers. Dogs and other animals cannot contract it. Here's what to watch out for:
- Bringing meat, sausage, bacon, etc. from non-EU countries into European Union countries is prohibited. As a rule, do not bring food made from pork and wild boar meat from home slaughtering
- Throw meat and sausage leftovers only in closable waste containers
- Feeding food scraps to domestic pigs and wild boars is prohibited
- If possible, avoid any contact with domestic and wild pigs.
Transmission occurs either via the bite of infected ticks (at present, this transmission route is not significant in Europe), through direct contact of susceptible (wild) pigs with infected conspecifics or their virus-containing body fluids, or through ingestion of virus-containing food waste. Since the virus is very resistant, it remains infectious to some extent even after drying or processing/maturing in raw meat products such as raw ham or salami.
The symptoms are strongly dependent on the virus strain. The strain currently present in Europe of the so-called genotype 2 usually leads to highly febrile, severe general diseases in domestic and wild pigs of all ages, in which bleeding into the skin and internal organs can occur. Affected animals usually die from the disease before they develop antibodies. However, there are also virus strains that lead to milder courses of the disease.
Situation in Austria
Austria has so far been spared from African swine fever, but it occurs in some direct neighboring countries such as Germany, Italy, Slovakia, the Czech Republic and Hungary, but also in Poland, the Baltic States (Estonia, Latvia, Lithuania) and many Eastern and Southeastern European countries (Romania, Bulgaria, Serbia, Northern Macedonia, Greece, Moldova, Ukraine, Russia). The main risk for Austria remains the entry from the Eastern outbreak areas in Europe.
In the Austrian animal disease radar, information on the international situation and spread of the most important animal diseases and epizootics relevant for Austria is assessed and compiled. In this way, possible risks for Austria can be identified and communicated at an early stage. The animal disease radar is published monthly.
In Austria, since the end of 2019, for the purpose of early detection, all feral pigs found dead must be reported and examined by AGES for the ASF virus. In addition, an examination of abortions as well as of clinically or pathologically conspicuous domestic pigs is also carried out. In 2022, 1,456 samples from 1,454 domestic pigs were examined by official order, only a fraction of which took place in the course of exclusion examinations. In the same year, 1,809 wild boars were tested for ASF virus. In none of these cases was the virus detected.
African swine fever virus (ASFV) is a DNA virus that is the only virus belonging to the family Asfarviridae, genus Asfivirus. ASFV has a double-stranded DNA genome with a very complex structure, approximately 170,000 to 192,000 base pairs in size. There is only one serotype, but based on the viral p72 gene, 24 different genotypes are currently distinguished. The virus shows a tropism to macrophages and is therefore present in high amounts in the blood and all blood-containing organs (particularly high viral loads are found in the spleen). ASF is a notifiable disease.
The transmission route via ticks of the genus Ornithodoros, which was important in Africa and historically also in Europe, does not play a role in Europe according to current knowledge. Domestic and wild pigs become infected through contact with infected conspecifics, ingestion of food waste containing the virus, and possibly through contaminated objects such as farm equipment, vehicles, and clothing. Based on current knowledge, feral pigs that die of ASF or their carcasses are an important source of infection for conspecifics. Early removal of these carcasses is therefore of great importance in the infected area.
The incubation period is 4-19 days The most important symptoms are fever (40.5 °C to 42 °C) and apathy. After the pathogen enters the host, viremia with fever occurs first. Many African wild pigs (e.g., warthogs) are inapparently infected with the virus. Pigs may also carry the pathogen without clinical signs (asymptomatic carriers). Pigs with symptoms show typical clinical signs, which depend on the virus strain. In Europe, ASF virus genotype II is common and usually leads to an acute course of the disease.
There are several forms of progression - depending on the virulence of the pathogen:
Peracute - acute form (usually caused by highly virulent ASF virus, e.g., ASF virus genotype II).
- Fever (40.5 °C to 42 °C)
- Leukopenia and thrombocytopenia (48 to 72 hours)
- Erythema = redness of the skin: ears, tail, distal extremities, abdomen, and chest
- bleeding in internal organs (spleen, lymph nodes, stomach, kidneys, lungs)
- increased pulse rate
- increased respiratory rate
- diarrhea (usually also bloody)
- Death occurs within 6-13 days (up to 20 days). The mortality rate is 90-100% in domestic and wild pigs.
Subacute form (usually due to moderate-virulent ASF virus).
- Symptoms are not as severe as in the acute form; abortions occur more frequently. The course of the disease lasts 5-30 days. Death occurs within 15-45 days. Mortality rate is lower than in the acute form (30-70%).
Chronic form (usually caused by low-virulence ASF virus).
- Symptoms are not as pronounced as in the acute form
- weight loss
- irregular temperature fluctuations
- breathing problems
- chronic skin ulcers partly skin necrosis
- adhesion of the lung
- joint swelling
- course of the disease lasts about 2-15 months
- low mortality rate (< 20 %)
Suitable sample materials are:
- EDTA blood (much lower virus loads are to be expected in serum)
- Blood-containing swabs (only from feral pigs found dead or symptomatic animals)
- Blood-containing organs (especially spleen, liver, kidney, lymph nodes, tonsils)
- Bones containing marrow (e.g. humerus, femur, mandible, sternum)
Detection of ASFV from above materials is possible by the following methods:
- PCR (EDTA blood, blood-containing swabs, organs and bones).
- Virus isolation (EDTA blood, organs and bones)
- ELISA (serum)
- Immunoperoxidase monolayer assay
In all cases, specimen shipment to the laboratory should ideally be performed with the addition of refrigerants and consideration of the appropriate transport regulations (UN3373) by a logistics company authorized to do so.
Last updated: 10.10.2023