African Swine Fever

African Swine Fever (ASF) is a highly contagious disease that causes severe bleeding in domesticated pigs and wild boars. The causative agent of the disease is the African Swine Fever Virus. High and sustained fever affecting animals of all ages are the defining characteristics of the acute form of ASF. Mortality amongst infected animals can be up to 100%.

ASF does not present any danger to human health. It is, however, highly contagious and can spread very fast among all pigs of an affected farm, and as such causes heavy economic loss.

What is African Swine Fever?

African Swine Fever (ASF) is a highly contagious viral disease caused by asfivirus, a member of the Asfarviridae family of viruses. The virus affects domesticated pigs and wild boars.

Clinical symptoms

The clinical signs of African Swine Fever may vary and emerge in different ways:

  • acute form: high fever, weight loss, lethargy, blood disorders associated with subcutaneous bleeding and jaundice, diarrhea, rapid mortality (2-3 weeks) and mortality rates up to a 100%
  • subacute form: less intense symptoms, lower mortality rates with animals passing away over a longer period of time
  • chronic form: non-specific symptoms, including episodes of fever, weight loss, breathing problems, chronic skin ulcers, arthritis. The disease may evolve over a period of several months.

The disease is highly contagious. Once it emerges on a farm, the symptoms spread very fast to all present (domesticated) pigs. High mortality is often reported among wild boar.

Transmission of African Swine Fever in animals

The African Swine Fever virus is very resistant and is transmitted by: 

  • direct contact with infected pigs or wild boars
  • indirect contamination caused by people, equipment or vehicles that have been in contact with the virus 
  • ingestion of contaminated and undercooked food waste
  • carriers: soft ticks of the Ornithodoros spp genus infected with the virus, but these ticks haven’t yet been reported in Belgium.

African swine (warthogs, red river hogs, forest hogs) can carry the virus without any clinical signs, and act as a natural reservoir of the virus.

African Swine Fever and humans

ASF does not present any danger to human health. It is, however, highly contagious and can spread very fast among all pigs of an affected farm, and as such causes heavy economic loss.

Information for health professionals

African swine fever is a highly contagious disease that requires notification. Any suspicion must immediately be reported to the local control unit of the FASFC.

No treatment and no vaccine exists to protect animals against African Swine Fever.

In countries that are free of African Swine Fever, prevention is based on strict import regulations to prevent infected animals or contaminated animal produce from entering the territory.

The African Swine Fever virus is highly resistant to environmental conditions. The virus survives 150 days at 4°C in boned meat, 140 days in raw ham and several years in deep-frozen carcasses. Hence, it is important to heat up unprocessed meat long enough and at a sufficiently high temperature to inactivate the virus. Prevention therefore also involves the proper disposal of food waste from aircraft, boats and vehicles coming from infected areas.

Hunters who enter contaminated areas, and especially areas at risk, must take all necessary precautions to avoid spreading the virus on their return.

It is very difficult to eradicate the virus in the infected areas, because it also infects wild animals (wild boars). Care should therefore be taken to avoid direct and indirect contact between wild boars and pigs.

Characteristics of the circulating virus

Following the detection of ASF cases nowadays, Sciensano characterises the circulating virus. The preliminary genetic results suggest that the ASF virus responsible of the wild boar cases occurring in Belgium belongs to the p72 genotype II, CVR-1, IGR-2 and MGF1 variants. These are the variants mostly circulating within the EU countries as well as described in Moldova (2016-2018), Ukraine (2012, 2015), Belarus (2013) and in certain areas of the Russia Federation (from the data available at the European reference laboratory in Spain). Full length sequencing is in progress.

 

Sciensano is the Belgian national reference laboratoy for African Swine Fever.

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