African swine fever virus (ASFV) causes a devastating disease of pigs. It is a large complex DNA virus and is the only member of the Asfarviridae family, genus Asfivirus. ASFV has several layers that surround a dense core containing its DNA genome. The image above shows virus particles at different stages of assembly.
African swine fever virus (ASFV) causes a severe disease in domestic pigs and wild boar that can result in death in almost all pigs that are infected. There is currently no treatment or vaccine widely available and therefore biosecurity measures are essential to prevent an outbreak from spreading. The clinical signs of ASF can vary but are similar to some other pig diseases. Signs typically occur 3-15 days after infection.
The early signs are non-specific and include:
- High fever, lethargy, and loss of appetite.
- Pigs may die suddenly without further disease signs.
At later stages, further signs may be observed including:
- Reddening of the skin (visible only in pale-skinned pigs), with patches appearing on the tips of ears, tail, feet, chest, or under the belly.
- Diarrhoea, vomiting.
- Laboured breathing.
- Swollen red eyes, eye discharge.
- Abortions, still-births.
- Increasing morbidity and unwillingness to get up.
In severe cases death can sometimes be the only sign of infection, with a case fatality rate as high as 100%.
- African swine fever is a notifiable disease and should be reported.
Please see the Defra website for advice on how to spot and report the disease. Guidance to pig keepers on preventing the disease is also available.
Images of ASF clinical signs:
Pictures copyright The Pirbright Institute.
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The disease can be spread directly through contact. It can also be indirectly transmitted through feeding infected pig meat and /or pork products, by a species of soft tick in some regions and possibly blood sucking flies or insects, and through contaminated objects (fomites) such as vehicles, clothes, equipment etc.
Since emerging in the early 1900s from East Africa, ASF has moved through sub-Saharan Africa and has been reported from 32 countries since 2005. On two occasions the virus has spread out of Africa. The first, a genotype I strain in 1957 and 1960, was introduced to Portugal and spread in Europe, the Caribbean and Brazil. This incursion was eradicated from all affected countries apart from Sardinia by the mid 1990s. However, a second incursion to Georgia in 2007, of a genotype II strain has continued to spread globally first to the Russian Federation and Eastern Europe. Since entering the European Union in 2014 numerous countries have been affected and disease continues to be reported in over 15 European countries. In August 2018, ASF was first reported from China, the world’s largest pig producer, and rapidly spread throughout China and to 16 Asian and 2 Oceanic countries. In 2021 the disease reappeared in the Americas after an absence of almost 40 years, having been introduced in Dominican Republic and later in Haiti. Recent new disease spread in 2022 includes in Europe to the Italian mainland, further west in Germany and in Asia to Nepal and further spread to Kerala in India. In all, 4 countries reported the first occurrence of ASF, and 4 countries reported the first occurrence in a new zone in 2022. This highlights a continuous spread of the disease into new countries, and new regions in countries already affected.
For up to date information on the location of ASF outbreaks, visit the World Organisation of Animal Health Information Database.
Impact for Society – what are we doing?
Scientists at The Pirbright Institute have been working on understanding the virus since the 1960s.
Pirbright researchers are currently developing different types of ASF vaccines (a live attenuated vaccine and a subunit vaccine) with the aim of producing one that will protect pigs from this deadly disease. They are also working with ViroVet to produce ASF antivirals that could lower virus replication in pigs and limit clinical signs, which would form an important part of any feed-based strategy to control the virus.
As the World Organisation for Animal Health (WOAH) Reference Laboratory for ASF, Pirbright provides surveillance and diagnosis of ASF globally and continually works towards improving tests to detect the virus. Pirbright experts also provide advice to Department for Envionment, Food and Rural Affairs (Defra) and WOAH, and have helped to provide resources for vets that will help them to identify ASF quickly should it ever present in the UK.
Pirbright is the consortium lead for DEFEND which is tackling the emergence of African swine fever and lumpy skin disease in Europe, in partnership with 31 other consortium members including industry partners ID-VET and Zoetis. (EU H2020 research programme 773701).
Participation in other international projects includes the ASFV interactome project which has six European partners.
- Downloadable factsheet
- Veterinary resource: ASF clinical signs
- Communication tools on ASF. Developed jointly by the WOAH and FAO as part of the “ASF kills pigs” campaign the materials are available in English, French, Spanish, Russian and Chinese and include messages targeted at key stakeholders (veterinarians, pig farmers and decision-makers) on actions they can take to prevent and control ASF.
- The WOAH's ASF information
- The FAO's most recent ASF updates