Updated 28 November 2019.
African swine fever (ASF) is caused by the highly infectious ASF virus (ASFV) and is often fatal in all pigs and wild boar. The virus does not cause disease in humans, but it does pose a significant threat to food security and has a substantial impact on the economy, especially on trade and farming.
Initially found in parts of Africa, the virus has spread throughout eastern and central Europe, and has been found in wild boar in Belgium, marking its entry into western Europe. ASF has also reached many countries in Asia, including China, which is home to half the worlds pig population. You can find out about the spread of the disease on the World Organisation for Animal Health (OIE) Information Database. With no vaccine currently available, the only way to control ASF is through strict biosecurity, restrictions on trade, culling and destruction of infected carcasses.
The lack of a vaccine makes the control of ASF substantially more difficult, particularly due to the many transmission routes available, which have varying impacts depending on the region. The risk of ASF introduction to the UK through imports has been stressed by the government, who launched an awareness campaign at the UK's borders to stress the importance of not bringing in infected meat. Authorities are also stressing that all pig keepers should adhere to strict biosecurity procedures and continue to monitor the situation. Any suspected cases of ASF must be reported to the Department for Environment, Food and Rural Affairs (Defra) as it is a notifiable disease.
How the disease spreads
African swine fever can be spread through infected meat and meat products as well as vehicles, clothing, footwear and equipment (fomites). It is critical to ensure strict regulations around imported meat and meat products and biosecurity are adhered to. The virus is able to survive in frozen, smoked, dried and cured meat for months or even years, so stringent import regulations for pork products are an essential preventative measure. It also remains in the faeces and blood of infected animals after death, so it is important carcasses are disposed of properly.
Preventing the spread of ASF to the UK
The Animal and Plant Health Agency (APHA) has stressed that it is illegal to feed domestic food waste or catering waste of any description to farm animals in the UK. This includes all pigs, whether kept commercially, on small holdings or as pets.
You should not feed:
- Food scraps and catering waste from any restaurant or commercial kitchen (including vegan kitchens) as this is illegal.
- Domestic kitchen waste or scraps.
- Raw, partially cooked or fully cooked meat and fish (including shellfish).
- Dog and cat food.
Pig keepers are also urged to ensure their biosecurity measures are robust in order to help prevent infection including routinely providing dedicated clothing and boots for workers and visitors, limiting visitors to a minimum, and preventing outside vehicles which may be contaminated from coming on to pig premises.
The signs of ASF are very similar to classical swine fever, and it can be difficult to spot since not all animals develop clinical symptoms and can die suddenly without showing signs of being ill. The main symptoms to look out for include:
- loss of appetite
- lack of energy
- sudden death with few signs beforehand
Other signs include: vomiting, diarrhoea (which can be bloody), red skin (particularly on the ears and snout), laboured breathing and coughing, abortions and weakness including an unsteady gait. Together with APHA, Pirbright has produced a resource detailing the clinical signs of pigs infected with ASF and photos can be found on Pirbright's ASF page.
Pirbright’s role in diagnostics and control
Rapid diagnosis and thorough surveillance of ASF are essential for ASF control, services which Pirbright provides globally as the World Organisation for Animal Health (OIE) Reference Laboratory for ASF. Pirbright advises Defra and OIE and works towards improving tests to detect the virus more accurately and rapidly. The reference laboratory also organises scientific and technical training and provides diagnostic reagents to laboratories around the world and collects data to monitor the global patterns of disease distribution.
ASF researchers at Pirbright, led by Dr Linda Dixon and Dr Chris Netherton, are advancing the hunt for a safe and effective vaccine. Scientists are genetically modifying the ASF virus so that it has a reduced ability to cause infection – known as a live-attenuated vaccine. Pigs that have been exposed to the modified strain are protected against further infection by a natural ASF virus, indicating this method could be developed further. The team is researching another promising vaccine possibility by screening ASF genes for their ability to produce proteins that create an immune response in pigs, and are now looking to incorporate the most promising genes into a new vaccine. 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.
For more information about ASF, view our animated video below or visit www.pirbright.ac.uk/asfv.