In recent weeks African swine fever (ASF) has been confirmed in Belgium, Bulgaria and the virus continues to take hold in China and escalate in central and eastern Europe. If you keep pigs or are involved in the pig industry it is important you are aware of the disease and how to help prevent it spreading further.
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 on into China, and has now been found in wild boar in Belgium, marking its entry into western Europe. The spread of this deadly disease is a cause of concern and experts in the field are fearing a pandemic. With no vaccine currently available, the only way to control it 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 has been confirmed to remain at ‘medium’ according to the Animal and Plant Health Agency (APHA), having only recently been raised to medium on a temporary basis. Despite the risk of exposure to the UK pig population being currently ‘low’ the authorities are stressing this is dependent on all pig keepers adhering to strict biosecurity procedures and continue to monitor the situation. Any suspected cases of ASF must be reported to Defra as it is a notifiable disease.
Three wild boar which were found dead in the Belgian region of Luxembourg, a few miles from the border with France, were confirmed as infected with ASF earlier this month and it is anticipated there may be further positive cases of the disease in the same area. It is unclear of the source of the outbreak but the considerable distance from other outbreaks in central and eastern Europe suggests it is not due to direct transmission from other infected animals. One possibility is that it may have been introduced by infected meat products, likely discarded by visitors to the area, though this has not been confirmed by any analysis.
Meanwhile China continues to struggle to contain its own outbreak causing considerable concern to the authorities and those in surrounding countries. China is home to over half the world’s pig population (around 500 million pigs); any further spread throughout China and neighbouring countries would be devastating. Widespread culling of infected animals and restrictions in trade and swill feeding have been imposed to help contain the disease but China continues to report more cases including in Inner Mongolia.
Wild boar act as a natural reservoir for ASF and can spread the disease to domestic pig farms – in eastern Europe, wild boar culling has been employed in some countries that are experiencing outbreaks. Authorities in Germany, Denmark and Bulgaria have also adopted this measure in hopes of reducing the number of boar that are able to carry the disease across borders, in addition to border fence improvements.
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
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 Defra’s Flickr pages. More information and a timeline of events can also be found on the National Pig Association’s website and from the World Organisation for Animal health (OIE).
Pirbright’s role in diagnostics and control
Rapid diagnosis and thorough surveillance of ASF are essential for its 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, 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 also researching another promising vaccine possibility by screening ASF genes for their ability to produce proteins that create an immune response in pigs. They are now looking to incorporate the most promising genes into a new vaccine. Pirbright researchers are also trying to understand how the virus evades the host’s immune system and how it is transmitted, which will aid in the development of potential vaccines and control of the disease. For more information about ASF, view our animated video below or visit www.pirbright.ac.uk/asfv.
African swine fever virus, clinical signs and vaccine research animated video