The National Pig Association (NPA) is becoming increasingly concerned about the risk of African Swine Fever (ASF) spreading to the UK since it was confirmed in four wild boar in the Luxembourg region of Belgium, near the French border on September 13th.

A 630 square km Infected Zone has been set up around the infected area and various measures put in place to try and eradicate the virus and keep it out of domestic pigs. This included culling around 4,150 domestic pigs on a small number of commercial premises and numerous smallholdings. French hunting federations have also erected an electric fence on the Belgian border in a desperate attempt to keep the disease out of their wild boar population. Although the outbreak has been contained, there have now been124 cases of ASF confirmed in wild boar in the Infected Zone.

The disease is characterised by pigs developing haemorrhaging on their skin and internal organs and can result in death within ten days of infection. Financial consequences of an outbreak are substantial, as once the virus has been detected on a pig farm the entire population must be culled.

ASF, which affects only wild boars, warthogs, bush pigs and domestic pigs is endemic in sub-Saharan and West Africa and was first detected in Kenya in 1921.

The disease is transmitted among pigs by direct contact with infected animals, their carcasses and bodily fluids, or by consuming contaminated meat, usually discarded by humans. Any objects from infected zones, such as boot soles or tyres, can also carry the virus as they may transfer sources like blood, tissues, secretions and excretions of dead or sick animals.

Eastern Europe has witnessed several outbreaks of the virus over the summer, with Romania most affected. The first case was reported in January near the Ukrainian border, and Romania has reported over 900 outbreaks since, mostly among backyard animals. Bulgaria, the Czech Republic, Latvia, Lithuania, Hungary, Poland, Russia, Moldova and Romania have reported over 355,000 cases between them since 2014.

China is also struggling to control the disease which was first reported on August 3rd. Since then there have been 53 outbreaks of ASF in domestic pigs in 13 provinces. The most recent reports are in South East China and represent a significant geographical jump.

The source of the first outbreaks in China is unknown at present, but the Chinese Authorities have reported that over 60 per cent of the outbreaks are associated with feeding swill or catering waste to pigs. Nevertheless, there are other pathways which need to be considered, including the movement of infected pigs over long distances to market.

Soft-bodied tick species are also known to be involved in the transmission cycle of ASF. The virus can persist for several years in the absence of infected pigs when ticks are present, hindering eradication efforts in domestic pigs and wild boar/feral pigs.

There are thirteen species of soft-bodied ticks present in southern China, although it is not known how effective they are as vectors of ASF. Therefore this jump not only represents a spread of the disease towards other countries in south-east Asia, but also opens up the possibility for establishment of the virus in the resident tick population, so facilitating persistence.

Humans are still the most likely way the disease is spread. Japan's farm ministry confirmed that sausages in a passenger's luggage at New Chitose Airport, in Hokkaido tested positive for the disease. The virus has not yet been detected in Japan and this was the first recorded case of the virus being brought to the country from overseas.

The incident dates back to October 1 when the passenger from Beijing was found to have 1.5kg heat-processed, vacuum-packed sausages that later tested positive for the virus.

Humans are also the most likely route of infection for the wild boars in Belgium and there has been speculation it could have been brought by soldiers that had returned from military exercises in the Baltic States. In the rest of Europe the main factor for spread has been wild boar movements, and illegal pig and pork trading. Another consideration is the Schengen zone that allows Europeans to travel between 26 countries without any border checks.

Domestically, the main worry is that lorry drivers from Eastern Europe regularly enter the UK stocked up with enough food to last the journey, posing a real threat to domestic pig producers from scraps discarded at lay-bys.