Context-China has reported a new outbreak of African swine fever that is threatening the country’s vital pork industry

About

African Swine fever

• African swine fever is a viral disease of pigs and wild boar that is usually deadly. There are neither vaccines nor cures. For this reason, it has serious socio-economic consequences in affected countries. Humans are not susceptible to the disease

Transmission and spread

Healthy pigs and boar usually become infected by:

• Contact with infected animals, including contact between free-ranging pigs and wild boar.
• Ingestion of meat or meat products from infected animals – kitchen waste, swill feed, infected wild boar (including offal).
• Contact with anything contaminated by the virus such as clothing, vehicles and other equipment.
• Bites by infectious ticks.

Movement of infected animals, contaminated pork products and the illegal disposal of carcasses are the most significant means of spread of the disease.

Sign and symptoms

• The typical signs of African swine fever are similar to classical swine fever, and the two diseases normally have to be distinguished by laboratory diagnosis. 
• Symptoms include fever, loss of appetite, lack of energy, abortions, internal bleeding, with haemorrhages visible on the ears and flanks. Sudden death may occur. 
• Severe strains of the virus are generally fatal (death occurs within 10 days). Animals infected with mild strains of African swine fever virus may not show typical clinical signs.

Prevention and control

• Currently there is no approved vaccine for ASF.
• Prevention in countries free of the disease depends on implementation of appropriate import policies and biosecurity measures, ensuring that neither infected live pigs nor pork products are introduced into areas free of ASF. This includes ensuring proper disposal of waste food from aircraft, ships or vehicles coming from affected countries and policing illegal imports of live pigs and pork products from affected countries.
• During outbreaks and in affected countries, control of ASF can be difficult and must be adapted to the specific epidemiological situation.
• Classic sanitary measures may be employed including early detection and humane killing of animals (with proper disposal of carcases and waste); thorough cleansing and disinfection; zoning/compartmentalisation and movement controls; surveillance and detailed epidemiological investigation; strict biosecurity measures on farms.

Is it a public health threat?

• ASF cannot be transmitted to humans through contact with pigs or pork.
• ASF only affects members of the pig family.

Why is ASF not a human threat? 

• Most viruses demonstrate some degree of host restriction; they replicate in one cell type or host and not in another. While there are exceptions, this is the general rule, not the exception. In the case of ASF virus, there is no evidence supporting either subclinical or clinical infection of humans.
• The host restriction in ASF virus is likely due to the absence of susceptible and permissive cells needed for viral replication. It could also be related to the inability of the virus to overcome intrinsic and innate host responses generated following ASF virus exposure.