African Swine Fever
| What is African swine fever? African swine fever (ASF) is an acute, hemorrhagic, severe infectious disease caused by African swine fever virus (ASFV) infected domestic pigs and various wild boars such as African wild boar and European wild boar. |
| Clinical signs Clinical signs and mortality rates can vary according to the virulence of the virus and the type/species of pig: Acute forms of ASF are characterised by high fever, depression, anorexia and loss of appetite, haemorrhages in the skin (redness of skin on ears, abdomen and legs), abortion in pregnant sows, cyanosis, vomiting, diarrhoea and death within 6-13 days (or up to 20 days). Mortality rates may be as high as 100%. Subacute and chronic forms are caused by moderately or low virulent viruses, which produce less intense clinical signs that can be expressed for much longer periods. Mortality rates are lower, but can still range from 30-70%. Chronic disease symptoms include loss of weight, intermittent fever, respiratory signs, chronic skin ulcers and arthritis. Different types of pig may have varying susceptibility to ASF virus infection. African wild suids may be infected without showing clinical signs allowing them to act as reservoirs. |
| Diagnosis The clinical symptoms of ASFV infection are very similar to classical swine fever, and the two diseases normally have to be distinguished by laboratory diagnosis. This diagnosis is usually performed by an ELISA or isolation of the virus from either the blood, lymph nodes, spleen, or serum of an infected pig. |
| Transmission and spread The epidemiology of ASF is complex and varies depending on the environment, types of pig production systems, the presence/absence of competent tick vectors, human behaviour, and the presence/absence of wild pigs. Routes of transmission can include: 1. Direct contact with infected domestic or wild pigs; 2. Indirect contact, through ingestion of contaminated material (e.g. food waste, feed, or garbage); 3. Contaminated fomites, or biological vectors (soft ticks of the genus Ornithodoros) where present. |
