African swine fever (ASF) is the main threat to the development of the African pig industry. Its destructive potential was fully appreciated when, in 1957, it made its first appearance outside Africa. Heavy losses were experienced in areas of high pig production in Europe and subsequently the Caribbean and Brazil. Eradication was achieved only at a cost of several billion dollars and, for the Iberian Peninsula, took more than 30 years. ASF remains endemic in Sardinia (Italy). In Africa, re-emergence of the disease in 1994 has devastated pig production in many countries and the situation in others needs to be clarified. Its extremely high potential for transboundary spread has placed all the countries in the region in danger and has raised the spectre of ASF once more escaping from Africa. It is a disease of growing strategic importance for global food security and household income.
The extremely rapid spread of ASF is due to its highly contagious nature and the ability of the virus to persist in a protein environment, including meat products, for long periods. The fact that mortality is nearly 100 percent creates an enormous surplus of dead pigs, which constitute a huge reservoir of virus. Since no vaccine exists, the only means of control is by compulsory slaughter, avoidance of which leads to clandestine movement of potentially infected pigs. The most important factor that has been identified as contributing to the spread of this devastating disease is lack of early detection due to insufficient knowledge/experience on the part of farmers and pig breeders and among technical personnel regarding the manifestation of the disease.
The epidemiology of ASF is complex. Control strategies need to be developed taking into account the cycle in which the virus is maintained, as well as the type and level of pig production in an area. Where the sylvatic cycle (involving the wild suids and argasid ticks) occurs and pig production is of the commercial type, control is maintained by separation between wild suids and domestic pigs. When domestic pigs and their products constitute the source of infection and large populations of free-ranging pigs are kept in traditional systems, a holistic approach to control is required that takes into account socio-economic factors as well as animal health. The golden thread, without which any control strategy is destined to fall apart, is the personal involvement of all operatives in pig production, with the state authorities in the control programme. From their involvement, the factors that reduce the risk of ASF, from better pig-keeping systems to control of imports, can develop. Most important for disease control, however, is a surveillance system that will ensure early warning and reaction. The foremost prerequisite for this is recognition of the disease.
This content is got from FAO manual, for more information see: http://www.fao.org/docrep/004/x8060e/x8060e00.htm
Charles Masembe (BVM, MSc., PhD),
Associate Professor (Molecular Genetics & Evolution),
Wellcome Trust Fellow,