Classical swine fever: the European experience and a guide for infected areas.

Classical swine fever (CSF) (hog cholera) virus infection is still of world-wide concern, either because of the direct effects of the disease on swine breeding in areas where the virus is epizootic or enzootic, or as a threat in areas where the virus has been eradicated. The authors provide an overview of the characteristics of the disease. Special emphasis is placed on the chronic form of disease, particularly in the late stages of eradication programmes. In the early 1980s, the European Union (EU) was composed of countries which were officially free of the disease (absence of infection and no vaccination) and countries in which vaccination was either permitted or was compulsory. To ensure free trade between the Member States, an eradication plan was agreed upon and implemented. Initially, the plan consisted of a combination of vaccination with the Chinese strain of the virus and slaughter and removal of infected herds. Consequently, when the number of infected herds was low, vaccination was abandoned and the control of CSF was conducted exclusively by eradication (removal and slaughter). The United Kingdom, Austria, Denmark, Ireland, Luxembourg, Finland and Sweden ceased vaccination before 1980. In the other countries, vaccination was useful in controlling the last epidemics and was finally ceased as follows: France in 1983, the Netherlands in 1986, Belgium, Spain and Greece in 1988, Germany in 1989 and Italy in 1990. From 1990 onwards, no vaccination against CSF has been performed in the EU. New techniques for the diagnosis of CSF (for example, the enzyme-linked immunosorbent assay based on the detection of the p125 antigen of the virus) have been shown to be of value in the early detection of infected animals. In enzootic areas, the use of vaccines based on the Chinese strain has been successful. Vaccines with at least 100 PD50 of virus per dose are able to significantly limit the replication of virulent virus in the tonsils. Consequently, shedding of virus after infection can be reduced considerably. In heavily infected areas, vaccination plays a crucial role. The European experience shows that eradication may be achieved when vaccination with highly effective vaccines is combined with effective identification of swine, movement control, early diagnosis and the rapid elimination of infected herds.