Epidemiology of classical swine fever in Germany in the 1990s

In Germany, 424 outbreaks of CSF in domestic pigs and a great number of cas es in wild boar were recorded between 1990 and 1998. Most of the federal st ates ('Bundeslander') were affected. Epidemiological data from field invest igations combined with genetic typing allowed to distinguish seven unrelate d epidemics and a number of sporadic outbreaks in domestic pigs. Detailed epidemiological data was available for 327 outbreaks. It was found that 28% of these were primary outbreaks. Most of them were due to indirec t or direct contact to wild boar infected with CSF virus or swill feeding. Infected wild boar remain the main risk for domestic pigs. The most frequen t sources of infection in secondary or follow up outbreaks were the trade w ith infected pigs, neighbourhood contacts to infected farms and other conta cts via contaminated persons and vehicles, respectively. An increased risk of virus transmission from infected herds to neighbourhood farms was observ ed up to a radius of approximate to 500 m. More than two thirds of the infected herds were discovered due to clinical signs. About 20% were identified by epidemiological tracing on and back. Th ese were scrutinised because contacts to infected herds were evident. In co nclusion, tracing of contact herds and clinical examination combined with c arefully targeted virological testing of suspicious animals is likely to be the most important measure to immediately uncover secondary outbreaks. Obl igatory serological screening in the surveillance and the restriction zones do not seem to be efficient measures to detect follow-up outbreaks. (C) 20 00 Elsevier Science B.V. All rights reserved.