Epidemiology of malignant catarrhal fever in Switzerland

Malignant catarrhal fever (MCF) is a usually fatal infectious disease of ca ttle with global distribution. Based on the recent introduction of a diagno stic PCR assay and a competitive inhibition ELISA (ciELISA) epidemiological data were collected on field cases in Switzerland. Throughout a three-year period, an MCF incidence of 0.6 parts per thousand was observed, with a gr adient of cases from Eastern to Western Switzerland. While the cantons Wall is, Vaud and Geneva reported no and the remaining western cantons only repo rted a few cases, the highest incidence was observed in the cantons Appenze ll Innerrhoden, Lucern, Glarus, Grison, St. Gallen, Schwyz, and Thurgau. MC F occurred seasonally and an age-related clustering was also observed. Abou t 50% of all cases and all outbreaks with more than one animal in a single herd occurred between April and June. Animals between six months and two ye ars were strongly over represented. Observations on four surviving cattle s howed that the outcome of the disease is not invariably fatal and that thes e persistently infected cows can produce healthy negative calves. Investiga tions on the aetiology indicate that the main reservoir for OvHV-2 is in sh eep and possibly goats, while cattle do not normally harbor the virus. An O vHV-2 negative sheep herd was raised from lambs, which were reared colostru m free and in isolation from their mothers. The success rate clearly indica ted that vertical intrauterine infection is not the main mode of transmissi on among sheep. Therefore, horizontal, seasonally occurring transmission of OvHV-2 among sheep has to be assumed.