[Serologic studies on the occurrence of bovine ehrlichiosis in the cantons Zürich, Schaffhausen, Thurgau, St. Gallen and Obwalden].

The purpose of this study was to investigate the geographical distribution of bovine ehrlichiosis in the Cantons Zürich, Schaffhausen, Thurgau, St. Gallen and Obwalden. To this end, an indirect immunofluorescence assay was established. The diagnostic sensitivity and specificity was estimated to be close to 100% based on the results obtained with several reference sera from the US National Veterinary Services Laboratories and the seroconversion panels of 20 heifers and cows. Blood samples from 2557 healthy cattle were tested for antibody response against Ehrlichia phagocytophila. Ninety-three animals (3.6%) were seropositive with titers ranging from 1:20 to 1:320. Most of the positive animals were found in the area north of lake Zürich spanning to the german border, in the area between Walensee and Bad Ragaz, the Rhine valley and Klein Melchtal. All seropositive animals had grazed on pastures or alps with a favourable biotope for the tick Ixodes ricinus.