Field trials to assess the current formalin-inactivated killed vaccine against Babesia divergens used in Austria

In 1992 (Lienz in East Tyrol with 54 cattle) and 1993 (St. Anton / Scheibbs in Lower Austria with 116 cattle) two field trials in endemic areas of Aus tria were carried out during a pasture period in ord er to assess the succe ss of the vaccine. Different Vaccination schedules (normal vaccination sche dule: 2 x 3 mi vaccine given s.c., 2 weeks apart; the first vaccination sho uld be carried out 5 - 6 weeks prior to pasture) have been used. In fixed i ntervals blood samples (before, during and after pasture period) were taken to assess the formation of specific antibodies against Babesia divergens b y the indirect fluorescent antibody test (IFAT). In the age group examined (5 months to 10 years) neither race nor sex had a n evident influence on the formation of antibodies. This study showed, that an IFAT - antibody titre during the whole pasture p eriod of 1: 64 seemed to be sufficient to protect cattle against Babesia-in fections. The best results with regard to the permanent activity of the ant ibody titre during the pasture period were obtained by vaccinating twice in a previous year and a boostering in the following year (a single boosterin g should be sufficient). It may be worthwhile to consider a third vaccinati on in the first year in order to optimize the efficiency of the vaccination schedule and protection of animals as well.