[Aujeszky's disease. Studies on the possibility of differentiating between contaminated pig-breeding farms and farms on which the pigs have been inoculated with the Bartha vaccine (author's transl)].

The serological studies reported in the present paper were done on forty-one pig-breeding farms contaminated with Aujeszky's disease and four farms that were free from this disease and on which fifty per cent of the animals had been inoculated with the Bartha vaccine. The serological studies were based on the serum neutralization test (SN test). On contaminated farms, the majority of the animals present at the time of outbreak of the disease were serologically positive. Comparison of the serological findings on farms on which there had been outbreaks of the disease from two to seven and from seven to twelve months previously, showed that there was hardly any difference in titre levels between the two groups. Of twenty-eight breeding boars used for service at the time of the outbreak, twenty-one per cent were serologically negative. Serological studies in breeding gilts showed that virulent virus was only transmitted up to two months after the outbreak of the disease.