[Chlamydial infection in herds of cattle with abortions]

A study was carried out for the presence of chlamydia on 103 farms with records of abortions. Employed were methods of infecting chick embryos via the yolk sac, the complement-fixation test, and electron microscopy. Five chlamydia strains were isolated from aborted fetuses on 5 out of 11 studied farms. Statistical processing of the serologic results obtained revealed that on 20 farms up to 71 per cent of the cows that miscarried were serologically positive for chlamydia, showing titers within the range of 1:8-1:1024 and an average geometrical titer of 34. On other 35 farms these indices were 23.45 per cent, 1:8-1:512, and 28, respectively. On 48 farms serologically negative were 98.94 per cent of the cows that miscarried, while the average geometrical titer was less than 2. Serologic conversion at a replicated serologic investigation was established in 4 out of 5 enzootics of abortions. No chlamydia antibodies were found in sera taken from a total of 4,804 normal cows and heifers from sound farms.