Bovine mastitis induced by a common intestinal Chlamydia psittaci strain. A pathogenetic and serological investigation.

Cattle are frequently infected with a persisting intestinal Chlamydia psittaci strain, which through the manure deposit will contaminate their surroundings. The potential of such a strain (ROS) for inducing mastitis was demonstrated in 7 cows, inoculated in 1 udder-quarter through the teat canal, and the pathogenetic events provoked were compared with those of more virulent and infrequently isolated strains, viz. the EAE and the SBE strains. The chlamydial agent caused during a 2–3 weeks period a local, self-limiting exudative mastitis with a fibrinous secretion, leading to a state of reduced milk production. Increasing titres of complement fixing and agglutinating antibodies were demonstrated in whey and serum. The results from the 2 serological methods did not substitute each other entirely, so that both tests had to be employed in order to demonstrate the presence of the agent in all cases. Demonstration in 1 animal showed that the infection left the gland with resistance to reinfection.