Observation on chemotherapy in cows chronically infected with Coxiella burnetii (Q fever).

Pregnant dairy cows chronically infected with Coxiella burnetii were treated orally with 8 mg of chlortetracycline per kilo of body weight each day for 30 days during their dry period. With the exception of a sample of mammary fluid collected at 28 days, rickettsiae were not recovered from the mammary fluids after the second week of treatment. In addition, the organism was not recovered by mouse inoculation from placental tissues, colostrum or calf tissues that were examined after parturition. Results of oral chemotherapy studies in cows and guinea-pigs suggest that in some cases chlortetracycline may suppress rather than eradicate the Q fever agent.