Leptospirosis—Induced abortion

Abstract

History and Clinical Signs : Icterus, anemia and fever may accompany or precede the abortion. Most frequently there are no easily detected clinical signs of infection of the dam preceding abortion. Gross Lesions : No gross lesions occur consistently in fetuses aborted due to leptospirosis. The fetus may be expelled soon after its death or 24 to 48 hours after death. Occasionally calves from infected dams may be born alive, but weak and often die within hours. Microscopic Lesions : No microscopic lesions occur consistently in the fetal tissue. Cultural Procedures : Isolation of leptospires from the tissues of the aborted bovine fetus is rarely possible. Isolation of leptospires from the urine of the cow within a week to 10 days after abortion is frequently possible. This provides absolute evidence of infection and presumptive evidence of the cause of the abortion. Serologic Procedures : A single positive microscopic agglutination test (MA) with a titer 1:100 or greater does not distinguish between infected and recovered animals. A four (4) fold or greater rise in titer in paired serum samples, one taken soon after abortion and the other 7 to 10 days later, is reasonable evidence of an active infection and presumptive evidence of the cause of the abortion. The lack of a titer rise in paired serum samples does not rule out leptospirosis as the cause of the abortion. Special Procedures : Demonstration of leptospires in fetal tissue or placenta by Levaditi's Warthin Starry stain, or fluorescent antibody (FA) technique is desirable, but seldom successful. Preferred Diagnostic Methods : 1. 1. Isolation of leptospires from, or demonstration of them in, the tissues of the aborted fetus or its placenta. 2. 2. Isolation of leptospires from, or demonstration of them in, the urine of the aborting dam within about 2 weeks after abortion. 3. 3. Demonstration of 4 fold or greater increase in MA antibody titer to a leptospiral serotype in the second of 2 blood samples from the aborting dam, one sample taken near the time of abortion and the other 7–10 days later. Failure to demonstrate a rising titer does not rule out leptospirosis as the cause of the abortion. Occasionally an infected animal will not develop a demonstrable titer.