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Experimental Leptospira borgpetersenii serovar hardjo infection of pregnant cattle
C R Smith1, M R McGowan, C S McClintock
1Dayboro Veterinary Surgery, School of Veterinary Science, University of Queensland.
Objective:
To observe the effect upon the foetus of experimental infection of pregnant cattle with Leptospira borgpetersenii serovar hardjo.
Design:
A disease transmission study using pregnant cattle.
Procedure:
Fourteen heifers serologically negative to L hardjo were artificially inseminated and later challenged with a north-Queensland isolate of L hardjo by conjunctival inoculation. The heifers were serologically monitored and their urine examined for the presence of leptospires using culture and fluorescent-antibody tests at appropriate intervals. Elective caesarean sections were performed on pregnant heifers at 6.5 weeks after the challenge. Foetuses were examined using serological, histopathological, microbiological and fluorescent-antibody tests.
Results:
Ten of the heifers became pregnant, but three subsequently aborted before challenge. After challenge, all 14 heifers seroconverted and L hardjo was isolated from the urine of 6 of the 7 pregnant heifers. No evidence of foetal L hardjo infection was detected. Two of the foetuses had histopatho-logical lesions consistent with Neospora sp infection.
Conclusion:
It is likely that the isolate of L hardjo used in this study does not normally infect the foetus. Neospora sp may be a more significant cause of bovine reproductive wastage.