Serological studies and isolations of serotype hardjo and Leptospira biflexa strains from horses of Argentina

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Abstract
Three pathogenic leptospiras and 12 saprophytic L. biflexa strains were isolated from 72 apparently normal horse kidneys collected at an abattoir in Argentina. Cross-agglutination reaction patterns of the pathogens showed that they were antigenically homologous with members of the L. hebdomadis group. When 1 strain was compared to L. hebdomadis serotypes in reciprocal agglutination-absorption tests, it was serologically homologous to seotype L. hardjo. This is the 1st known report of an isolation of this serotype from horses. Serological tests were also carried out on randomly collected abattoir sera from 245 horses to determine the prevalence of equine leptospirosis. Significant antibody titers (1:100 or greater) were found in 74.6% of the sera. Predominant reactions occurred with the L. pomona, L. hebdomadis group, L. pyrogenes, L. tarassovi, and L. canicola antigens. Agglutination tests performed with antigen prepared with 1 saprophytic L. biflexa isolate showed seropositive reactions in 99.1% of the equine sera, with agglutination titers from 1:100-1:3200. Absorption of selected horse sera with the saprophytic strain removed the agglutinins to L. interrogans serotypes. This suggests the possibility that L. biflexa strains may act as an antigenic stimulus and account for some of the persistent multiple cross-reaction patterns of equine sera with pathogenic serotypes. [Horses may be an important reservoir for transmitting leptospirosis to animals or man.].