Serological titres to Leptospira fainei serovar hurstbridge in human sera in Australia

A set of 723 diagnostic sera from human patients, submitted for the microscopic agglutination test (MAT) for antibodies to a group of 6 leptospiral serovars, was also tested by MAT for antibodies to the recently-discovered Leptospira fainei serovar hurstbridge. MAT titres of greater than or equal to 128 to serovar hurstbridge were detected in 13.4 % of these sera, and titres of greater than or equal to 512 in 7.2 %. In contrast, none of 62 sera obtained from a control population of laboratory staff gave titres of greater than or equal to 128. The difference between the number of titres of greater than or equal to 128 given by the two groups of sera was highly significant (P < 0.01). The titres observed may have been due to cross-reactions with other leptospiral serovars, but this could not be demonstrated. An alternative explanation is that serovar hurstbridge is present in the human population.