Leptospirosis in Rodents and Mongooses on the Island of Hawaii

Abstract

Summary Evidence is presented of high leptospiral carrier rates in Rattus norvegicus and Mus musculus trapped on the Island of Hawaii. A high incidence of culture-positive, seronegative rodents is reported and possible explanations are offered in terms of balance between host and leptospiral factors. Isolations of Leptospira canicola and L. sejroe from the mongoose (Herpestes auropunctatus), of L. australis from R. norvegicus, and of L. sejroe in the Western Hemisphere are reported for the first time. L. icterohemorrhagiae, the predominant serotype, was isolated from rodents having higher blood agglutination titers to other leptospiral serotypes; this is attributed either to infection with a second serotype or to the so-called “paradoxical reaction.” Male R. norvegicus and R. rattus had slightly higher leptospiral infection rates than did the females; male R. exulans were infected more than twice as often as were females; and older rats of all species were infected more than three times as often as were juveniles.