Abstract

Members of the genus Rickettsia have garnered much attention worldwide in recent years with the emergence of newly recognized rickettsioses. In New Zealand, only Rickettsia typhi and R. felis, belonging to the typhus and spotted fever groups, respectively, have so far been found (1). R. typhi, primarily transmitted by the oriental rat flea (Xenopsylla cheopis), has a worldwide distribution and causes murine typhus in humans (2). At the end of 2009, a total of 47 cases of murine typhus had been recorded in New Zealand. In contrast, although the cat flea (Ctenocephalides felis) can carry R. felis in New Zealand (3), no human infections have been reported. However, because R. felis shares a similar clinical profile to murine typhus, infection can be mistaken for a suspected case of R. typhi (4). Clinical suspicion of rickettsial infection is widely confirmed by serologic tests with the indirect immunofluorescence assay (IFA) being the standard test. However, antibodies against R. felis in human sera are known to cross-react with R. typhi in IFA (5). Western blot (WB) and crossadsorption assays, in combination with IFA, can differentiate between several rickettsioses (5, 6). We report on the trial in New Zealand of WB and crossadsorption assays for differentiating retrospectively between past R. typhi and R. felis infections and evidence of R. felis infection in persons living in the country.

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