Survey of rickettsial antibodies at two local sites and review of rickettsiosis in Papua New Guinea.

The status of rickettsial infection in Papua New Guinea (PNG) is unknown although several reports of typhus-like illnesses infecting predominantly white settlers and the Allied troops during World War 2 were published between 1930 and 1945. We performed a serological survey for evidence of rickettsial infection by measuring rickettsia-specific antibody levels in the blood of 191 non-randomly selected Papua New Guineans living in Port Moresby (n=93) and in the highland villages of Samberigi (n=98). Antibodies were measured by a microimmunofluorescence method using a panel of rickettsial antigens of a number of species and strains. In addition, we have reviewed the current status of rickettsiosis in PNG. Overall, we were able to demonstrate significant titres of antibodies to two groups of rickettsiae, the scrub typhus group (STG) and the spotted fever group (SFG). All positive individuals (7/191) were residents of Port Moresby. None from the highlands showed any significant levels of antibodies to rickettsiae. The strains detected within each group were Gilliam and Karp for STG and, for SFG, Rickettsia honei, R. conorii, R. sibirica, R. rickettsii, R. australis and R. akari. No significant antibody titres to typhus group infection were detected in either Port Moresby or highland volunteers. These findings were not surprising given previous reports of typhus-like illnesses and favourable environmental characteristics for rickettsiae in some parts of PNG. Until a definite status of this disease is known, we suggest that rickettsial infection be included as a differential diagnosis for patients presenting with acute febrile illness in Port Moresby and surrounding areas.