Prevalence and diagnosis of the etiologic agents of pyrexia of unknown origin in the Central Queensland Region

Pyrexia is an illness of unknown origin where people suffer unexplained fevers, headaches and fatigue. This study was undertaken to ascertain the prevalence of agents which may be associated with pyrexia in the Central Queensland region. Illnesses researched include Ross River Virus, Leptospirosis, Barmah Forest Virus, Brucellosis, Lyme Borrelosis and Streptococcal infections. A study was undertaken to ascertain the prevalence of agents which may be associated with pyrexia in the Central Queensland region. Five hundred and twenty four patient sera submitted to the laboratory from January 1991 to December 1992 for Ross River virus serology were also assayed by serological methods for evidence of exposure to Barmah Forest virus, flaviviruses, spotted fever group rickettsia, brucella, leptospirosis and lyme borrelosis. Titres of streptococcal antibodies and rheumatoid factor were also measured. Accompanying request forms were analysed for relevant clinical history and any additional pathology testing requests were noted. Ross River virus antibodies (IgG and/ or IgM) were found in 38.9% of patient sera. Males were significantly associated with the presence of antibodies (IgG and/or IgM) (P < 0.05) but females were 1.73 times as likely to have detectable IgM antibody at presentation. This suggests that females may be more symptomatic in the initial stages of infection and thus seek medical intervention. Flavivirus antibodies (IgG) were found in 19.79% of patient sera. One sample also contained IgM antibodies which reacted with both Kunjin and Alfuy viruses. Barmah Forest virus antibodies (IgG and/or IgM) were detected in 8% of patient sera. IgM antibody was detected in three patients, two of whom also had Ross River virus IgM antibody. Antibodies (IgG and/or IgM) to the spotted fever group of rickettsia were detected in 3.8% of patients. Lyme borrelosis antibodies (IgG) were detected in 1.7% of patients. A single case of brucellosis was diagnosed but no evidence of exposure to leptospiras was found. Raised streptococcal antibody titres were found in 27.1% of patient sera. Rheumatoid factor was detected in 4.696 of patient sera. A full blood count, erythrocyte sedimentation rate and rheumatoid factor determination were the most commonly requested additional pathology tests. Clinical history was provided on only 56.1% of request forms. These results have implications for future testing protocols. Diagnostic problems associated with serological testing on single serum samples were noted.