Brucellosis serology as an alternative diagnostic test for patients with malaria-like symptoms

Background: In a low transmission zone for malaria, we explored the presence of brucellosis as an alternative diagnosis in febrile patients. Specifically, the objective of our study was to determine the proportion of patients presenting to the hospital with malaria-like febrile symptoms that were concurrently brucellosis seropositive, and assess related risk factors.
Methods: The study was done at the rural hospital in Endulen, in the Ngorongoro Conservation Area (NCA), Tanzania. Hospital patients were enrolled showing malaria-like febrile symptoms and were tested for malaria (microscopy) as well as brucellosis (agglutination test, plus commercial ELISAs for IgM and for IgG). Patient demographic characteristics and risk factors for brucellosis were determined using a questionnaire interview.
Results: A total of 159 patients were enrolled, of which 57 were positive for malaria and 58 were positive by ELISA for brucellosis, with 54 (93%) of these brucellosis-positives solely positive for isotype IgG, 1 (1.7%) solely for isotype IgM, and 3 (5.2%) positive for both IgM and IgG. However, the brucellosis agglutination test was only positive in 9 of 159 samples. Co-infections of malaria and brucellosis occurred, but malaria disease status was not significantly correlated with brucellosis status. Patients serologically positive for brucellosis were more likely to have had contact with aborted animal materials (p=0.002).
Conclusions: Brucellosis is a potentially missed diagnosis amongst pastoralists in rural Tanzania with malarialike symptoms. However, concurrent and isotope-specific serology is integral to ensure detection and appropriate clinical management.