High prevalence of Q fever among patients clinically diagnosed with brucellosis in a Kenyan pastoralist community.

Coxiella burnetii is a zoonotic bacterial agent responsible for Q fever in both humans and animals. Ruminants are the most common livestock species associated with Q fever infections in humans. The disease presentation in humans range from asymptomatic, non-specific symptoms to fatal illness. In Kenya, no healthcare indicators seek to clinically diagnose and report Q fever because there are no readily available diagnostic technologies. We conducted a prospective observational study with paired serological sampling leveraging on the existing equipment in the Kajiado County referral laboratory to demonstrate antibodies to Coxiella burnetii in sera of febrile patients presenting with Brucella-like symptoms using the indirect immunofluorescent assay (IFA) and a fluorescent microscope provided for diagnosis of tuberculosis. A total of 100 paired blood samples were obtained from consenting and assenting study subjects. A pilot-tested questionnaire was used to collect patient's socio-demographic information, knowledge of Q fever disease, and community practices that put them at risk of exposure. Coxiella burnetii phase I (IgG) and phase II (IgM) antibodies were characterized, while Brucella spp. IgG antibodies were demonstrated using an indirect enzyme-linked immunosorbent assay (iELISA) and febrile Brucella agglutination test (FBAT). The overall seroprevalence of C. burnetii IgG and IgM antibodies was 49% and 27%, respectively, compared to only 13% reactivity with Brucella ELISA. Q fever prevalence substantially exceeded that of brucellosis in patients presenting with brucellosis-like symptoms in this pastoral community, suggesting a substantial burden of undiagnosed Q fever.