Seroprevalence and risk factors of Coxiella burnetii (Q fever) infection among humans in Bura irrigation scheme, Tana River County, Kenya

Background: Coxiellosis (Q fever) is a zoonotic disease caused by the bacterium Coxiella burnetii. The bacteria is commonly found in various livestock and wildlife species such as cattle, sheep, goats, pigs, rodents, birds, dogs, cats, etc. In this study, we sought to estimate the prevalence of Coxiella burnetii IgG antibodies among humans and to identify risk factors for exposure.
Methodology: Blood samples were collected from a total of 272 randomly selected subjects in Bura irrigation scheme and manyattas around the scheme. Serum were prepared from these samples in the study sites and transported to Nairobi for analysis. Screening was done using a commercial ELISA antibody test kit (SERION ELISA classic Coxiella burnetii Phase 1 IgG) for the detection of human antibodies in serum directed against Coxiella burnetii Phase 1.
Results: The seroprevalence of coxiella burnetii in humans was 26.8%. This was higher in subjects sampled in the irrigation scheme (30.2% [95% CI]) relative to those sampled in the non-irrigated areas (16.4% [95% CI]). The seroprevalence for CB among adults, children and adolescents was 34.2% (95% CI), 26.8% (95% CI) and 23.2% (95% CI), respectively. There were marginal differences in the seroprevalence of Coxiella burnetii between males and females; these were estimated to be 28% and 26%, respectively. Risk factors associated with seropositivity in univariate analysis included occupation and age.
Conclusion: Farmers have a high level of exposure to Coxiella burnetii compared to pastoralists. This is an unexpected observation and more analyses are being done to determine potential routes of exposure.