Sero-epidemiology of Coxiella burnetii in livestock and humans in Isiolo county Kenya

TL;DR

This study found high rates of Coxiella burnetii exposure in both livestock and humans in Kenya, identifying key risk factors and the need for targeted public health interventions.

Contribution

The study provides the first linked human-livestock sero-epidemiological data on Coxiella burnetii in Isiolo County, Kenya.

Findings

Coxiella burnetii seroprevalence was 47.9% in livestock and 44.7% in humans.

Goats had higher odds of exposure compared to other livestock species.

Human exposure was associated with being female and living in a household with seropositive animals.

Abstract

Coxiella burnetii, the causative agent of Q fever, is a globally distributed pathogen with significant zoonotic and economic impacts, particularly in regions where humans and livestock interact closely. Although endemic in many countries, including Kenya, comprehensive epidemiological data on the pathogen are limited. To address this gap, we conducted a linked human and livestock populations study in Garbatulla, Isiolo County to assess seroprevalence and identify potential predictors of C. burnetii exposure.

We used a cross-sectional design with multistage sampling. Blood and serum samples were collected from 2,157 livestock and 683 humans that were recruited from 242 households. Additional data on herd/household and subject characteristics were collected using a structured questionnaire. Indirect enzyme-linked immunosorbent assay (ELISA) was used to test the serum samples for antibodies against C. burnetii. Univariable and multivariable analyses identified potential predictors of exposure in both livestock and humans.

The overall seroprevalence of C. burnetii was 47.9% (95% CI: 45.7%-50.1%) in livestock and 44.7% (95% CI: 40.9%-48.5%) in humans. In livestock, significant variation in seroprevalence was found by species (p < 0.001). Goats were found to have significantly higher odds of being exposed to C. burnetii compared to cattle, sheep and camels. Both weaners and young animals had significantly lower odds of exposure compared to adults. In humans, the odds of C. burnetii exposure were lower among females compared to males. Herds seropositivity was also an important predictor of humans exposure to C. burnetii.

This study provides evidence of high seroprevalence of C. burnetii in both livestock and humans, highlighting the need for active surveillance programs targeting both populations. These programs should focus on identifying active shedding and implementing targeted control measures to mitigate the public health risks associated with C. burnetii.

Coxiella burnetii is an important zoonotic pathogen in Kenya that causes illness in humans and livestock in many rural pastoral settings. We conducted a linked human-livestock study to investigate the seroprevalence of C. burnetii. We also identified risk factors associated with C. burnetii seropositivity. Our study found a high seroprevalence in humans and animals and identified significant risk factors associated with exposure. In livestock, the risk factors included goats and being older. In humans, significant risk factors included being female and residing in a household that had seropositive animals. Implementation of interventions such as targeted awareness campaigns about the disease, species-specific interventions, and promoting safe livestock management practices can potentially reduce the pathogen transmission in livestock and spill over to humans. Future studies should examine the role of wildlife in the transmission of C. burnetii and the efficacy of the measures that reduce the risk of transmission.

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