Seroprevalence and risk factors for Brucella species and Coxiella burnetii exposure in a cross-sectional serosurvey of occupationally exposed groups in peri-urban Lomé, Togo

Abstract

BACKGROUND: Brucella species and Coxiella burnetii have been detected in livestock populations in Togo. Populations exposed to livestock ruminants through their occupation may be at increased risk of infection. METHODS/PRINCIPAL FINDINGS: A cross-sectional serosurvey was conducted in 108 abattoir and 81 dairy farm workers (from 52 dairy farms) in peri-urban Lomé, Togo in 2019-2020. Structured questionnaires were used to collect data on participant livestock contact and dairy product consumption. Sera were tested using the Rose Bengal plate agglutination test (RBT) and the indirect Brucella IgG Enzyme-Linked Immunosorbent Assay (ELISA) for Brucella, and the IgG ELISA for Coxiella burnetii in Phase 1 and in Phase 2. Fresh bulk milk samples from farms were tested using an indirect milk ELISA for Brucella IgG. The association between seropositivity and exposure variables was examined using logistic regression with robust standard errors to account for site-level clustering. Eighteen workers (9.5%, 95% CI 5.5-16.0) were Brucella seropositive. Twenty-eight percent (95% CI 22.5-34.3) of workers were seropositive for C. burnetii. Twenty of fifty-one farms which gave milk samples tested positive for Brucella antibodies (39.2%, 95% CI 26.6 - 53.4%). Farmworkers had nearly twice the crude odds of being Brucella seropositive compared to abattoir workers (OR 1.93, 95% CI: 0.94-3.93, p = 0.07). After adjusting for age, working on farms with animal ill health, a positive milk test, participating in small ruminant husbandry and assisting with cattle abortion were all associated with increased odds of seropositivity. Farm and abattoir workers who consumed raw milk at least every month were more likely to be seropositive for Brucella species (OR 3.79, 95% CI: 2.34-6.13, p < 0.001) while participants who consumed fermented milk and cheese had greater odds of being seropositive for C. burnetii (OR 1.59, 95% CI: 1.26-2.00, p < 0.001 and OR 1.70, 95% CI: 0.97-2.98, p = 0.07 respectively). CONCLUSIONS: Livestock workers in peri-urban Lomé have been exposed to both Brucella and Coxiella burnetii bacteria. The widespread consumption of raw dairy products and lack of personal protective equipment (PPE) use is of concern as both dairy consumption and participation in animal husbandry activities have been seen to increase odds of seropositivity for both pathogens. A One Health prioritization of zoonotic disease would help to bring together the relevant sectors to adequately resource prevention and control of zoonoses of public health concern in Togo, which may particularly impact workers in close contact with animals.