The epidemiology of Brucellosis and Q fever in a cross-sectional serosurvey of occupationally exposed groups in peri-urban Lomé, Togo

Background

Brucella species and Coxiella burnetii have been detected in livestock populations in Togo. Populations exposed to livestock ruminants through 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. 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 from farms were tested using an indirect milk ELISA for Brucella IgG.

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 (39.2%, 95% CI 26.6 - 53.4%).

Farmworkers had nearly twice the odds of being Brucella seropositive compared to abattoir workers (OR 1.93, 95% CI: 0.94-3.93, p=0.07). In farmworkers, working on farms with animal ill health, a positive milk test, participating in small animal husbandry and assisting with cattle abortion were all associated with increased odds of seropositivity. Workers who consumed unboiled milk at least every month were more likely to be seropositive (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 Lome have been exposed to both Brucella and Coxiella burnetiid bacteria. The widespread consumption of unboiled dairy products and lack of 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.

Author summary

Human and animal health are inextricably linked, particularly for those who live and work closely with animals. Brucellosis and Q fever are two zoonotic diseases transmitted through animal contact and dairy product consumption, which cause non-specific fevers and for which diagnostic tests are lacking in many LMIC contexts. Previous studies have shown that both bacteria circulate in livestock in Togo. We undertook a survey in dairy farm and abattoir workers in peri-urban Lomé, Togo, and found that 9.5% and 28% of workers were seropositive for Brucella and C.burnetii respectively. We found that risk factors included animal husbandry practices and consumption of dairy products. Mitigating practices such as the use of PPE and boiling milk are simple ways that livestock workers could protect themselves from these and other zoonotic disease.