Seroprevalence and associated risk factors of brucellosis, Rift Valley fever and Q fever among settled and mobile agro-pastoralist communities and their livestock in Chad.

Brucellosis, Rift Valley fever (RVF) and Q fever are zoonoses prevalent in many developing countries, causing a high burden on human and animal health. Only a few studies are available on these among agro-pastoralist communities and their livestock in Chad. The objective of our study was to estimate brucellosis, RVF and Q fever seroprevalence among Chadian agro-pastoralist communities and their livestock, and to investigate risk factors for seropositivity. We conducted a multi-stage cross-sectional serological survey in two rural health districts, Yao and Danamadji (966 human and 1041 livestock (cattle, sheep, goat and equine) samples)). The true seroprevalence were calculated applying a Bayesian framework to adjust for imperfect diagnostic test characteristics and accounting for clustering in the study design. Risk factors for each of the zoonotic diseases were estimated using mixed effects logistic regression models. The overall prevalence for brucellosis, Q fever and RVF combined for both regions was estimated at 0.2% [95% credibility Interval: 0–1.1], 49.1% [%CI: 38.9–58.8] and 28.1% [%CI: 23.4–33.3] in humans, and 0.3% [%CI: 0–1.5], 12.8% [%CI: 9.7–16.4] and 10.2% [%CI: 7.6–13.4] in animals. Risk factors correlating significantly with the respective disease seropositivity were sex for human brucellosis, sex and Q fever co-infection for animal brucellosis, age for human Q fever, species and brucellosis co-infection for animal Q fever, age and herd-level animal RVF seroprevalence within the same cluster for human RVF, and cluster-level human RVF seroprevalence within the same cluster for animal RVF. In Danamadji and Yao, Q fever and RVF are notably seroprevalent among agro-pastoralist human and animal communities, while brucellosis appears to have a low prevalence. Correlation between the seroprevalence between humans and animals living in the same communities was detected for RVF, highlighting the interlinkage of human and animal transmissible diseases and of their health, highlighting the importance of a One Health approach. Author summary: Infectious diseases transmitted between humans and animals, called zoonotic diseases, pose a global threat to human and animal health. Furthermore, diseased animals, especially livestock, can compromise the financial resources and livelihood of their owners as these depend on healthy animals for milk or meat production, or for agricultural work purposes. Brucellosis, Q fever and Rift Valley fever are two bacterial and one viral zoonotic disease that were found to be prevalent among many human-animal communities living in close contact, such as it is the case among Chadian agro-pastoralists. Limited data are available on the current status of these diseases in Chad. In this study, the authors investigated the prevalence of these three diseases among humans and their livestock (cattle, sheep, goats, horses and donkeys) by collecting blood samples and conducting serological analyses in two rural regions of Chad, Danamadji and Yao. Results point towards high Q fever and Rift Valley fever seroprevalences (13–49% and 10–28%, respectively), and low prevalence of brucellosis (< 1%), and towards a positive association between human and animal Rift Valley fever seroprevalence. With these findings, the study hopes to support current and future zoonotic disease surveillance and control efforts within the regions. [ABSTRACT FROM AUTHOR]