Epidemiologic study of q fever in smallholder dairy cattle in selected regions of Tanzania

Abstract

A cross-sectional study was conducted to determine prevalence and the risk factors associated with Coxiella burnetii seropositivity in smallholder dairy cattle in six regions from the southern highland and northern zones of Tanzania between July 2019 and October 2020. A total of 2049 blood samples and 1920 vaginal swabs were collected from dairy cattle. Serum was tested for antibodies against C. burnetii using an indirect enzyme-linked immunosorbent assay (ELISA). C. burnetii DNA was identified from vaginal swabs using quantitative polymerase chain reaction (qPCR) analyses. A questionnaire survey was designed and uploaded to the Open Data Kit (ODK) cloud platformsoftware version 1.22.4. At each household, the cattle owner aging equal or over 18 years was interviewed to understand the risk factors related to animal health, husbandry, and farmer socioeconomics, as well as environmental variables. C. burnetii prevalence was calculated at different epidemiological levels and maps were created to visualize Q fever spatial distribution. Logistic generalized linear mixed effects models were built to explorethe association between ELISA binomial results, and a set of risk factors and environmental variables important for C. burnetii occurrence. An overall animal seroprevalence of 3.86% (79, 2049) 95% CI 3.06 - 4.78 was estimated across the study regions. Among these regions, Tanga (northern zone) and Iringa (southern zone) showed the highest prevalence with 8.21% (95% CI 6.0 - 10.89%) and 4.63% (95% CI: 2.49 - 7.78%) respectively. On the other hand, molecular identification of C. burnetii from vaginal swabs of selected cows revealed an overall prevalence of 0.94% (18,1920) (95% CI 0.5-1.4%). Among the northern zone regions, Arusha had the highest of 2.3%(95%CI 0.9-4.7%) and on the southern highlands zone, Iringa emanated to have the highest prevalence of 0.73% (95%CI 0.08-2.5%). Animal age, extensive feeding system, and temperature were univariably significant risk factors to C. burnetii seropositivity. The final multivariable logistic regression model showed that old animal age, extensive feeding system, and low precipitation were strongly associated with Q fever seropositivity. These findings indicate that C. burnetii circulates among smallholder dairy cattle across regions in Tanzania. However, Tanga, Arusha and Iringa are the three regions with the highest seroprevalence and should be considered for systematic and active surveillance. Furthermore, “One Health” approaches are necessary to fully understand disease transmission and control of this zoonotic disease.