Molecular detection of Ehrlichia ruminantium and Coxiella burnetii among apparently healthy sheep and goats in eastern Tanzania.

Abstract

Heartwater and Coxiellosis caused by Ehrlichia ruminantium and Coxiella burnetii, respectively are among the common tick-borne diseases (TBDs) of small ruminants in many regions of the world. Coxiella burnetii is also zoonotic, presenting a concern for public health. Despite their economic importance in the livestock sector in Sub-Saharan Africa, little attention has been given to these pathogens of sheep and goats. This cross-sectional study aimed at establishing the infection rates of Coxiella burnetii and Ehrlichia ruminantium in clinically healthy sheep and goats from Chalinze and Muheza districts in Tanzania. The PCR results revealed that of 223 animals sampled, (31.8%, n = 71) were positive for at least one pathogen. The most frequently observed pathogen was C. burnetii (16.1%, n = 36), followed by E. ruminantium (12.6%, n = 28) and their co-infections (3.1%, n = 7). The prevalence of these TBPs differed significantly (p = 0.020) among sheep (27.9%, n = 17) and goats (34.1%, n = 57). The prevalence of C. burnetii was (11.5%, n = 7) in sheep and (17.9%, n = 29) in goats. On the other hand, the prevalence of E. ruminantium was (9.8%, n = 6) for sheep and (13.2%, n = 22) for goats. The co-infection of C. burnetii and E. ruminantium differed significantly (p < 0.001) among small ruminants. Only the prevalence of C. burnetii increased significantly (p = 0.038) with increasing age. The observation of DNAs of TBPs in apparently healthy sheep/goats suggests that these animals have either established a state of enzootic stability against the pathogen or infection was by non-pathogenic variants of the pathogen. Such animals continuously act as sources of infection for ticks and other hosts, including humans, hence facilitating the transmission and maintenance of the pathogen in an area. It is thus essential to continue monitoring these pathogens regardless of the clinical status of the small ruminants.