Bovine Ehrlichiosis Prevalence: A Systematic Review and Meta-Analysis of Molecular Studies

While some Ehrlichia species, such as E. ruminantium and E. minasensis, are not popular even among veterinarians, they can infect cattle. The current study aimed to review studies on Ehrlichia spp. to evaluate its worldwide molecular prevalence, given the lack of information about bovine ehrlichiosis and the lack of previous systematic reviews and meta-analyses on this subject. In order to determine the molecular prevalence of Ehrlichia spp. in cattle, a systematic review of the literature was conducted in three databases. A meta-analysis with a random-effects model was performed to calculate the pooled prevalence with 95% confidence intervals (95% CI) and measures of heterogeneity were reported. Subgroup analyses were performed in terms of Ehrlichia species, country, and regions. The literature search yielded 1051 papers until August 1, 2019, with 71 studies entirely eligible for review. The pooled molecular prevalence for Ehrlichia at the individual level (N = 6232) was 2.3% (95% CI: 1.7-2.9%) with the highest value of 82.4%. Studies identified the highest pooled molecular prevalence of 6.6% (95% CI: 0.6–12.7%) for E. canis, followed by E. ruminantium (n = 4695, 75.33%) 52 studies, with 1.7% (95% CI: 1.1–2.3%) and E. chaffeensis with 1.5% (95% CI: 0.0–0.3%). Moreover, the obtained result was indicative of only one study addressing E. minasensis. As the findings suggested, heartwater (E. ruminantium infection) is a notifiable disease of domestic and wild ruminants, recorded by the World Organization for Animal Health. There is a possible risk of endemic heartwater in the Americas due to the climatic features. Furthermore, E. minasensis, E. chaffeensis, and E. canis were observed in cattle although the two last species could be a molecular misidentification with regard to their phylogenetic relationships with E. minasensis.