Epidemiology, risk factors and vector density of trypanosomosis in cattle in Ethiopia: Systematic review and meta-analysis

Background

Bovine trypanosomosis remains a major barrier to livestock productivity, agricultural progress, and socioeconomic development in Ethiopia's large tsetse belt regions, threatening 70 million cattle. Therefore, this review examined published literature from the last ten years to estimate the pooled prevalence, risk factors, and vector density of bovine trypanosomosis. This systematic review followed the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guidelines, using PubMed, Web of Science, HINARI, Google, and Google Scholar. Pooled prevalence and risk factors were calculated with a random effects model in R software, with a 95 % confidence interval. This meta-analysis included research published after 2015 on trypanosomosis in Ethiopian cattle, where Trypanosoma was classified at least to the genus level. Studies on other species, lacking specific prevalence data and published before 2015 were excluded.

Results

A total of 26 articles were included in this meta-analysis. The overall pooled proportion of bovine Trypanosomosis cases was 9 % (95 % CI: 8–9 %). Considerable heterogeneity was observed across the included studies (I² = 94 %; P < 0.01). The highest pooled prevalence of trypanosomosis was reported in Amhara and Oromia (8 %), followed by Benishangul Gumuz (BSGR) (7 %). Based on the subspecies analysis, the highest pooled proportion was 65 % (95 % CI: 58 %–71 %) for T. congolense (I² = 81 %: p = 0.01), followed by 32 % for T. vivax (I² = 60 %: P = 0.61) and 19 % for T. brucei (95 % CI: 7 %–41 %). Among the risk factors, poor body condition, black coat color, and packed cell volume (PCV) were found to be significant for the development of this disease. Black-coated animals were 2.36 and 3.48 times more susceptible to trypanosomosis than red- and white-coated animals, respectively. According to the pooled odds ratio, animals in poor body condition were 2.82 times more likely to have bovine trypanosomosis. Animals infected with Trypanosoma were 18 times more likely to have a lower packed cell volume (PCV) compared to non-infected animals. The study found that Tsetse flies were responsible for 72.32 % of bovine trypanosomosis cases, with Glossina pallidipes and Glossina tachinoides being the most common species. The remaining 27.68 % were due to other biting insects. The study highlights the need for science-based risk mitigation strategies to control Trypanosoma infections, emphasizing the crucial role of Tsetse flies, particularly G. pallidipes and G. tachinoides, in transmission.