Tuberculosis in small ruminants and dromedary camels in Ethiopia: A systematic review and meta-analysis

Tuberculosis (TB) is a chronic infectious disease of livestock with serious economic and public health impact in Ethiopia. The disease is reported from cattle, small ruminants and dromedary camels in the country. However, there is no organized summary report on the magnitude and distribution pattern of TB in small ruminants and dromedary camels, unlike that of bovine TB. Consequent to this gap, this review was organized to provide pooled prevalence estimates, and examine level of heterogeneity among studies at national level. In addition, it attempts to illustrate the spatial distribution patterns along the three livestock species based on available reports. Tuberculosis articles on the aforesaid livestock species were searched online using PubMed, CAB direct, Web of Science and AJOL databases. Eighteen articles published from January 2000 to May 15, 2020, written in the English language that fulfill the selection quality criteria were considered for the review. Altogether, 50 district based observational studies conducted on 10,371 goats, 6262 dromedary camels, and 1457 sheep were used for analysis. Accordingly, the pooled prevalence estimates of TB, in a random effect model were 2.3 % (95 % CI: 1.7, 3.1) for goats, 0.8 % (95 % CI: 0.5, 1.4) for sheep and 8.2 % (95 % CI: 6.6, 10.2) for dromedary camels. The subgroup analysis revealed presence of statistically significant differences (p < 0.001) in pooled prevalence estimates among the three species. In multivariable meta-regression model, diagnostic methods used for screening (single intra-dermal comparative cervical tuberculin test (SICCTT)> 2mm, SICCTT > 4mm and detailed postmortem inspection) were the only predictors identified to show statistically significant difference (p<0.001) and explained 68.6 % of the explainable heterogeneity (R² =0.686) in goat TB studies. In general, study reports on small ruminant and dromedary camel TB are limited throughout the country. The most significant data gaps were in Gambella, and Benshangul-Gumuz regional states, where no single report could be retrieved on small ruminant TB. Limitation of study reports and lack of comparable categories constrained further investigation on other predictors in sheep and camel studies. Thus, the authors would like to emphasize the need for more representative studies in the species of concern in all regions of the country. Meanwhile, the relatively higher proportion of TB in dromedary camels demands special attention in arid and semiarid parts of the country, as it is the leading livestock species on which agropastoralist and pastoralists livelihoods depend.