Seroprevalence and potential risk factors of brucellosis in sheep from America, Africa and Asia regions: A systematic review and meta-analysis

Brucellosis, a neglected and global zoonotic disease, infect a variety of mammals, among which sheep are one of the main hosts. This disease results in huge economic losses and is a widespread concern around the world. Based on the selection criteria, 40 articles from 2010 to 2021 of five databases (CNKI, Wanfang, VIP, PubMed and Science Direct) reported in America, Africa and Asia were included. The data showed that during this period, the overall seroprevalence of sheep brucellosis on these three continents was 6.2%. At the regional level, sheep brucellosis had the highest seroprevalence (8.5%) in Africa and the lowest seroprevalence (1.9%) in the Americas. With regard to the age of the sheep, the seroprevalence was significantly higher in adult sheep (15.5%) than in lambs (8.6%). Further, the seroprevalence was significantly higher in sheep that had abortion (44.3%) than in pregnant (13.0%) and non-pregnant sheep (9.5%). With regard to herd size, herds with >20 sheep (35.4%) had a significantly higher seroprevalence than herds with <20 sheep (16.8%). In terms of farming and grazing mode, free-range rearing (8.4%) was associated with a significantly higher seroprevalence than intensive farming (2.8%), and mixed grazing (37.0%) was associated with a significantly higher seroprevalence than single grazing (5.7%). Sheep brucellosis is widely distributed in sheep-rearing regions of America, Africa and Asia, and sheep are susceptible to brucellosis by themselves or from other infectious sources. Therefore, timely monitoring of ovine brucellosis and improving farming and grazing patterns are critical to reducing the prevalence of brucellosis.