Impact of herd mobility on brucellosis seroprevalence and spread risk resulting from cross-border transhumance

BackgroundCross-border livestock mobility through transhumance is mainly practiced in West African countries for seasonal access to resources and market. Cross-border herds are involved in the dynamic of transboundary animal diseases among them brucellosis taken as model. Brucellosis is a zoonotic disease causing abortion.ObjectivesThis study explores the seroprevalence of brucellosis according to mobility and infection spread between Mali and Cote d'Ivoire in the context of seasonal cross-border transhumance.MethodsFrom February to April 2021, a transversal serological survey of brucellosis was conducted on 521 cattle from 111 transhumant herds and 283 cattle from 59 sedentary herds, all from Mali.ResultsThe global individual seroprevalence for Brucella spp. in transhumant and sedentary cattle from Mali was 8.2% (95% CI = 6.0-10.5). At herd level, seroprevalence was 21.2% with a significant variation between transhumant (11.7%) and sedentary (39.0%) herds. For herds in transhumance, cattle seropositivity was associated with a previous infection suspected by herdsmen odds ratio (OR = 4.4; 95% CI = 1.1-18.1) and unknown abortion aetiology (OR = 4.3; 95% CI = 1.0-17.3). The departure region (coming from Sikasso) and previous brucellosis infection or unexplained abortion could be used to predict Brucella infection in transhumant herds with a probability of around 60%. The risk of brucellosis introduction in host regions was high despite the individual animal seroprevalence of 3.6% and a low sale rate in transhumant cattle.ConclusionsThe findings suggest that testing transhumant during border control and survey of cattle markets and sales could improve risk control of the spread of disease at regional scale. This study aims to explore the seroprevalence of brucellosis according to mobility, and the infection spread between Mali and Cote d'Ivoire in the context of cross-border seasonal transhumance. Herd-level brucellosis seroprevalence was significantly higher in sedentary herds (39.0% of herds) than in transhumant herds (11.7%) in Mali. The risk of brucellosis spreading to host regions was between 70% and 90%, and resulted from 3.6% individual seroprevalence in transhumant cattle, with 0.3%-0.6% of transhumant cattle sold. image