Geographical and temporal spread of equine rabies in Brazil

Abstract

In Brazil, the horse is frequently used in cultural activities, sports, and in rural and urban work, implementing the economy in different social classes. Among the diseases in horses with zoonotic potential, rabies has been neglected in the country, increasing the risk of spreading the disease across borders. The present study evaluated the spatiotemporal distribution and temporal trend of rabies in horses in Brazil between 2010 and 2019. During this period, 1290 cases of rabies were detected in horses in Brazil, mainly in the states of São Paulo (21.7%) and Mato Grosso (13.3%). However, Espírito Santo stood out, with an incidence risk (IR) of 139.7 cases of rabies per 100,000 horses. The years 2013 and 2017 had higher peaks of IR for the disease, and the states that contributed to this increase were Mato Grosso, São Paulo, and Espírito Santo. There was no monthly seasonality of the disease among the states. The temporal trend revealed an increase for the northeastern region (Annual Percentage Change [APC]: 8.9%) and for Alagoas State (APC: 26.6%). In the spatiotemporal analysis, three high-risk clusters were formed: (i) cluster A (Relative Risk [RRs]: 6.21), involving only Minas Gerais, between 2017 and 2019; (ii) cluster B (RRs: 6.18), involving only Mato Grosso, between 2011 and 2013; and (iii) cluster C (RRs:4.71), involving the states of Rio de Janeiro and Espírito Santo, between 2010 and 2014. Only the states of Roraima and Amapá had no cases of equine rabies during the study period. Therefore, rabies in horses occurs in all Brazilian regions, with areas at high risk of infection concentrated in the Southeast. However, attention should be directed to the north-eastern and northern states, where notifications were infrequent, with an unknown risk in relation to the spread of rabies to transboundary regions. This is the first study evaluating the interstate distribution of rabies in equine species in regions of Brazil.

Keywords: Horse; Rabies; Risk; Spatiotemporal analysis; Trends.