Spatial risk assessment of ovine Scrapie in Brazil

Abstract

Brazilian sheep farming is an ancient socioeconomic activity of great importance for maintaining income and generating family employment. Brazil is the largest producer of sheep in South America, making it a strategic country for the control of infectious diseases such as scrapie. In the present study, scrapie was officially reported in 74 cases in nine Brazilian states between 2005 and 2021. Among all Brazilian regions, the South with 54.06 % (40/74), the Midwest with 28.38 % (21/74), and the Southeast with 16.21 % (12/74) stood out with higher relative frequencies in the number of cases of the disease. Among the states, Santa Catarina presented 35.14 % of the notified cases, and the risk of incidence (IR) was 91.9 per 100,000 sheep. The years with the highest reported cases were 2012 (17 cases and IR = 2.11) and 2017 (16 cases and IR = 6.17). There was the formation of a primary cluster in the year 2017, formed only by the state of Santa Catarina, with relative risk (RRs) = 313.97, and a secondary cluster formed by the states of Mato Grosso, Mato Grosso do Sul, Goiás, Tocantins, Minas Gerais, and São Paulo in the period from 2006 to 2009, with RRs = 27.92. All of the states with reported cases shared borders, demonstrating the disease's ability to spread across state lines. Scrapie must be prevented from spreading in Brazil by implementing active surveillance measures.