Prevalence of equine infectious anemia in stud farms in Minas Gerais, Brazil

Horse breeding is expanding in Brazil. Nevertheless, equine infectious anemia (EIA) a transmissible, incurable disease is an obstacle to the development of the horse industry. Therefore, to determine the incidence of EIA at stud farms in the state of Minas Gerais, Brazil, a serological survey was conducted to estimate the prevalence and identify potential risk factors for equine infectious anemia virus (EIAV) transmission. This was the second stage of an ongoing study on the epidemiology of the disease, which was first observed in draft horses. A sample of 7,742 equids from 717 stud farms in seven regions within the State was tested between May 2004 and January 2006. Laboratory tests including enzyme-linked immunosorbent assays and agar gel immunodiffusion were conducted for screening and confirmation, respectively. The prevalence of EIA was estimated to be 0.44% (95% confidence interval [CI]=0.00-0.871) at the farm level and 0.07% (95% CI=0.00-0.251) at the animal level. The low prevalence of EIA in stud farms might be explained by the higher zootechnical value of stable-bred animals, which leads to periodical serological control and compliance with the slaughter of test-positive animals in order to keep the farm EIA-free. Moreover, stable-bred horses usually travel more and are subjected to more official controls than are draft horses. The highest prevalence of EIA was observed in regions 1 (North/Northwest of Minas Gerais) and 2 (Vale do Mucuri/Jequitinhonha), with rates of 0.34% and 0.72%, respectively. These results show that the prevalence of EIA at stud farms in Minas Gerais is generally low, with the prevalence being higher in the northern part of the State (regions 1 and 2). A previous serological survey on EIA among draft horses showed a very similar distribution of EIA infection in Minas Gerais. These results suggest a very similar pattern of EIA distribution across the State and irrespective of zootechnical value, but the northern/northwestern regions have a higher prevalence than do the southern regions.