The working equid population in Corumbá, Southern Pantanal, is very large and has a crucial role in the main economic activity of the State of Mato Grosso do Sul, the beef cattle industry. The aim of the present study was to estimate the prevalence of equine infectious anaemia (EIA) in working equids of ranches in the municipality of Corumbá, by the official agar gel immunodiffusion (AGID) test, and evaluate the adoption of the Programme for the Prevention and Control of Equine Infectious Anaemia proposed by Embrapa Pantanal and official entities in the 1990s. From September to November 2009, forty ranches distributed through the area of the municipality were visited, and serum samples were obtained from 721 equines and 232 mules. According to previous publications and the present data, it was concluded that the prevalence of EIA in this population has increased from 18.17% to 38.60%, which represents at this time approximately 13,000 infected animals. There was no significant difference between the apparent prevalence of equines and mules. It was also verified that the control programme was not known by the greater part of the interviewed ranch owners, managers and foremen and, in their perception, EIA is not a primary threat to address. Among the studied variables, the serologic testing practice significantly reduced the risk for the presence of EIA seropositivity, as well as the separation of riding equipment and segregation of seropositives.