An epidemiological study (2009-2010) included cattle and horses affected with pythiosis from farms in Pantanal, Mato Grosso, Brazil. The disease occurred predominantly from November to March annually, period of the local rainy season. The mean annual incidence of pythiosis was 0.22% and 12.5% in cattle and horses, respectively. In cattle, the case distribution occurred during the peak of the floods and was restricted to 6 to 18 months of age heifers. Mild perilesional edema and lameness evolved to spontaneous resolution within until 90 days. In horses, pythiosis affected animals of both sexes with 3 to 8 years of age. Reinfection afflicted one horse. The lesions evolved to extensive granulation tissue and ‘kunkers' in horses that experienced marked cachexy. Death occurred three to seven months after the beginning of symptoms. The mean mortality rate was 5.88% and the case fatality rate was 45.45%. Diagnosis was confirmed by ELISA test, PCR, histopathology (HE and Grocott) and isolation of Pythium insidiosum. In the endemic area studied, the disease in cattle did not represent an economic impact; on the other hand, the majority of cases in horses progressed unsatisfactorily. The incidence of pythiosis in horses was 57.23 times the incidence recorded in cattle, with statistical significance. While environmental flooded conditions were the same, such difference might be associated with species susceptibility, behavior and management.
Oomycetes; pythiosis; horses; cattle; epidemiology; Pythium insidiosum
