Aspectos epidemiológicos de Fasciola hepatica nos municípios de Pedro Leopoldo e São José da Lapa - Minas Gerais, e avaliação da infecção experimental em ovinos da raça Santa Inês

Abstract

Fasciola hepatica (Linnaeus, 1758) is a digenetic trematode that parasitizes the hepatic parenchyma and bile ducts of ruminants and other mammals, including humans. It is the etiologic agent of fasciolosis, a disease of great importance in veterinary medicine, due to economic losses in livestock. Fasciolosis is expanding in Brazil with the biggest enzootic area is situated in the south, followed by the southeast and center-west regions. In Minas Gerais, registers are noted in an isolated manner and new cases in regions once considered unaffected have been reported. This project evaluated the occurrence of the fluke in cattle and buffalo herds in the municipalities of Pedro Leopoldo and São José da Lapa, located in the metropolitan region of Belo Horizonte. Surveys were conducted concerning the condemnation of livers in slaughterhouse, the examination of faecal samples in herds from rural properties and natural infection analysis by the fluke in snails of the genus Lymnaea. Condemned livers were observed due to parasitism by F. hepatica in cattle and buffaloes from those municipalities. During epidemiological inquiry, a total of 65 rural properties were visited, whence 29 presented at least one ruminant naturally infected. 0.3% of snails collected were infected by F. hepatica. For better understanding of the aspects of this host-parasite interaction, sheep from Santa Inês breed were experimentally infected and followed during the acute and chronic phases of the infection, with the evaluation of parasitological, hematological and immunological parameters. The sheep show themselves susceptible to infection, eliminating eggs in the faecal sample around 60 dpi. These animals presented anemia and eosinophilia during experimental period. Cytokines TGF-1 and nitric oxide (NO), typical of an innate immune response, were detected in PBMC culture supernatants during the acute and chronic phases of the infection. Participation of IgG was also evaluated, and it was observed that this antibody is produced in high taxes at the beginning of infection, and its values decline over time, demonstrating that this response does not provide protection to the host against the fluke. Based on the obtained data, it was concluded that F. hepatica is in expansion in Minas Gerais. Cattle, buffaloes and snails Lymnaea are naturally found infected in the municipalities of Pedro Leopoldo and São José da Lapa, proving the occurrence of the fluke life cycle in the region, which may be a source of contamination for nearby areas. Sheep from Santa Inês breed are susceptible to infection, with the occurrence of significant hematological and immunological alterations throughout the infection, suggesting a mixed Th1-Th2-type response in the chronic phase of fasciolosis.