RESUMO
Ovine protozoan myeloencephalitis is a disease of sheep associated with the apicomplexan protozoan Sarcocystis tenella. This paper describes the clinical, pathological and epidemiological findings in three affected flocks from a well-defined geographical area. Clinical signs were restricted to sheep under one year old in their first winter and were first observed at least 42 days after they had been moved off the hill grazing areas to low ground pasture, or after they were given conserved forage. The findings are discussed in relation to the timescale of the life cycle of S. tenella and it is suggested that clinical disease was precipitated by the change from a low level of exposure to infection on the hill to a high level of exposure through contaminated pasture or forage. Possible preventive strategies are discussed.
Assuntos
Surtos de Doenças/veterinária , Encefalomielite/veterinária , Sarcocystis/patogenicidade , Sarcocistose/veterinária , Doenças dos Ovinos/parasitologia , Ração Animal , Animais , Encefalomielite/parasitologia , Encefalomielite/patologia , Feminino , Estágios do Ciclo de Vida , Poaceae , Sarcocistose/epidemiologia , Sarcocistose/patologia , Estações do Ano , Ovinos , Doenças dos Ovinos/epidemiologia , Doenças dos Ovinos/patologiaRESUMO
Eight isolates of Bovine respiratory syncytial virus (BRSV) were made from calves with severe respiratory disease on seven farms in one region of Britain. Genetic analysis of the viruses showed that seven, which were isolated between 1997 and 1999 were almost identical and were distinguishable from an earlier 1991 isolate. When compared with the available sequences of BRSVs from other countries, the recent British isolates were more closely related to US isolates than to earlier British and current mainland European isolates.