[Naturally-acquired microsporidia (Encephalitozoon cuniculi) infections in hens]

During a short period of time, four approximately ten months old chickens from an egg production (group A) unit developed symptoms of apathy, lameness, mild diarrhoea and loss of weight. The layers were killed and submitted for necropsy. For the first time, microsporidia infection, probably Encephalitozoon cuniculi (E.c.) was diagnosed in chickens. The diagnosis was mainly based on immunohistochemical methods. E.c. was found particularly in the cells of the cutaneous mucous membrane of the crop and in epithelial cells, the cells of the propria mucosae and the smooth muscle cells of the small intestine. E.c. also frequently occurred in the fibres of the skeletal muscle. Intracellularly, E.c. and its development stages were located primarily in the cytoplasm and less frequently in the nucleus of cells. Retrospective investigations on tissue samples from a domestic cock and 9 hens by immunohistochemical methods also revealed occurrence of this microsporidian. The results showed that in chickens E.c. infections can cause multi-symptomatic illness but may also be clinically inapparent.