Dermatophilus congolensis infection in goats in Tanzania

When goats in Eastern Tanzania were screened for skin diseases, Dermatophil us congolensis was isolated from the skin lesions in 8 of 484 animals exami ned. In one severely affected case, the disease was also characterized by h istological studies (Gram stain, Giemsa stain and routine HE studies) and e lectron microscopy. The histological picture was characterized by hyperkera tosis, parakeratosis, acanthosis, folliculitis and an inflammatory cellular reaction involving the epidermis. Gram stain and Giemsa stain revealed lon gitudinal and transverse branching filaments in the deeper layers of the ep idermis. Ultrastructural studies demonstrated D. congolensis in various mor phological forms, ranging from filamentous to tuber-shaped structures, mixe d with numerous coccoid bodies of variable size. In some instances, the org anisms were geometrically arranged in parallel rows of beading and were pre sent in and among the degenerated epithelial cells. Several host cells show ed degenerative changes. Ticks present on the goats were Amblyomma variegat um, Rhipicephalus evertsi, Rhipicephalus pravus and Boophilus sp. The clini cal signs, pathological lesions, diagnosis, epidemiology and pathogenesis o f the disease are discussed.