Dermatophilus congolensis infection in goats in Tanzania.

When goats in Eastern Tanzania were screened for skin diseases, Dermatophilus congolensis was isolated from the skin lesions in 8 of 484 animals examined. In one severely affected case, the disease was also characterized by histological studies (Gram stain, Giemsa stain and routine HE studies) and electron microscopy. The histological picture was characterized by hyperkeratosis, parakeratosis, acanthosis, folliculitis and an inflammatory cellular reaction involving the epidermis. Gram stain and Giemsa stain revealed longitudinal and transverse branching filaments in the deeper layers of the epidermis. Ultrastructural studies demonstrated D. congolensis in various morphological forms, ranging from filamentous to tuber-shaped structures, mixed with numerous coccoid bodies of variable size. In some instances, the organisms were geometrically arranged in parallel rows of beading and were present in and among the degenerated epithelial cells. Several host cells showed degenerative changes. Ticks present on the goats were Amblyomma variegatum, Rhipicephalus evertsi, Rhipicephalus pravus and Boophilus sp. The clinical signs, pathological lesions, diagnosis, epidemiology and pathogenesis of the disease are discussed.