Sequential pathological changes in natural and experimental dermatophilosis in Bunaji cattle.

Differences in histopathological changes between experimentally and naturally induced dermatophilosis were slight; natural infections persisted longer as they tended to be complicated by other concurrent dermatoses. Sequential pathological changes in bovine dermatophilosis included congestion, dermal oedema and neutrophilic infiltration of dermal papilae and epidermis by the third day; degenerative changes of cells in the upper portion of the stratum spinosum and invasion of the keratinised layer and hair follicles by the filamentous forms of Dermatophilus congolensis by the fourth day; regenerative processes involving the basal cells and selective cellular destruction in the spinous layer and further hair follicle invasion by D congolensis by the ninth day; and proliferative changes characterised by parakeratosis, hyperkeratosis, acanthosis and dermal sclerosis by the 15th day. It is postulated that cattle with hair follicles parasitised by D congolensis are carriers and are responsible for perpetuation of bovine dermatophilosis from one season to the next.