Histopathological changes of the skin in hens infested with Dermanyssus gallinae.

Studies were carried out on dead hens from a commercial farm of layer hens. Sections of skin from the region of the breast and under the wings with changes following mite bites were taken for histopathological examinations. In the histopathological preparations hyperkeratosis of epidermis and pachydermatosis were ascertained. Numerous lymphocytic cells focally infiltrated the connective tissue and were present under the epidermis. Subcutaneous connective tissue was oedematous. Furthermore, excessive desquamation of the corneal layer of the epidermis and small epidermoidal cysts in dermis occurred, containing callous cells and amorphous protein substances.