[Enzootic dermonecrosis in chickens].

An enzootic of necrotic dermatosis in hen layers was described. The changes consisted in that they had constant localization and demarkated sites on the skin between the back and the neck. The disease was observed on a farm for 5000 layers in the course of two consecutive years. All birds contracted the disease and in the first year they recovered the 10 months; in second year they recovered for three months. Each bird showed symptoms for 3 weeks. The skin lesions resulted in cicatrization. The etiologic agent (a Pasteurella-like organism) was isolated from the necrotic foci. It proved pathogenic for albino mice and manifested biochemical activity and morphology characteristic of Pasteurella multocida. The disease was successfully reproduced with a broth culture applied on a scarified skin of test birds. Histopathologically, the spontaneous lesions proved undistinguishable from the experimental ones and represented coagulation necrosis of the epidermis, derm, and subcutis. It is supposed that the constant localization was due to the porte d'entrer of the infection, associated with the bad habit of picage on the neck as demonstrated on a large scale by the birds of the infected flock. This is characteristic of some lines of the White Leghorn breed.