This case report describes Dermanyssus gallinae infestation as a cause of foot self-mutilation in a laying hen (Gallus gallus) flock. The wounds were observed on one or both feet on the dorsal part of the metatarsus and third digit. Some birds have severe lesions - the tendon and muscle were damaged, and the bone of the digit was visible. The high number of red mites on the dead birds and in the poultry house was noted. The warm summer and high temperatures (30^oC) were optimal for red mite development, leading to their high numbers in the environment. The observations suggest that during the examination of foot injuries in birds, self-mutilation caused by red mite invasion should be considered as a possible cause, in addition to pododermatitis and scabies.

Key words: Dermanyssus gallinae, Feet self-mutilation, Hen, Red mite