Acquired immune response of white leghorn hens to populations of northern fowl mite, Ornithonyssus sylviarum (Canestrini and Fanzago).

Three levels (high, low and control) of northern fowl mite, Ornithonyssus sylviarum (Canestrini and Fanzago), were maintained on White Leghorn hens for 24 weeks. The hens were then treated with carbaryl to eradicate the mites, were induced to molt, and were reinfested with mites 9 weeks later. Subsequent levels of mites on the three groups showed that the degree of acquired immunity was related to the initial level of mite infestation.