Correlation of Estimated and Actual Northern Fowl Mite Populations with the Evolution of Specific Antibody to a Low Molecular Weight Polypeptide in the Sera of Infested Hens

In order to demonstrate the population dynamics of the northern fowl mite (NFM), Ornithonyssus sylviarum (Canestrini and Fanzago), and to characterize the chicken's immune response to the mites, White Leghorn hens were infested with mites. Visual estimates revealed populations peaked on Wk 5, 4, and 3 after being infested with 10, 50, or about 2,000 mites, respectively. Individual feathers pulled from the vent area of hens 4 wk (28 days) after the hens were infested with either 10 or 50 mites had means of 7,513 and 7,009 mites, respectively. Estimated mean total populations of NFM on these same hens were 182,000 and 258,000, respectively. In two replications, actual counts of viable NFM following infestation with 50 mites increased ca. 10-fold by the 2nd wk after infestations were established in the feathers and then another two-fold during the 3rd wk. Populations in the 4th wk were about one-third of levels observed during the 3rd wk and continued to decline rapidly. Western blot analyses demonstrated the appearance of a mite-specific antibody in sera of White Leghorn hens that was approximately proportional in time of appearance and intensity to estimated NFM populations. Detection of mite-specific antibodies in the hens' sera continued through 12 wk of the study even though mite populations declined after 3 to 6 wk. The rapid increase and then decline of NFM following infestation in previously uninfested chickens and the fact that the immune response persisted strongly suggests that the population decline was due to an immune response. Therefore control of the mite population by a vaccine may be possible.