Precipitating Antibody Concentrations and Visual Estimates Correlated to Absolute Northern Fowl Mite (acari: Macronyssidae) Densities from White Rock Hens

Fifty-four White Rock hens were infested with 2,000 northern fowl mites/ bird and six hens were sampled at nine time periods during the 28,week study. Hens supported an average of 15,028 mites when mites were collected from infested bird carcasses digested with a modification of the Cook's technique. Mite-specific Ilrccipitating antibodies were quantified from hen serum samples with rocket electrophoresis. Seventy-foUl' percent of the serum samples gave quontifiabJe results. A reduction in antibody concentrations was observed with increased mite population densities suggesting that immunosuppressive or tolerance mechanisms may playa role in the host's humoral immune response to a mite inrestation. A visual mite density rating index was more accurate in assessing mite population densit.ies than quantitative antibody measurements. Key "'lords: Northern rowl mite, host immunit)" rocket electrophoresis, population density. J. Agric. Entomol. G(3l: 153-157 (July 1989) The northern fowl mite, OrnithollYsSU.S sylviarum (Canestl'ini and F'anzago), is one of the most serious arthropod pests affecting poultry production in the United States (DeVaney 1978). As obligate, hematophagous parasites, mites complete theil' entire five stage (egg, larva, protonymph, deutonymph and adult) life cycle on an avian host. Only pl'otonymphs and adults are known to feed (Sikes and Chamberlain 1954), Large populations (> 50,000 mites! bird) have the potential of consuming 6% of the total blood volume/ day of a 1.5 kg hen (DeLoach and DeVaney 1981). Matthysse ot. al. (1974) and DeVaney and Ziprin (l980b) detected the presence of mite-specific, precipitating antibodies in the sera of infested \-Vhite Leghorn chickens with an agar-gel diffusion technique and showed a positive correlation between percentage of positive agar-gel tests and mite infestation severity. Quantitative measurements of mite-specific, precipitating antibody concentrations and comparisons with absolute mite numbers have not been made to date. Precipitating antibody concentrations (IAbJ) and antigen volumes have been correlated with rocket electrophoresis (RE) (Laurell 1966), and IAbl can be quantified with this technique. Electrophoretic migration of antigen into antibodyI Current address: Department of Entomology, University of Kentucky, Lexington, KY 40546­ 009J. 1 Current address: Department or Entomology. fvIississippi State, 1\'15 39762. .3 Department of Molecular and Cell Biology, The Pennsylvania State University.