34 



One of the longstanding economic reasons for keeping flocks free 

 of northern fowl mites has been that mites cause a drop in egg produc- 

 tion (Cameron, 1938; Metcalf et al . , 1962; Anonymous, 1967; Koehler, 

 1977; Rock, 1978; Smith, 1978). Combs et al . ( 1 976) -demonstrated 

 that chemical removal of mites improved egg production. Other work 

 done in the last 10 years also conflicts with studies attributing 

 decreased egg production to northern fowl mites. Loomis et al. (1970) 

 could find no significant difference in egg production due to mite 

 populations. Bramhall (1972) discounts northern fowl mites as a 

 reason for reduced egg production and suggests that poultrymen control 

 mites only to prevent discomfort to workers. Eleazer (1978) found that 

 uncontrolled northern fowl mite infestations did not cause reduced egg 

 production and DeVaney (1979) reported that during two separate 1-year 

 trials a significant reduction in egg production was produced by mites 

 for only 1 month in one trial, and 2 months in the other. 

 Medical Importance of Northern Fowl Mites 

 Al lergic reactions 



Gamasoidos i s , a poultry handlers' dermatitis caused by fowl mites, 

 was reported in 1824 (Toomey, 1921). It has since been well established 

 that northern fowl mites will attack man and produce transitory rashes 

 on the skin (Riley and Johannsen, 1915; Van Der Hoeden , 1964; Frazier, 

 1969; James and Harwocd, 1969; Georgi, 1974; Ebelinq, 1975). 



Riley and Johannsen (1915/ called the mite-produced rash a pruritis 

 and not a dermatitis since man does not present favorable conditions for 

 mite viability. Both terms, pruritis and dermatitis, have been used by 

 recent authors to describe the condition (Cahn and Shechter, 1958; 



