Abstract: An epidemiological study was done from 2002 to 2003, in order to determination of prevalence of D.gallinae infestation in egg laying flocks in Mashhad area. Twenty-four flocks were randomly selected and has been sampled one month interval for three times. First, every houses of farm were carefully inspected about presence of absence mite infestation and then dust samples were collected in everywhere of houses, simultaneously; ten blood samples were collected for measurement of packed cell volume (PCV) in hens in each house .In this study, D.gallinae infestation was detected in eleven farms (43.45%). The PCV of hens in infested farms were below the normal range (p<0.05). This infestation was caused to decrease egg production with a rate of 17% to 25%. In this study , some variable related to hygiene management in infested and non- infested farms were compared and analyzed ,the results of this study were shown that the hygiene management was poor in infested farms (p<0.05). In based on the high prevalence of Dermanyssus infestation in egg laying farms in Mashhad area, it needs to do a control program for this mite in the infested farms.

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