n order to identify prevalence of clinical coccidiosis in laying hens and to find out correlation of clinical sign with OPG in the litter in Mashhad area, Khorasan province, this study has been done . Among 172 layer farms in Mashhad area, 17 farms were randomly selected . Samples were collected weekly from litter of each farm between 3rd and 13th week. An estimation of the oocyst per gram (OPG) was done with modified Claytone lane and modified Mac-Master methods. Among ten infected farms , clinical coccidiosis were iagnosed in six farm(35%) . Five farms had deep litter system and one farm with cage system. Most of the clinical coccidiosis were observed in 7-9 weeks old. A significant correlation was observed between clinical coccidiosis and litter OPG. In this study, E. maxima (53%), E. acervulina (47%) , E. necatrix (41%) and E. tenella (35%) were identified . E. necatrix was the most importance agent to cause clinical coccidiosis. Based on the results , clinical coccidiosis is one of the prevalent disease in the layer farms in Mashhad area and controlling programs against occidiosis must be in the pullet breeding period.

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