The present study was carried out to determine the variations of heamathological and biochemical parameters in different parasitic burden and the correlation between faecal egg counts and fluke number in liver of sheep naturally infected with Dicrocoelium dendriticum. In order to detect elimination of D. dendriticum eggs, faecal samples from 120 sheep of different age groups were collected individually at slaughterhouse in Neyshabur County in Razavi Khorasan Province during December 2013 - October 2014. Moreover, heamatological and blood biochemical values in 120 sheep naturally infected with D. dendriticum were compared with equivalent values in 120 parasite-free sheep from organically farmed flock. Investigated animals were kept in outdoor system, on pastures covered with swamps, which remain flooded after rainy season. Total number of flukes in liver obtained in infected sheep at necropsy varied between 10 and 18500. A positive relationship can be seen via the correlation coefficient (r= 0.94, P < 0.001) between the number of eggs excreted by each sheep and that of total fluke counts recovered in the liver. Significantly lower RBC, PCV, neutrophil and albumin were observed in parasitized sheep, when compared to the healthy animals. However, WBC, lymphocyte and AST values were significantly higher in parasitized sheep. No significant correlation was detected between the heamatological and biochemical parameters and the number of D. dendriticum in the liver. It was concluded that infection with more than 400 D. dendriticum in the liver could be diagnosed by EPG. However, there was no relationship between the parasite burden and heamatological and biochemical parameters.

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