The generally warm, moist environmental conditions in the Northwestern Iran are ideal for survival and growth of the egg and larval stages of Haemonchus contortus and other gastrointestinal nematodes (GIN) of sheep and goats.A total of 2,421 animals were slaughtered and examined from July 2010 to July 2011 in Urmia abattoir. In case of sheep, 225 out of 2,421 were positive and prevalence of H. contortus infestation was 9.3 %. Sex wise prevalence of H. contortus in sheep was 33.08 % (76/229) in male and 66.22 % (149/225) in female. The females indicated significantly (P < 0.05) higher prevalence (66.22 %) as compared to males (33.08 %). The highest prevalence was recorded in the spring (April) and the lowest was in summer (July), respectively. On microscopic examination, infiltration of mononuclear cells and eosinophils in gastric glands, periglandular hyperemia and hemorrhage, mucous gland hyperplasia, connective tissue proliferation and necrosis was observed. Also, in mixed abomasal infection with Haemonchus and Ostertagia species, mucosal hyperplasia and increased mucous glands and sometimes cystic glands were seen. Statistical analysis using SPSS software, and Chi-square test, demonstrated a non-significant difference between ages and abomasal PH values of infected and healthy sheep (P < 0.05). But the difference between sexes, seasons and abomasal lesions was significant (P > 0.05).
Keywords: Abomasal; Haemonchus; Sheep; Statistical; Urmia.