A Pathological Study on Taenia hydatigena Larval Lesions and its Infection Rate in Sheep

Cysticercus tenuicollis is the larval stage of Taenia hydatigena، the presence of which has been reported in wild and domestic ruminants throughout the world. It is a common parasite of sheep in Iran. This study was undertaken to determine Cysticercus tenuicollis infection rate، to rank the severity of its hepatic lesions and to describe the pathological characteristics of the lesions in sheep. Out of 340 examined sheep (259 in Najaf Abad and 81 in Joneghan abattoir)، 65 (25. 48%) and 30 (37%) were infected with Cysticercus tenuicollis، respectively. This cyst was observed in different anatomic locations including liver، mesentery، omentum، peritoneum and diaphragm. There was no Cysticercus tenuicollis in the heart and lung of slaughtered sheep. The liver of the infected sheep showed multiple red to brown or greyish-white tortuous tracts. The histopathological examination of newly formed hepatic lesions revealed migratory tracts filled with red blood cells، fibrin and tissue debris. The sections of Taenia hydatigena larvae، hepatocellular degeneration، necrosis، and infiltration of inflammatory cells were observed in the migratory canals too. Caseous necrosis and calcification were seen in the central part of old migratory tracts. A large number of macrophages or epithelioid cells and giant cells were seen around the necrotic area. These structures were surrounded with collagenous connective tissue infiltrated by lymphocytes and plasma cells. To rank hepatic lesions، the number of migratory tracts، in hepatic surfaces were counted and assigned to one of the following categories including mild (1-4 migratory tracts)، moderate (5-10) and severe (>10) and the results were 76. 19%، 19. 05% and 4. 76%، respectively. The results of this study show that the migration of Taenia hydatigena larvae can cause economic losses and the disease control programs are recommended and emphasized.