Epidemiological Survey of Cestode-larva Disease in Greek Sheep Flocks

The epidemiological status of hydatidosis, cysticercosis, and gid in sheep and the production practices of sheep farmers that increase the risk of exposure of sheep to infecting agents of these diseases were investigated in Thessaly, central Greece during 2002-2006. A total of 700 hoggets (sheep up to the age of 1 year) and 1500 adult sheep were examined randomly at an abattoir survey and the prevalences of hydatidosis and cysticercosis were found 39.32% and 29.41%, respectively. Hoggets had significantly lower prevalences of hydatidosis and cysticercosis compared to adult sheep (p<0.001). The distribution of parasitic cysts showed an overdispersion pattern mostly in the hogget population. The proportion of fertile hydatid cysts was significantly higher in hoggets compared to adult sheep (p<0.001). A cohort of 74 sheep flocks was observed during the same period in a prospective survey to assess the incidence of gid. A total of 57 sheep belonging to 15 flocks (20.27% of investigated flocks) developed clinical signs of gid at an annual rate of 11.40+/-4.77 (95% C.I.). In the infected flocks there were 3.80+/-0.92 (95% C.I.) gid cases per flock. The mean age of onset of clinical signs for all sheep was 11.86+/-1.33 months (95% C.I.) (range 5-22 months) while for hoggets was 8.48+/-0.73 (95% C.I.) (range 5-12 months) and for adult sheep 17.23+/-1.42 (95% C.I.) (range 13-22 months). A significant difference was observed in the prevalence of unilateral blindness between hoggets (31.42%) and adult sheep (4.54%) (p<0.05). The most common production practices identified in a questionnaire survey of sheep farmers that may increase the risk of exposure of sheep to hydatidosis, cysticercosis, and gid were the improper disposal of dead animals, the access of farm dogs to offal of slaughtered sheep, the carelessness of farmers to treat farm dogs with anthelmintics, and the grazing of flocks in fields where stray dogs have free access.