The effects of ivermectin on the hydatid cyst of Echinococcus granulosus after direct injection at laparotomy.

The effect of ivermectin on the hydatid cysts of Echinococcus granulosus was studied in vivo. Jirds were infected with secondary hydatid cysts of E. granulosus by intraperitoneal passage. One to one and a half years postinfection a laparotomy was performed on each of 20 jirds and the hydatid cysts located. Ivermectin or the vehicle (1% dimethyl sulfoxide in sterile physiological saline) was injected into a single hydatid cyst in each animal (10 with ivermectin; 10 with vehicle as control). The jirds were killed 44-58 days postsurgery and necropsied. The integrity of each injected cyst was assessed and tissue samples were taken for microscopic examination. Treated cysts were discolored, collapsed, and had no viable protoscolices. The germinal layer of treated hydatid cysts was necrotic; the laminated layer was intact. The effects were restricted to the ivermectin-treated cysts. Treated cysts were not infective to naive jirds by intraperitoneal passage.