Effect of ivermectin on the ovarian development of Aedes aegypti (Diptera: Culicidae).

The effect of ivermectin (0.1 microgram/ml) on blood digestion, ovarian development, and ovipositional attributes of Aedes aegypti was studied using standard morphological and histological techniques. Uncoordinated movements and paralysis were observed in most ivermectin-treated females within 1 h after ingestion of blood containing the chemical. Eight days after the blood meal, 23.5% of the treated females had died, whereas no mortality occurred in controls. Formation of the peritrophic membrane and digestion of the blood meal were delayed in the surviving treated mosquitoes. The most striking effect of ivermectin on Ae. aegypti at this dosage was on ovarian development. Changes observed among ivermectin-treated mosquitoes included: blood digestion without development of ovarian follicles; degeneration of primary follicles and formation of ovarian dilatations within 24 h after ingestion of the chemical; significant reduction in the rate of vitellogenesis and follicle development; decreased egg production; reduced egg hatching; abnormal egg size and shape; and increased percentages of unhatched embryonated and sterile eggs. Although the precise action of ivermectin on Ae. aegypti is unknown, our studies indicate that the chemical directly or indirectly affects at least three major organ systems (nervous, digestive, and reproductive).