Compounds that inhibit digestion in blood-ingesting pests are described herein. In one embodiment, the compounds described herein block entry of blood into the midgut and thereby inhibit digestion and nutrient processing. In another embodiment, the compounds described herein prevent pathogens contained in the blood meal from entering the midgut where they could cross the epithelial cell layer and infect the mosquito. The compounds can be administered to a population of blood-ingesting pests, such as mosquitos, directly or indirectly in an effective amount to prevent mosquitoes from transmitting diseases such as malaria, dengue fever, West Nile virus and lymphatic filariasis. Preferably, the compounds are lethal to blood-ingesting pests. The compounds can be combined with one or more excipients to prepare compositions.