Filarial parasites Brugia, Wuchereria, Loa Loa and Onchocerca cause over 20 million infections worldwide and pose a significant social and economic burden in endemic areas. The invention provides compositions and methods to treat parasitic infections in animals and plants, and to kill and inhibit the replication of parasites in infected hosts. The methods can include administering to a host in need of treatment an effective antiparasitic amount of a composition comprising biodegradable polyanhydride microparticles or nanoparticles that encapsulate antiparasitic agents, optionally in combination with antibacterial agents. Through co-encapsulation of antiparasitic and antibacterial agents into the particles, the invention provides the ability to effectively kill parasitic helminthes, worms, and flukes, with up to a 40-fold reduction in the amount of drug used. The results described herein demonstrate the effectiveness of the drug carriers to reduce both the course of treatment and the amount of drug needed to treat parasitic infections.
