Treatment for Infections Caused by Nematodes

Infection by helminths (worms) may be limited solely to the intestinal lumen or may involve a complex process with migration of the adult or immature worm through the body before localization in a particular tissue. Complicating our understanding of the host– parasite relationship and the role of chemotherapy in helminth-induced infections is the complex life cycle of many of these organisms.Whereas some helminths have a simple cycle of egg deposition and development of the egg to produce a mature worm, others must progress through one or more hosts and one or more morphological stages, each metabolically distinct from the other, before emerging as an adult. Furthermore, an infective form may be either an adult worm or an immature worm. Treatment may be further complicated by infection with more than one genus of helminth. Pathogenic helminths can be divided into the following major groups: cestodes (flatworms), nematodes (roundworms), trematodes (flukes) and less frequently, Acanthocephala (thorny-headed worms). The complex life cycle and host–parasite relationship means that treatment is sometimes difficult and may have to be protracted. Most available anthelmintic drugs exert their antiparasitic effects by interference with (1) energy metabolism, (2) neuromuscular coordination, (3) microtubular function, and (4) cellular permeability. The mode of action of most drugs used in the treatment of helminthic infections is summarized in Table 54.1. Some of the drugs used in the treatment of diseases caused by helminths also are used in the treatment of specific protozoal diseases.