Most Worms Do Not Multiply in Human Host

Helminths have complex life cycles, but in many of the species of human parasites (with a few important exceptions), the adult worms do not actually multiply in the human host. Thus, in most of these helminth infections, each individual parasite may be considered to be the result of a separately acquired infective stage.

However, a few of the helminths that infect humans can either complete their entire life cycle in the same host (such as in strongyloidiasis) or infect humans only during the larval phase (e.g. larva migrans, hydatidosis, cysticercosis). They are much less common, but can cause much more serious disease. Thus, the principal value of chemotherapeutic agents in these infections is in the treatment of the individual rather than in controlling transmission.

Many of the anthelmintics available for human use are effective against several helminth species, and although there are over 20 different species of helminths that cause disease of global significance in humans (see table 1), almost all of these infections can be treated or controlled with one of 5 anthelmintics: the benzimidazoles albendazole and mebendazole, diethylcarbamazine, ivermectin, and praziquantel.