helminth

Helminth is a term for multicellular parasitic worms that infect humans and other animals. In medical and veterinary contexts, it usually refers to three groups: nematodes (roundworms), cestodes (tapeworms), and trematodes (flukes). Helminths are obligate parasites; adult worms reside in hosts and produce eggs or larvae that pass into the environment, enabling transmission.

These parasites have diverse life cycles. Some species have a direct life cycle, requiring only a single host, while others are indirect, involving intermediate hosts or vectors. Transmission routes include ingestion of eggs or larvae in contaminated food or water, skin penetration by larvae, or, for some species, through undercooked meat or vectors.

Clinical impact depends on the parasite and site. Intestinal nematodes commonly cause abdominal pain, diarrhea, malnutrition, and anemia; tissue-dwelling flukes and schistosomes can cause organ inflammation and fibrosis. Diagnosis relies on detecting parasite eggs or DNA in stool, urine, or blood, along with serology or imaging in certain cases.

Treatment relies on anthelmintic drugs. Albendazole and mebendazole are widely used for many nematodes; praziquantel is effective against most cestodes and trematodes; ivermectin targets several filarial infections and other nematodes. Choice depends on species, geographic area, and patient factors.

Prevention focuses on sanitation, clean water, proper food handling, cooking of meat, and measures to reduce exposure in endemic areas. Mass drug administration programs are used in some regions to control parasite burden. Helminth infections are among recognized neglected tropical diseases, influencing public health strategies worldwide.