helminthes

Helminths, commonly referred to as parasitic worms, are multicellular eukaryotic organisms that live in or on host organisms and derive nutrients at the host's expense. In humans, they are traditionally grouped into three broad categories: nematodes (roundworms), cestodes (tapeworms), and trematodes (flukes). Helminth infections are among the most common tropical and subtropical diseases, but they occur worldwide.

Life cycles are often complex and may involve one or more intermediate hosts. Transmission routes include ingestion of eggs or larvae in contaminated food or water, skin penetration by larvae (as with hookworms), and, for some species, transmission by intermediate vectors such as snails or fish. Adults typically reside in the gastrointestinal tract or tissues, where they may cause mechanical damage, inflammation, and nutrient loss.

Clinical manifestations vary by species and burden but commonly include abdominal pain, diarrhea, weight loss, anemia, hepatosplenic involvement, or obstructive issues. Chronic infections can lead to growth impairment in children and hypersensitivity reactions. Diagnosis relies on detection of parasite eggs or larvae in stool or tissue samples, serology for certain infections, imaging, or endoscopy.

Treatment depends on the species and may involve specific anthelmintic drugs such as albendazole or mebendazole for nematodes, praziquantel for cestodes and trematodes, and ivermectin for certain filarial infections. Preventive measures focus on improved sanitation, safe water, proper cooking of meat and fish, personal hygiene, and control of intermediate hosts where feasible.