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Parasitic worms cannot reproduce entirely within their host's body; they have a life cycle that includes some stages that need to take place outside of the host. [3] Helminths are able to survive in their mammalian hosts for many years due to their ability to manipulate the host's immune response by secreting immunomodulatory products. [4]
Major groups of parasites include protozoans (organisms having only one cell) and parasitic worms (helminths). Of these, protozoans, including cryptosporidium, microsporidia, and isospora, are most common in HIV-infected persons. Each of these parasites can infect the digestive tract, and sometimes two or more can cause infection at the same time.
The soil-transmitted helminths (A. lumbricoides, T. trichiura, N. americanus, A. duodenale), schistosomes, and filarial worms collectively infect more than a quarter of the human population worldwide at any one time, far surpassing HIV and malaria together. [35] [37] Schistosomiasis is the second most prevalent parasitic disease of humans after ...
The pinworm (species Enterobius vermicularis), also known as threadworm (in the United Kingdom, Australia and New Zealand) or seatworm, is a parasitic worm.It is a nematode (roundworm) and a common intestinal parasite or helminth, especially in humans. [7]
Obligate parasites may not necessarily spend all of their time behaving as parasites. When a parasite is permanent, a number of generations occur in or on the host of an infested individual. Head lice are an example of this. Temporary parasites are organisms whose parasitic mode of life is limited to a few or even one stage of development. [2]
Species of the other subclass, Cestodaria, are mainly fish infecting parasites. All cestodes are parasitic; many have complex life histories, including a stage in a definitive (main) host in which the adults grow and reproduce, often for years, and one or two intermediate stages in which the larvae develop in other hosts.
Hence, "helminthology" is the study of parasitic worms. When a human or an animal, such as a dog or horse, is said to "have worms", it means that it is infested with parasitic worms, typically roundworms or tapeworms. Deworming is a method to kill off the worms that have infected a human or animal by giving anthelmintic drugs.
The helminth Spinochordodes parasitising a bush-cricket (Meconema sp.) A plate from Félix Dujardin's 1845 Histoire naturelle des helminthes ou vers intestinaux. Helminthology is the study of parasitic worms (helminths). The field studies the taxonomy of helminths and their effects on their hosts.