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any one disease of man, animals, and plants caused by nematodes. In humans the parasites are localized in most tissues and organs, including the gastrointestinal tract, muscles, respiratory organs, liver, and kidneys. The causative agents of some nematodiases develop in the external environment in soil, water, and everyday objects. Some nematodiases have causative agents whose development is associated with a succession of hosts. Humans become infected by swallowing particles of soil, water, or food products contaminated by mature nematode (invasive) eggs or larvae. The preservation and development of nematode eggs and larvae in the external environment require certain temperature conditions and sufficient moisture and oxygen. In the USSR the following diseases caused by nematodes have been recorded in humans: ascariasis, enterobiasis, trichochuriasis, and trichinosis.
In animals. Nematodiases are known to occur in all species of vertebrates. The causative agents are localized in almost all body organs and tissues (most parasitize the digestive tract). The occurrence of the diseases is governed by climatic conditions, the presence and number of intermediate hosts, maintenance conditions of the animals, the quality of treatment and prophylactic measures, and a number of other factors. The greatest economic losses to animal husbandry are caused by ascariasis, ascaridiosis, amidostomosis, bunostomiasis, dictyocaulosis, alfortiosis, and trichinosis. (See also.)