Helminthiasis, also known as worm infection, is any macroparasitic disease of humans and other animals in which a part of the body is infected with parasitic worms. Over 250 species of helminths may parasite on humans either asymptomatically or causing a disease. Helminthiasis is the most common infection worldwide affecting about 1/3 of the entire population, especially in the developing countries with a lower level of personal hygiene and polluted environment (unhygienic conditions in living quarters or working premises, pollution of water bodies and soil with feces, etc.). In the human body the helminths can affect not only the intestine, but also other organs, for example, the liver, kidneys, blood vessels, pancreas, lungs, and brain.
Helminthiasis seldom leads to fatality, but it is the main cause of deteriorating health and quality of life of the patients.
Helminths include members of the following taxonomic units: tapeworms, or cesto-des, flukes, or trematodes (both these groups belong to flatworms) and roundworms, or nematodes.
Helminths can be classified into 3 groups according to the mode of transmission and their biological features:
• biohelminths;
• geohelminths (soil-transmitted helminths);
• contact helminths. Representatives of biohelminths include
pork tapeworm, beef tapeworm, echinococcus and other species of cestodes, trematodes and certain species of nematodes. Their life cycle involves one-two-three successive hosts; intermediate hosts are usually fish, mollusks, crustaceans, and insects. Sometimes, an intermediate host may be a human - the carrier of larval forms of unilocular and multilocular echinococ-cus or cysticercus, pork tapeworm larvae.
Humans can become infected with biohel-minths by eating contaminated meat that was not subjected to proper thermal processing: beef infected with beef tapeworm measles, pork infected with pork tapeworm measles, soft-salted and uncooked fish with liver fluke or broad tapeworm larvae. Larvae of certain helminths may swim in the water or attach to the seaweeds; in this case a person may contract an infection while drinking fresh water infected with larvae, washing vegetables, fruit and dishes with such water, eating infected water plants.