Parasitic Diseases

diseases of man and animals caused by infection with unicellular protozoans, worms, ticks, and some arthropods. Depending on the type of causal agent, parasitic diseases are divided into the protozoiases (causal agents, protozoans), helminthiases (worms), acariases (ticks), and entomiases (insects). The causal agents may live on the body surface (ectoparasites) or within the body of man or animals (endoparasites). The most widespread protozoan diseases are malaria, toxoplasmosis, trypanosomiasis, amebiasis, lambliasis, coccidiosis, trichomoniasis, and leishmaniasis. Of the helminthiases the most common are ascariasis, trichinosis, enterobiasis, ancylostomiasis, filariasis, dracunculiasis, taeniasis, hymenolepiasis, diphyllobothriasis, opisthorchosis, schistosomiasis, and echinococcosis; altogether more than 200 diseases are caused by worms. Scabies, myiasis, and pediculosis are well known acariases and entomiases.

The sources of parasitic diseases are organisms, called hosts, which carry the causal agent, either in a diseased state or as parasite vectors. The hosts of parasitic diseases may be man (anthroponoses) or animals (zoonoses), and the diseases may be transmitted by contact, for example, with a sick person or a horse, as in scabies, by swallowing the causal agent or its eggs, as in ascariasis and amebiasis, or by penetration of the larvae through injured skin, as in ancylostomiasis and strongylosis. The causal agents of certain parasitic diseases, such as leishmaniasis and malaria, are transmitted by arthropod vectors.