From Big Medical Encyclopedia

PARASITIC SYSTEM (grech, parasitos the parasite) — two or several specific populations interacting among themselves in a biocenosis, one of to-rykh are a parasite.

The concept «parasitic system» is formulated by E. Ch. W. Martini in 1932 and further is deeply developed by V. N. Beklemishev.

The item of page is formed population (see) a parasite and all populations of his owners. In structure biocenosis (see) happen double (a parasite — the owner), triple (a parasite — a carrier of a parasite — the owner) and multiple (a parasite — a carrier — several types of owners) parasitic systems. The item of page can be simple when existence of a parasite is provided by one specific population of owners, and difficult if several specific populations — several types of arthropod carriers of a parasite or several species of vertebrate animals — owners (participate in it see. Parazitotsenoz ).

The concept «parasitic system» belongs only to population of a parasite, but not to a look it in general. In different parts of an area the parasite can exist, interacting with population of the owner only of one look or several types, forming respectively simple, difficult P. page.

Processes of interaction of populations of a parasite and vertebrate animals — his owners (P.'s fellow members of page), the causing changes of their number, biol, structure and fiziol, states, are components of epizootic process.

All processes of interaction of population of a parasite with human collective determined by social and biological factors in their set make epidemic process (see). The human population can become a fellow member any P. to page. Simple binomial P. of page arise in that case when at the person activators parasitize antroponoz (see), transferred to it without participation of animals (e.g., a virus of measles — the person; an ascarid — the person). The parasite striking along with the person of population of other types of owners forms complex binomial system on the owner, napr, balantidiya — the person and balantidiya — a pig. Three-membered P. of page happen to participation of the person simple (Provatsek's rickettsia — a louse — the person), but is more often difficult on a carrier (Plasmodium vivax — several types anofeles — the person) or on a carrier and on owners (e.g., P. than page of tick-borne and Japanese encephalitis, a tick-borne spirochetosis).

Value P. of page in a biocenosis consists in regulation of quantitative and qualitative (structural) structure of a biocenosis. Quantitative changes in the ratio of fellow members of a biocenosis are regulated in the main P. by page with high-pathogenic parasites (e.g., causative agents of plague — rodents), qualitative structure (protection against invasion into a biocenosis of fellow members alien to it) — the parasites causing the chronic or asymptomatic course of an infection in animals — owners and a fatal infection in the populations alien for this biocenosis (so, the trypanosome causes a long asymptomatic infection in antelopes, but ruins hoofed animals, foreign to the African savanna, including house).

Practice of development of the low-made habitable territories convincingly demonstrates that disclosure of biocenotic bonds in biocenoses, including bonds in P. the page, is an important condition of rational problem solving of protection and transformation of the nature.

Bibliography: Beklemishev V. N. About the principles of comparative parasitology in use to blood-sicking arthropods, Medical parazitol., t. 14, No. 1, page 4, 1945; Sandpiper And. JI. Main types of functioning of parasitic systems of natural focal infections, in the same place, t. 48, No. 3, page 3, 1979.

A. Ya. Lysenko.