From Big Medical Encyclopedia

CARRIERS — the backboneless animals (most often blood-sicking insects and mites) who are intermediaries by transfer of causative agents of diseases from the person to the person from an animal to the person or from an animal to an animal.

Transfer of activators carriers can be mechanical and specific. In the first case the activators which got to P.'s organism can remain a nek-swarm time, without breeding, and then carriers are mechanical (nonspecific), or, in the second case, to pass in it a certain phase of a life cycle, and then call them specific carriers.

If the disease-producing factor (e.g., a malignant anthrax or a tularemia) remains on oral parts of the bloodsucker (a gadfly, a mosquito, etc.), then transfer is carried out at the sting which is followed by introduction to fabrics of the oral device P. contaminated by the activator (inoculation). Such inoculation is called nonspecific. A number of activators (e.g., causative agents of intestinal infections or viruses of epidemic conjunctivitis) can remain on a body surface of insects (or in their intestines) and then to be transferred to mucous membranes of the susceptible person, objects of use or food, contaminating them (contamination). In the described case it is about mechanical (nonspecific) contamination.

Getting to an organism of a biological (specific) carrier at a krovososaniye transovarialno (through eggs of the infected parents) or transfazovo (through their larvae or nymphs), the activator breeds, collecting in bodies or fabrics, or develops in them, reaching invasive (i.e. capable to be transferred) a stage of development. Accumulation of the breeding activators can happen in P.'s intestines, napr, bacteria of plague at fleas; in cells of an epithelium of intestines, napr, rickettsiae (causative agents of a typhus) at louses: in a wall of intestines, napr, plasmodiums of malaria. In a perigastrium and sialadens there is a reproduction of an arbovirus (at mosquitoes and mites) and rickettsiae (at mites). Roundworms (filarias) do not breed in P.'s organism, but, having passed through intestines and having got to a perigastrium of P., develop and reach a stage at which can be transferred to other organisms at a krovososaniye.

The majority of activators is transferred by specific carriers at a sting (krovososaniye) — specific inoculation. With saliva of a carrier an arbovirus, rickettsiae, sporozoita of causative agents of malaria, from front departments of intestines with current of saliva — promastigota of leyshmaniye and a trypanosome etc. are transferred.

Hit of activators in an organism of owners happens in some cases by pollution of mucous membranes or the injured skin allocations (excrements or the crushed fabrics) of specific carriers — specific contamination. By such way trypanosomes (disease-producing factors of Shagas) and a rickettsia — causative agents of a typhus are transferred.

The diseases transferred by arthropod P. depending on a source of an infection share on antroponoza (see) and zoonoza (see). In the first case the only source of the activator is the person (e.g., at malaria), in the second — an animal (at a malignant anthrax). The majority of zoonoz are natural focal infections [see. Natural ochagovost (diseases) ]. The role of various blood-sicking arthropods in epidemiology of these infections is not identical. Only the small number of types of P. matters in transfer of activators to the person. The most part of types carries out transfer of activators from one animals another. A part of types plays a role in preservation of activators during the interepizootic period by transfer to their posterity. Transovarial and transphase transfer of rickettsiae by mites and an arbovirus — many species of mosquitoes is established (see. Transovarial transfer , Transphase transfer ). Some activators are transferred only by blood-sicking arthropods — so-called obligatory (obligate) carriers; these are causative agents of obligate and transmissible infections (e.g., malaria, a skin leushmaniosis). Other activators can be transmitted or through a sting (krovososaniya) of optional (optional) carriers, or other ways (e.g., Ku rickettsios activator can be transmitted as through a sting of the infected mites, and an air and dust way).

Studying of biology of P. is necessary for the organization of fight against them. It includes determination of speed of development of P., number of generations, durations of existence of separate phases, abilities to transfer or preservation of activators on different phases of development, resistance to influences of various environmental factors, places of concentration, distribution to territories of the center in space and in time etc. In particular, it is shown that fight against the inspired midges (carriers of an onchocercosis) owing to their distribution on huge spaces and distant flights is absolutely inexpedient whereas destruction of larvae in rather small amount of reservoirs where there is their development, is possible by means of a small amount of insecticides. Fight against carriers of malaria is conducted by processing of walls of rooms where they usually are in the afternoon, is long operating insecticides (see). The only means of mass nonspecific prevention of a tick-borne encephalitis is processing of the territory of the center near dwellings of the person resistant contact insecticides. In places of contact of the small contingents of people with estimated carriers use of protective clothes is reasonable (see. Clothes special ) in a combination with repellents (see). Fight against aqueous phases of development of blood-sicking flies (their larvae) is carried out by use of chemical insecticides, inhibitors of development of insects (e.g., an analog of juvenile hormone of a metopren), predatory lichinkoidny fishes (gambuziya, etc.) and other means of biological control. Bacteria, pathogenic for insects, fungi, viruses and the elementary organisms are studied and find application. Those are most perspective among them, to-rye will not only lead to reduction of number of carriers, but also to oppress them ability to perception and transfer of causative agents of diseases of the person (see. Biological methods of controlling ).

Certain representatives of carriers — see independent articles: Fleas , Louses , Midges , Rodents , Mites , Flies etc. See also Mechanism of transmission of infection .

Bibliography: Alekseev A. N. The main directions of researches for fight about the infected blood-sicking mites and insects — carriers of diseases of the person, Parasitology, t. 13, No. 3, page 185, 1979; B of e to l of e of m and sh e in V. H. Biocenological fundamentals of comparative parasitology, M., 1970; P and in l about in with to and y E. H. Guide to parasitology of the person, t. 1 — 2, M. — L., 1946 — 1948; Parasitology of the person, under the editorship of G. S. Pervomaysky and V. Ya. Podolyan, JI., 1974; T and r and with about in V. V. Arthropod carriers of causative agents of diseases of the person, M., 1981.

A. N. Alekseev.