RODENTS (Rodentia) — group of a class of mammals; are morphologically characterized by strong development of the cutters, in a form reminding a chisel, lack of canines and a fold surface of molars. The mandible can move forward and back and in both parties that in combination with a shape of molars promotes the best mastication of vegetable food. On these signs in a systematics allocate the cohort (superorder) of Glires combining group actually of rodents (Rodentia) and group of zaytseobrazny (Lagomorpha). Being tank of a contagium (see) and carrier (see) various diseases of the person, have great medical value.
Are known to mankind since the most ancient times. In chronicles and oral legends of many nationalities of the world there are references of mass emergence of G. which received the name «mouse misfortunes» which were followed by hunger and a serious illness of people and domestic animals. Are used as sources of meat, fat (gophers, groundhogs, Guinea pigs, nutrias); since the beginning of the XX century worldwide in connection with destruction of valuable types of fur-bearing animals mass types of minor furs began to trade, and G. by quantity of the made skins won first place.
Laboratories of the world are used as experimental animals of 38 types of wild G. during the studying of infectious diseases, in oncology, toxicology, surgery, genetics, ecology, etc. Some types of G. contain as decorative animals (a squirrel, a chipmunk, an Asian hamster).
The group of zaytseobrazny is not numerous and includes only 63 look united in two families of hares and one family of creepers; differs in two couples of cutters in an upper jaw (dvuparnoreztsovy).
Actually G. — the most numerous group in a class of mammals. According to modern data, it consists of 1687 types, 34 families (42,5% of types of a class of the mammals) widespread on all continents of the world. Distribution of types in group unevenly: families of hamsters (567 types), mouse (457 types) and squirrel are richest with types (including willows of the USSR) (261 look) [according to S. Anderson et al., 1967].
More than 2/5 types of G. — small forms (it is powerful from 5 to 500 g). A short life cycle and a bystry ontogeny, frequent digenesis, high rates of evolution and speciation are characteristic of them. Large forms — with longer life cycle, have a smaller specific variety (hares, beavers, porcupines). Separate types of G. are presented on tsvetn. fig. 1 — 20).
— the most prolific animals among mammals. Many of them potentially can breed all the year round and under natural conditions the number of a dung reaches to 4 — 7 in a year. Early approach of puberty (at the age of 1 — 2 month), a continuity of reproduction create conditions for bystry increase of number and rather high level of density of their settling.
Almost everywhere prevail among hematothermal (mammals and birds) not only on number of individuals, but also on biomass per acre.
The specialized forms adapted for an underground, wood or okolovodny way of life occur among G. There are among them no purely water and flying forms, and ground mass is made by semi-underground — nornik, the semi-wood, semi-water and land activities having high ecological ductility, adapted to exist in various vital niches (see. Ecology ). Plasticity is shown also that along with the specialized forms G. living only in certain biotopes (e.g., jerboas, etc.), many types mastered various biotopes and widely meet within landscape zones on plains (plakor) and in mountains. G.'s types of interzonalny landscapes (the floodplain of the rivers and lakes, the swamp, meadows, riparian forests and other options of the landscapes of the increased moistening called by also littoral landscapes) — are most eurysynusic in the USSR and deeply get from one zone into another.
The ground mass of G. — geterotermny animals (see). Their behavior is directed to maintenance of constant body temperature: a big physical activity, plentiful food, close accumulation of little wild beasts in shelters. The most important feature of biology of G., from a cut many parties of their life activity depend — creation of own microclimate in various weather conditions (so-called ekol, thermal control). For this purpose in the closed landscapes (a forest zone) G. use numerous natural shelters: create nests in bushes and on trees at various height; in littoral flooded G.'s landscapes do difficult underwater and surface constructions — lodges or nests, in mountains of a nest settle in stony scatterings and rocks, and on open landscapes dig holes of various depth. Holes of groundhogs, gophers and sandworts are most difficult and long-lasting. Radio-carbon datings of holes showed that at some types they exist up to several millennia (at a groundhog — to 10 thousand years, at a long-tailed gopher — to 3,5 thousand years).
Parasites are inhabitants of nests and holes — differ morphologically and ecologically from other land parasites — the pastbishchnik connected with places of getting of a forage by the owner. In places of the increased moistening the parasites connected in the origin with an aqueous medium meet.
3 types of the parasitic systems connected with G. are respectively allocated: ubezhishchny, pasturable and littoral. So, the ubezhishchny type of parasitism is characteristic for the sucker, mosquitoes, many species of gamazovy, argasovy and some ixodic mites, pasturable — of many ixodic mites; littoral type — for mosquitoes, larvae of some species of krasnotelkovy mites, separate species of fleas and gamazovy mites, and also for endoparasites (especially trematodes). All these groups of parasites are found in G. Zaytsa, unlike G., have no ubezhishchny parasites, but on pastures they possess the leading role in pro-feeding of adult phases of ixodic mites that provides a possibility of reproduction of the last. On the contrary, on G.'s pastures the role of additional owners — prokormitel of larvae and nymphs of mites or intermediate owners of some helminths belongs (alveokokk).
G.'s parasites are studied as carriers of diseases and as indicators of trans-species bonds and a confinedness of owners to certain options of a landscape. Comparative parazitol. the method allows to estimate not only parasitic systems of arthropods, but also bonds of a parasite and the owner on the example of causative agents of zoonotic infections (see. Zoonoza ). Studying of parasites of G., shows that along with three specified groups of the parasites living in natural landscapes the parasites who are constantly living in settlements of the person meet (e.g., synanthropic species of fleas, gamazovy, argasovy mites) that reflects close connection of G. with activity of the person.
Existence of many types of G. is inseparably linked with various forms of human activity. Anthropogenous landscapes resulted from development and transformation by the person of natural landscapes.
Development of natural landscapes is connected with use of natural resources (page - x., forestry and landscape and other forms of activity), mass production of G. for laboratory and other types of researches. In these cases there are no considerable qualitative changes as a part of G. and there are only some quantitative changes (e.g., seasonal concentration of G. in ricks of hay, on haymakings in forest belts, on cutting areas and cuttings down * roads and pastures of the cattle).
Transformation of the surrounding nature (creation of economic grounds with jump of primary natural landscapes and first of all a vegetable cover) exerts impact on qualitative structure of fauna: one types disappear, appear and others dominate. In that case when around the transformed landscapes primary natural stations remain, there is a creation of the mixed G.'s populations — lesopolevy, lugopolevy, steppe and field, desert and oasitic, etc.
Some types of G. expanded the area in connection with field husbandry and began to dominate (e.g., an ordinary vole, a hamster, a field mouse, a hare hare — so-called obligate antropofila). Possess an extreme form of adaptation to activity of the person synanthropic animals (see) — the few types of G. occupying settlements, surrounded with strongly transformed landscapes.
Antropofiliya G. as a result of their high ekol, is expressed to plasticity in huge variety of G. as carriers and sources of causative agents of diseases of the person.
In total in the USSR the carriage of causative agents of diseases of the person at 98 of 144 types of is established. Total quantity of intermediate owners (fleas, mites, etc.) is equal to 743. Thus, the average value of a natural susceptibility of G. (EV) is equal to 5,2 (743/144). The name of an indicator of EV — a natural susceptibility — is connected with the fact that during the calculation of this indicator not only direct allocation of the activator, but also indirect indicators of existence of contact of this type of G. with the activator in nature are considered (see the tab.).
The indicator of EV can be used for comparison purposes potentialitys of various groups of animals in infectious pathology of the person. E.g., at G. it is 2 — 3 times higher, than at other groups of mammals and at birds. The highest rates of a natural susceptibility are noted at G. - sinantrop (a rat gray, a mouse house) and field G. (a field mouse, a vole ordinary), i.e. the types characteristic of anthropogenous landscapes. According to it allocate 2 groups • the centers connected with G. — the centers of anthropogenous landscapes and the natural centers (see. Natural ochagovost ).
In anthropogenous landscapes existence of the centers of diseases of the person in many respects is defined by his converting activity. This form of activity of the person leads to disturbances of patterns of existence of natural biocenoses that is shown in features of the anthropogenous centers of diseases. Year-round manifestation epizootic, and together with it and epid, processes, a possibility of existence in various climatic conditions is characteristic of the majority of these centers. At the same time seasonality of manifestations and territorial distribution (ochagovost) are in direct dependence on various forms of activity of the person. The main carriers in these centers or exist irrespective of natural biocenoses, or their populations are connected with surrounding natural biotopes. Respectively allocate two groups of the centers — the independent (urbanichesky) and dependent (antropurgichesky) centers.
In the urbanichesky centers the main carriers are G. - sinantropa (gray, black, places Turkestan rats and a house mouse). Therefore sometimes these centers call synanthropic. However the concept «urbanichesky center» reflects their essence more precisely: constant and independent existence in city conditions; detection them in rural settlements should be regarded as the secondary phenomenon.
Simultaneous existence of all three types of parasitic systems — ubezhishchny, pasturable and interzonalny is characteristic of the urbanichesky centers (littoral). The typical urbanichesky centers are characteristic of a limfokhoriomeningit, rickettsioses, a pseudotuberculosis, to a sodok, leptospirosis. Besides, G. - sinantropa in these centers are additional carriers and sources of causative agents of plague, salmonelloses, an erizipeloida, leptospirosis, etc.
Epizootic processes are usually observed all the year round without jumps of their intensity by years that it is connected with a limited possibility of reproduction of G. in city conditions. G.'s distribution in the city has focal character and is defined in many respects by economic activity of the person, as a result a cut the steady centers of the raised G.'s number at the enterprises processing agricultural products on public food objects, in private apartments and even in certain rooms are created. Respectively and epid, manifestation of the centers is limited to sporadic and isolated cases and as an exception, local flashes.
The major epidemiol, feature of local flashes in the urbanichesky centers is transfer of the activator in the aerogenic way. The prevailing number of diseases in these centers is connected with alimentary or the alimentary waterway of infection. Cases of single diseases as a result of these or those G.' sting are known (e.g., rats, proteins etc.).
The Antropourgichesky centers are connected with page - x. activity of the person in various landscape zones; characteristic options of these centers are the lesopolevy, lugopolevy, steppe and field and oasitic centers with the major carriers — voles ordinary and Far East and mice (house, field and forest). Qualitative difference of these centers is periodic high intensity epizootic and epid, processes as a result of creation by the person of favorable conditions for intensive (sometimes year-round) reproduction, i.e. sharp rises in number of. Such anthropogenous landscapes represent wildlife reserves of carriers from where they come to settlements (and back — to natural biotopes). Historically these centers were shown in the territory of the USSR the largest epid, flashes of a tularemia in the lugopolevy and steppe and field centers at late thrashing (sources — a house mouse and an ordinary vole).
In the steppe and field centers mass resettlement of house mice from fields to settlements was the cause of large epidemics of a tularemia and plague. In the lesopolevy centers the similar local outbreaks of diseases are characteristic of hemorrhagic fever (sources — a field mouse and the Far East vole). Communication with page - x. by works it is established for diseases of leptospirosis in the oasitic centers (sources — mice) and the steppe and field centers adjoining on boggy ravines and forest splittings (sources — voles). Cases of a tularemia (trade of hamsters, hares), by leptospirosis and fungal diseases in animal-breeding farms are described (sources — a nutria and a muskrat).
Existence of domestic animals in this connection many causative agents of the diseases of the person which are widely found at these animals are found in G. - sinantrop and G. - antropofil is closely connected with anthropogenous landscapes (A Q fever, paratyphus, a malignant anthrax, a brucellosis, erizipeloid, listeriosis, Toxoplasmosis, etc.).
Historically bystry emergence and disappearance in connection with change of forms of economic activity of the person is characteristic of the anthropogenous centers. In particular, creation of conditions of «krysonepronitsayemost» at construction of the new cities, and also mechanization of harvest works in agriculture promote sharp reduction of number
of G. Odnako special attention should be paid on possibility of the anthropogenous centers at flood of droughty areas, creation of forest belts and other measures of development of agriculture.
The natural centers of diseases of the person are connected with the interzonalny, zone and mountain landscapes to some extent mastered by the person. Characteristic options of the centers of interzonalny or littoral landscapes with the increased moisture content are inundated, marsh and tygai options in combination with meadows. The main carriers in these centers — a water rat, a muskrat, voles — the housekeeper and east, mice — field, house and the baby, places a gray rat and all three species of hares. These types of G. provide existence of the centers of a tularemia, leptospirosis, a dicrocoeliosis, the Omsk hemorrhagic fever and, perhaps, fevers of a tsutsugamusha. Their distinctiveness is close connection with biotopes of the increased moistening and respectively their arrangement in lowlands of a relief. On these valley and depressive landscapes the centers of diseases get from one landscape zone into another.
The tularemia and leptospirosis are widespread in the USSR from a zone of the tundra to a zone of deserts; for leptospirosis this feature is observed on all continents of the world; spread of fever of a tsutsugamusha outside the USSR takes several climatic zones up to Australia.
The distributional pattern of diseases well reflects potentialitys of the main carriers. G.'s types connected with interzonalny landscapes owing to the plasticity easily master plakorny landscapes, especially in connection with their anthropogenous changes. According to causative agents of diseases and their centers pass from interzonalny into plakorny anthropogenous landscapes, and is not accidental that the tularemia and leptospirosis are at the same time leading forms of diseases of anthropogenous landscapes.
The zone centers of diseases of plains of the USSR are characterized by a big variety of landscape options and the main carriers and sources of diseases among G. Vydelyayut the forest centers and the centers of open landscapes (desert and steppe); in the tundra the zone centers are not established, and only interzonalny are known.
The main carriers in these centers concern to group G., specifically connected with many zone biotopes. Owing to such specifics they are less adapted for reformative activity of the person. At the same time to the landscapes mastered by the person, in particular to pastures of domestic animals or to places of forestry and landscape activity, these types of G. are adapted better than other zone forms and can be called zone and anthropophilous forms.
Other feature of the zone centers — communication of causative agents of diseases with soils, an accurate razgranichennost of pasturable and ubezhishchny types of parasitism and in this regard accurate distinctions of the main carriers among G.; the pasturable centers are connected with hares (G. are additional carriers), the ubezhishchny centers are connected with G. (hares are additional or minor carriers).
The pasturable centers of a tick-borne encephalitis and tularemia and presumably ubezhishchny centers of hemorrhagic fever are characteristic of forest options of the zone centers.
The role of the main carriers in the pasturable centers belongs to animals, prokarmlivayushchy adult phases (imago) of ixodic mites. As prokormitel of larvae and nymphs possess a role of additional carriers — disseminator of a virus. The epidemiology of these diseases is connected with production forestry and landscape activity, and also with visits of the wood (collecting mushrooms etc.). The pasturable centers are not connected with settlements while more frequent infection not under production conditions (in the wood), and in forest settlements is characteristic of ubezhishchny hemorrhagic fever (i.e. household infections).
The forest centers, as well as all zone natural centers, have strict seasonality in manifestation and limitation (endemicity) in distribution. Activity of the person can exert a nek-swarm impact on their activity, causing an intensification or, on the contrary, attenuation of the centers.
In open landscapes the pasturable centers of the Crimean hemorrhagic fever, a tick-borne sapropyra, a tularemia and the ubezhishchny centers of plague, a skin leushmaniosis, etc. are known. The principles of existence of these centers are similar to above described: in the pasturable centers the main carriers — hares, in ubezhishchny — gophers and sandworts.
The hole created by the digging activity of the owner as the elementary center, historically became the first criterion at allocation of the main carrier, and a small gopher and a big sandwort — the first objects of researches. Thanks to intensive norovy activity and relative stability of number they come to the forefront in biocenoses of open landscapes, as defines their role as main carriers in all centers of infections of these landscapes.
The main carrier — the owner of the center, its life activity exerts impact on all epizootic processes happening in a specific landscape including and on development of an epizooty in population of additional owners. The last owing to the high susceptibility promote wide dissimination of the activator even out of limits of the center and in this regard most often are sources of infection of the person.
The Ubezhishchny centers and in this zone have feature «to get» into settlements, forming the synanthropic centers included in this landscape (e.g., the centers of a city skin leushmaniosis, and abroad — plagues).
The epidemiology of the centers of open landscapes is defined by many forms of activity of the person: trade of gophers, groundhogs and hares (plague, a tularemia), page - x. activity (plague; a source — a sandwort), and also various cases of household infections with a tick-borne spirochetosis, a skin leushmaniosis on farms and in the settlements surrounded with primary natural stations. Of these landscapes are also minor and additional carriers of the activators connected with domestic animals (see).
In mountain landscape options of the centers causative agents of many «flat» diseases are found in G. Diseases, specific to these landscapes, it is not established. A peculiar mixing of «flat» diseases in mountains is explained by the altitudinal zone zonality where at the same height desert and forest forms G. therefore the virus of a tick-borne encephalitis is found in types of open landscapes, and plague — in forest Forms can meet. At the same time potentialitys of the mountain centers are low: from 47 mountain species of rodents of fauna of the USSR causative agents of diseases of the person are not found in the 19th.
Conditions of infection changed. Despite intensive housing construction, manifestation of the urbanichesky centers was sharply reduced. However process of an urbanization promotes increase in contacts of urban population with the natural centers in connection with mass participation in page - x., construction works, and also as a result of mass tourism, other organizational forms of rest and intensive gardening activity around big cities. Development of the new territories provided by development of the national economy of the country also increases relative value of natural landscapes in pathology of the person. Development medico-biol. researches of various profile with mass use of wild G. as models creates premises for vivarny respiratory infections.
Active measures of prevention of a mass epizooty and opportunities of infection of people are under construction in two directions: restriction of favorable conditions for G.'s existence and prevention of emergence of places of their increased concentration and direct destruction of G. various means (see. Deratization ).
NATURAL CARRIAGE of CAUSATIVE AGENTS of DISEASES of the PERSON MAIN REPRESENTATIVES of GROUPS of RODENTS AND ZAYTSEOBRAZNYKH of FAUNA of the USSR.
The table includes species of rodents and the zaytseobrazny, studied in the USSR on a spontaneous carriage various causative agents of diseases of the person, a condition and mechanisms of infection of the person; for these types distribution, types of habitats and shelters, communication with activity of the person are specified. The arrangement of separate types of G. is given according to the existing international classification of mammals. For taxons of higher ranks (a superfamily, family, group) after the name number of types to the USSR, total number of carriers (the sum of causative agents of diseases of the person, including their options) and the indicator of the natural susceptibility («NS») representing private from division of total number of carriers into total number of types of this systematic group (group, family) in the USSR are given total quantity of types in the world, distribution on continents. In the table abbreviations are accepted: In — the carriage established by direct allocation of activators it is gray — serological.
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