Virus Reservoir

Virus Reservoir, an animal organism in which a virus of bacterial or protozoan nature nests, and which at the same time is infectious for humans or animals. R. v. can be: 1) organisms for which the virus within them is always non-pathogenic (e.g., African antelopes and the trypanosomes of sleeping sickness), 2) bacilli- or parasite-carriers, for example cyst-carriage in Entam. histolytica, and 3) animals in a state of chronic infection (for example, ground squirrels and the plague virus). For R. v. of the first category, their resistance "to a given virus is a species characteristic, whereas in parasite-carriers a similar property is an individually acquired characteristic. It is not always possible to judge the degree of harmlessness of the virus to its carrier due to the lack of precise observations on wild animals and data on their pathology. Therefore, the category of R. v. is in practice mixed. The epidemiological significance of R. v. can be very significant under certain conditions, since the presence of R. v. in nature leads to the creation of a potential focus of human disease; in fact, such a focus manifests when a person enters the area of distribution of R. v. and in some way receives the infectious agent from it. In particular, thanks to this, infection of a person with this bacterial or parasitic disease can occur in uninhabited areas from R. v. Under other circumstances, R. v. can serve as an additional source of spread of the corresponding disease. The study of R. v. is an important task, since the prevention of diseases they carry in a number of cases cannot be ensured without taking into account the presence and significance of R. v. Among mammals, the following species are known as R. v.: opossums (Didelphys marsupialis) and armadillos (Dasypus sexcinctus, Tatu novemcinctus) - can be infected with Schizotrypanum Cruzi, which is the causative agent of Chagas disease (Brazil), transmitted by the "kissing bug" Triatoma and others; in the blood of African antelopes Tragelaphus spekei there is Trypanosoma gambiense, which causes sleeping sickness in humans, transmitted by the tsetse fly; rodents Lepus campestris and Sylvilagus floridanus in S. America are R. v. of tularemia - Bacterium tularense, transmitted to humans by deer flies Chrysops discalis, ticks Dermacentor andersoni, Amblyomma cajennense and others.; porcupine (Hystrix) can be infected with spirochetes of tick typhus, which infects humans through ticks of various species of the genus Ornithodorus; the vole Microtus montebelloi serves as R. v. of hemorrhagic jaundice (Leptospira icterohaemorrhagiae), seven-day fever - "nanukayami" (Leptospira hebdomadis), river fever - "tsutsugamushi" (carrier - red-bodied tick, Trombicula akamushi) - Japan and others.; the common vole (Microtus arvalis) may be R. v. of rat-bite disease (Sp. morsusmuris); the same is known for the brown rat (Rattus norwegicus - Mus decumanus). The house mouse, brown rat, and black rat can be R. v. of Leptospira icterohaemorrhagiae and possibly Treponema duttoni (causative agent of African tick typhus); ground squirrels, Citellus mollis, C. grammurus and others (North America) are R. v. of tularemia and others. Some rodents, in particular ground squirrels, can be reservoirs of the plague virus, through which humans also become infected with plague. Usually R. v. are considered vertebrate animals, but this is not always correct in essence. For example, it has already been stated that in various rodents there are spirochetes of tick relapsing fever in the blood, transmitted from animal to animal (and to humans) by ticks of the genus Ornithodorus; rodents are therefore considered R. v. of tick relapsing fever. Meanwhile, spirochetes are not always present in their blood. Eventually the spirochetes disappear, and the animal that had them becomes for a certain period immune to new infection. At the same time, the spirochetes permanently remain in the body of the carrier tick and are transmitted by intrauterine invasion to the egg cells of the female and consequently to the next generation of ticks. Thus, it is the ticks, not the rodents, that are the true R. v., but in the epidemiological literature the first interpretation has taken root, which with reservations has to be accepted for general use. The question of the reservoir of the virus, especially among wild animals, has been little studied in the USSR and therefore should be posed as the nearest research task.