[THE EPIZOOTIC AND EPIDEMIC ACTIVITY OF NATURAL TULAREMIA FOCI OF DIFFERENT LANDSCAPE EPIDEMIOLOGICAL TYPES IN 2009-2014].

OBJECTIVE: to assess the present state of the natural tularemia foci of different landscape epidemiological types, by using individual focal areas as an example. MATERIALS AND METHODS: Epizootological monitoring and epidemiological analysis were conducted in the areas of natural tularemia foci of tundra (Wrangel Island), meadow-field (Central Federal District of the Russian Federation), flood-swamp (Arkhangelsk Region, Khanty-Mansi Autonomous District), and steppe (Mongolii) types. Small mammals (organs, blood), tularemia patients' sera, and environniental objects were examined. Molecular genetic and immune serological diagnostic assays were used. The incidence of tularemia in the past decade was analyzed using the maps for the epidemiological examinations of tularemia cases and medical reports. RESULTS: The natural foci of tularemia were established to continue to actively operate. There were 2913 cases of tularemia in the Russian Federation in 2001 to 2014. The flood-swamp natural foci, in which there were summer transmissive tularemia outbreaks, the largest of high occurred in Khanti-Mansiysk in 2013 when a total of 1005 people fell ill, are a special epidemic hazard. Analysis of the tularemia outbreaks suggests that there is a need for continuous epizootological monitoring of the areas of natural tularemia foci for the timely prediction and prevention of epidemic complications. It is noted that there is an unfounded reduction in the scope of preventive measures, and immunoprevention in particular, and a weaker control of the antitularemia immune status in the population residing in the area of active natural foci of tularemia.

The new vaccine strains (or variants) of Francisella tularensis.

A colony (N83) of the vaccine strain of Francisella tularensis (15/10) and a strain (N268) isolated from a water sample in nature were revealed for susceptibility to cultivation at 42 degrees C. Both strains had low virulence for white mice and were avirulent for guinea pigs but possessed high immunogenicity in these animals. The spontaneous mutant of vaccine strain 15/10 showed resistance to doxicycline and rifampicine (15/10 Dox (r)40 Rif (r)40). The obtained mutant had biological characteristics similar to the parent vaccine strain. It provided immunity in experimental animals when vaccination and antimicrobial agents were used in combination.

Infraspecific taxonomy of tularemia agent Francisella tularensis McCoy et Chapin.

The authors investigated 286 strains of the tularemia microbe isolated in a number of countries of the Old and the New World from humans, hares, rodents, ticks, water and other objects, including 217 strains from the USSR and 69 strains from other countries. As a result, the earlier observed subspecific differences in the biological properties of the tularemia strains isolated in different regions were reconfirmed on an extensive material. It is proposed to designate the three subspecies distinguished within the species as follows: Francisella tularensis holarctica Ols., occurring in the Old World as well as in the New World; F. t. nearctica Ols., known only in North America, and F. t. media-asiatica Aikimb., occurring in Central Asia. Three biological varieties are distinguished in the holarctic subspecies: biovar japonica Rod., occurring on the Japanese islands, biovar I eryS (erythromycin-sensitive) distributed in Old and New World and biovar II eryR (erythromycin-resistant) known only in a few localities in Europe and Asia. Subspecific taxons differ from each other in several stable signs including biochemical-fermentation of glycerol and citrulline, and others, in the degree of pathogenicity for man and domestic rabbits, in the ecology and also in the area of distribution while the biovars differ in one sign and partly in the area of distribution. No differences were found between the North-American strains of the holarctic subspecies and the Eurasian holarctic strains of biovar I. The absence of serological differences between the individual taxons is no obstacle to infraspecific taxonomy of the tularemia microbe.

Detection of enzootic territories and exploration of tularemia epizootics in different types of natural foci of this infection by serological examination of bird pellets and the excrements of beasts of prey.

Serological analysis (reaction of antibody neutralization) of pellets of birds and excrements of beasts of prey for the presence of tularemia microbe antigen is an efficient method of detection and investigation of epizootics in all types of natural foci of the infection and also for the exploration of new focal territories. The method permits with small expenditure of labour and within a short time, to collect material characterizing the epizootic process on a large territory. Tularemia epizootics, both having taken place in the past and ruinning at the moment of observation, are detected. It is possible to carry out the observations even in the years of a reduced number of the main carriers of the agent of tularemia and thus to trace the continuity of the epizootic process. The obtained data permit to establish the essential characteristics of the epizootic process. Detailed maps of the foci can be drawn and territories of stable preservation of infection detected.