REPRODUCTION OF PARATUBERCULOSIS IN LABORATORY ANIMALS EXPERIMENTALLY INFECTED WITH <i>M. AVIUM SUBSP. PARATUBERCULOSIS</i> (MAP)
The aim of the research was to choose the optimal biological model of laboratory animals to reproduct paratuberculosis based on dose, way of infection and the age of the animals. Materials and methods. For infection there were selected clinically healthy, not previously reacted to tuberculin (PPD) for mammals and birds, guinea pigs, white mice, rabbits of 1, 3 and 6 months of age. Animals were infected with M.Johnei reference strains and epizootic culture number 5809 selected from cattle. Guinea pigs were intraperitonally infected, rabbits - intravenously and intraperitonally, mice - orally and intraperitonally. Infection of guinea pigs and rabbits was performed twice, with an interval of 14 days at a dose of 2 mg/sm <sup>3</sup>. Oral infection of mice was performed 3-fold, intraperitonally - 2-fold with intervals of 14 days, at a dose of 2 mg / 0.2 cm <sup>3</sup>. The presence of pathological and histopathological changes, as well as mycobacterial colonization of organs (Ziehl-Neelsen's method) was investigated in the intestine, mesenteric lymph nodes, liver and spleen. For histological examination preparations were stained with hematoxilin-eosin. Results. As a result the biological study it was found that the most sensitive to paratuberculosis pathogen are 1-month rabbits. So intravenous and intraperitonally double infection of rabbits 1-month old with reference strains and № 5809 field culture induces histomorphological and pathological changes characterized for cattle paratuberculosis. The most pronounced pathological and histomorphological changes were observed after intravenous infection with № 5809 field culture. At 3-month rabbits induction the characteristic pathological changes was succeeded in 50 % of infected animals, 6-month-old rabbits showed no signs of illness during the entire period of observation. At mice induction the development of acute catarrhal enteritis, lymphoid-histiocytic infiltration of the intestine, desquamation of the epithelium, atrophy of glandulae Lieberkuehnianae and intestinal villi was successfully performed. However, due to the size of the animal pathological changes in mice are less evident, in addition to these animals, unlike rabbits showed no accumulation of macrophages and epithelial cells. Guinea pigs were resistant to paratuberculosis pathogen. Conclusions. The results of postmortem and histological studies suggest that rabbits of 1 months of age, compared with mice and guinea pigs are most susceptible to the pathogen and the optimal model for paratuberculosis reproduction. Intravenous infection with № 5809 field culture induces more pronounced histopathological changes.