Leptospirosis – common to humans and animals is a dangerous infectious disease that is caused by microbes - leptospires. The disease is accompanied by fever, kidney damage, liver, cardiovascular and nervous system. Leptospirosis in dogs is considered one of the most common diseases. Particularly difficult is the breed with a faulty type of body structure, such as: Neapolitan Mastino, Bulmastiff, English Bulldog, French Bulldog, Boxer, Bologna, Bloodhound, Basset Hound. The disease is most often diagnosed in dogs of hunting breeds, as a result of frequent contact with standing water, as well as in courtyard and stray dogs. Young animals and puppies get sick more often, as they do not have a stable immunity, the hemorrhagic form is more often diagnosed in older dogs. The subject was to study the distribution of leptospirosis among dogs, to establish the seropositivity level and to determine the seroprevalence of the most common of Leptospira serotypes that circulate among this species of animals. For research, an extensive diagnostic series of L. interrogans which includes 20 serovars, and blood serum from dogs that were selected in veterinary clinics in the city of Kyiv, were used as antigen and were transferred to the laboratory of leptospirosis in agricultural animals from the Museum of Microorganisms of the Institute of Veterinary Medicine of the National Academy of Sciences of Ukraine. Studies of blood serum were performed by the microagglutination test (MAT) followed by dark-field microscopy. PMA was placed in 4 dilutions: 1:50, 1: 100, 1: 500 and 1: 2500. According to numerous publications of scientists from different countries of the world, the seroprevalence level of leptospirosis infection among the dogs varies from 39% to 95%. A total of 1831 samples of blood serum were studied in the microscopic agglutination test. As a result of the serological study, 873 animals reacted positively, which is 47.7% of the total number of investigated ones. Analyzing the registered antibody titers, which is most often found titer 1: 100, which is 50.4% of the total number of positive reactions. This indicates the presence of a disease in dogs. Serrogroup Icterohaemorrhagiae is recorded in almost 50% of all positive reactions to leptospirosis and plays a major role in the etiology of the disease. It can be assumed that these dogs had contact with rats or their urine. In turn, the leading for these animals serogroup Canicola was detected in only a third of cases. Other serological groups played a minor role in the etiological structure. Summing up the aforesaid, according to the results of our work, serological prevalence of the pathogenesis of leptospirosis among dogs was determined to be 47.7%. Was detected the circulation of Leptospira`s antibodies in blood serum of these animals. The analysis of the etiological structure of leptospirosis showed that the dominant serogroups were Icterohaemorrhagiae and Canicola. Seven serogroups (Pomona, Sejroe, Grippotyphosa, Australis, Autumnalis, Celledoni, Ballum) were recorded in the range of 1% to 4%. Other serogroups do not have a significant effect on the morbidity of dogs. Keywords: leptospirosis, dogs, etiological structure, serological monitoring, antibody, microscopic agglutination test.

Leptospirosis is an infectious natural-focal disease of many species of animals and human with a wide range of clinical signs. The most common serovars causing leptospirosis in dogs are Icterohaemorrhagiae and Canicola. Analyzing the epizootic situation concerning leptospirosis of carnivores in Ukraine, employees of the Laboratory of Leptospirosis of Institute of Veterinary Medicine of the National Academy of Agrarian Sciences have developed and produced successively three series of bivalent inactivated vaccine against leptospirosis of carnivores, taking into account the etiological structure of the disease of this animal species. The paper presents the results of the study of three experimental series of inactivated polyvalent vaccine against leptospirosis of carnivores regarding: pH, sterility, residual amounts of inactivant, completeness of inactivation, harmlessness and immunogenic activity. It has been established that according to the indicators of sterility, completeness of inactivation, residual amount of inactivant, harmlessness and concentration of hydrogen ions, all three series of vaccine meet the requirements and norms of normative documentation. Intravenous administration of all three experimental series of the vaccine to the experimental rabbits provided the formation of specific anti-leptospirosis antibodies in the titers corresponding to the parameters of the immunogenicity norms established in the technical conditions of the drug.