The distribution of herpes virus infections of the first and second type in tribal horses for the last five years has been established. During this period, a 1301 samples of blood serum samples of horses were investigated in the diffusion precipitation process. Out of these, 412 or 31.6% of the studied specimens were positive for the herpes virus infection of the first type, 473 or 36.4% for the second-generation herpes virus infection, and 345 or 26.5% of the animals were co-infected with herpes virus infections of the first and second type, respectively. The determination of the epizootic situation in the regions shows that the highest percentage of infections with herpes virus of the first and second types is established in Ternopil region, and the smallest in Chernivtsi. In breeding reproducers of the Chernivtsi region, the level of infection of EHV 1 and EHV 2 types does not exceed 10% of the population. We conducted a study on the coexistence of herpes virus infections, leptospirosis and helminthiasis in horses. The results of the coprological research provide an opportunity to state that in all regions the strongilidosis of horses are the most common. Also, frequent cases of infection with dictiocaulosis testify to the grazing of horses on compatible pastures with cattle. The study, based on the latent course of leptospirosis, depending on the severity of the degree of damage by strontium glands, suggests that with a consistent course of leptospirosis and strontium glands increases the number of leukocytes, eosinophils, neutrophils and total protein. In horses positive in the RMA for leptospirosis and free from strontium glands, a decrease in the number of erythrocytes, lymphocytes, eosinophils and an increase in the number of leukocytes, neutrophils and total protein is observed. In the horses positive in the RMA and affected by strontium, there is a tendency to increase the number of red blood cells, leukocytes, and eosinophils. However, it was found that with an increase in antibody titers in the RMA 1:100 and the intensity of invasion by strontials of 100 and more eggs in 1 gram of feces, a significant decrease (P < 0.001) of the absolute number of lymphocytes and a significant increase (P < 0.001) of the absolute number of eosinophils and neutrophils. A significant decrease in the absolute number of lymphocytes in horses with latent leptospirosis with antibody titres of 1:100 in the RMA and the presence of 100 and more eggs in 1 gram of feces may indicate the development of the immunodeficiency state in such animals and the desirability of immediate demyelination.