The varying extents of natural disease induced by coronavirus in dogs are not completely clear because the pathogenesis of coronavirus enteritis is not studied sufficiently. In this study, based on the results of clinical, virological, morphological and histochemical studies, we determined the pathogenic role of coronavirus in infected dogs using experimental infection, per os, of isolated canine coronavirus (Nick) with titer of infectious activity equaling 4.8 ± 0.04 lg TCID50/cm, cultivated on heterologous cell cultures. This allowed us to determine, supplement, and generalize the data on pathogenesis of the disease and determine the histological changes in the small intestine, where the initial replication of the pathogen takes place. It was found that lesions and the pattern of the pathomorphological changes (destruction, necrosis and edema of the stroma of the villi, lysis of the cytoplasm, deformation of the enterocyte nuclei) in the small intestine of experimentally infected dogs depend on the development of the pathological process related not only to the changes in histoarchitectonics of the wall of the intestine, but also to tension of the histochemical statics, and obviously the dynamic of the cells (accumulation of the main and acidic proteins in enterocytes’ cytoplasm, hypersecretion of the mucus by goblet cells, decrease of Schiff iodine acid-positive substances in the enterocytes’ cytoplasm, formation of basophilous inclusion bodies), which leads to disorders in metabolic processes in the organism of infected dogs as a response to the virus infection. The examined dogs were found to have morphological changes in the small intestine similar to those in spontaneously infected animals. During the action of coronavirus, the contacts between the enterocytes become damaged, which leads to inhibition of the protective functions of the intestine. At the same time, the pathological process in the experimentally infected animals developed rapidly and had an acute course. Thus, coronavirus enteritis as a separate disease is practically unobserved in field conditions, which makes microscopic survey of the pathogenic impact of the latter on the organism of dogs impossible. Therefore, experimental mono-infection allows a detailed study to be conducted of pathomorphological changes of the initial place of the reproduction of the virus – the small intestine affected by coronavirus enteritis.

The article presents the results of studies of erythrocytopoiesis in horses with herpesvirus infection of the first type (rhinopneumonia) and respiratory manifestations of herpesvirus of the second type and their coexistence in animals. In the general pathology of horses, herpesvirus infections of horses occupy a leading place, and diseases of mixed etiology, which occur with atypical manifestations of clinical signs, are of particular concern. The work was performed in 2018 on the basis of the laboratory of the Department of Microbiology, Pharmacology and Epizootology of Polissya National University on breeding horses belonging to the Nahiryan branch of PJSC "Rise-Maximko" Ternopil region. Blood for the study was taken from the jugular vein against Jugulares in the morning before feeding Diagnostic studies to confirm herpesvirus infection were performed in the reaction of delayed hemagglutination, reaction and diffusion deposition - for herpes of the first type and in the reaction and diffusion precipitation to herpesvirus infection of the second type. Evaluation of erythrocyte indices allows you to get an idea of the characteristics of erythrocytes, which is very important in determining the type of anemia. Erythrocyte indices often respond quickly to the treatment of anemia and can be used to assess the effectiveness of therapy. The studies revealed a significant decrease in the number of leukocytes P ≤ 0.05 in animals of all experimental groups. Regarding hematocrit and erythrocyte counts, a significant decrease in P ≤ 0.05 was found in horses affected by EHV-1, and in the case of coexistence of two types of pathogens - a significant decrease in P ≤ 0.01. Erythrocyte index indices for herpesvirus infection of the first type in horses were characterized by a significant P ≤ 0.05 increase in the mean hemoglobin concentration in erythrocytes and a significant P ≤ 0.05 decrease in the mean erythrocyte volume. In herpesvirus infection of the second type, the fluctuations of the indices were not significant. In the combined course of the two types of viruses in horses, a significant increase in P ≤ 0.05 hemoglobin content in one erythrocyte and a significant P ≤ 0.05 increase in the average volume of erythrocytes.

The article, based on the results of histological studies, presents data on the microscopic structure of the immune system – thymus, spleen, lymph nodes of dogs with experimental infection with coronavirus enteritis. Pathomorphological studies of immunocompetent organs from the dead (n = 5) puppies crossed Labrador breeds with outbred, infected with a coronavirus field isolate cultured on heterologous cell cultures (kidney kidney hamster (BHK-21), rabbit kidney (RK-13) and the renal mumps (SPEV). Pathological dissection of dogs was performed by partial evisceration in the usual sequence. Prepared histological sections were stained with hematoxylin and eosin according to standard recipes. The general histological structure and microstructural changes of histo- and cytostructures of organs in histological samples were studied under a light microscope. During coronavirus enteritis in dogs, pathomorphological changes in immunocompetent organs were found, which characterize the suppression of immunogenesis function during an infectious disease of viral etiology. Thus, in the spleen there are spotted hemorrhages, lymph nodes, moderate hyperplasia, with signs of hemorrhagic inflammation. Active proliferation of lymphoid cells, which leads to hyperplasia, is one of the markers of the pathogen's effect on the macroorganism in the form of an inflammatory process in regional lymph nodes, which indicates the multiplication of the virus and the development of immunological processes. Based on our analysis of literature sources, monitoring results and our own research, it was found that viral enteritis occupies a leading place in the infectious pathology of dogs and causes significant harm to animal owners. Thus, the need for additional research to clarify, supplement and summarize data on the pathomorphology of various organs and tissues in canine corona viridae enteritis, current immunoprophylaxis and treatment can significantly reduce the incidence and mortality from infection. We found a set of histological changes in the immune system during the experimental reproduction of coronavirus infection, can be considered a characteristic criterion for pathomorphological differential diagnosis of coronavirus enteritis in dogs.