Pathomorphological changes of the spleen of pigs at different stages of development of clinically expressed PCV2-infection

Cite this article: Evert, V. V. (2019). Pathomorphological changes of the spleen of pigs at different stages of development of clinically expressed PCV2-infection. Theoretical and Applied Veterinary Medicine, 7(2), 126‒132. doi: 10.32819/2019.71022 Abstract. The spleen is an organ that controls the antigenic homeostasis of the blood and provides its filtration. With purpose of determination of pathomorphological changes in the spleen of pigs at different stages of the development of clinically expressed PCV2-infection the comprehensive research was carried out in pig farms of Ukraine, with intensive technology of pig rearing, at the department of normal and pathological anatomy of agricultural animals and the Scientific and Research Center for Biosafety and Environmental Control of the Agroindustrial Complex Resources of Dnipro State Agrarian and Economic University. On the ground of pathological and immunohistochemical studies, the pathomorphological changes of the spleen of pigs at different stages of the development of clinically expressed PCV2-infection have been determined. For pathomorphological studies, animals with clinical signs of active PCV2-infection (in 1 ml of whole blood contained more than 107 copies of the gene, equivalent to the PCV2-virus), as well as piglets with positive optical density of specific antibodies (Ig G and Ig M) in serum blood were selected. It was established, that in the case of clinically expressed PCV2-infection, the spleen had severe symptoms of the disease, the intensity of which depended on the stage of the disease. The stage of early active PCV2-infection is characterized by moderate increase in the macromorphometric parameters of the organ, significant increase in the relative area of the white pulp (at the expense of periarterial lymphoid sheaths and lymph nodules). At the stage of active chronic PCV2-infection, the sharp increase in organometric parameters of the spleen, decrease in the relative indices of white pulp on the background of increase in the area of connective tissue stroma and red pulp are observed. The stage of resolution of PCV2infection is characterized by symptoms of sclerosis of lymphoid parenchyma of the organ. With that its macroscopic and morphometric parameters somewhat increase, but the morphometric indices of the white pulp are minimal, and the indices of the connective tissue stroma are maximal. The development of the infectious process for clinically expressed PCV2-infection is manifested by reactive and acute inflammatory processes in the parenchyma of the spleen. Due to the lymphotropic properties of the pathogen, its ability to be stored in macrophages, the acute inflammatory process is gradually transformed into chronic, and reactive inflammation – into a productive granulomatous type, which is related to immunopathological hypersensitivity reactions of the delayed type.