Microscopic changes in the spleen due to feline infectious peritonitis

The relevance of the study is that pathological and morphological changes with feline infectious peritonitis have been studied by few authors and are not fully described. The purpose of this study was to investigate the effect of the causative agent of infectious peritonitis on the structure of the spleen in cats. The paper highlights the results of histological studies of sections obtained from distinct parts of the spleen of cats of different ages who died from mixed (26 animals) and dry (7 animals) forms of infectious peritonitis. Sections were stained with haematoxylin and eosin according to the generally accepted method. The paper describes the details of microscopic changes in the spleen in dry and mixed forms of feline infectious peritonitis. It was found that these changes are not affected by the form of the disease but are characterized by features depending on the duration of its course. In cats in which the disease lasted up to three weeks before death, the red pulp of the spleen was unevenly swollen, infiltrated by lymphocytes and monocytes, in some places contained foci of necrotic cells, and red blood cells were absent. Changes in the white pulp were represented by hyperplasia of lymphoid nodules. These nodules were of varied sizes and were located eccentrically relative to the central arteries. There are no distinct lymphoid nodules around part of the central arteries. On the surface of the capsule, fibrinous-necrotic overlays are present in places, under which there is no mesothelium, and the capsule is infiltrated with lymphocytes and monocytes. In other areas, mesotheliocytes underwent distinct metaplasia – from flat cells, they turned into columnar cells. In some areas of the spleen, some animals have no serous membrane. In cats with the disease lasting over three weeks, the red pulp is noticeably more swollen, and the lymphoid nodules are single and small. Other microscopic changes were the same as in animals that were ill for less than three weeks. The results of the study are of practical value for pathologists, as well as for scientists investigating the pathogenesis of feline infectious peritonitis