POST-VACCINATION IMMUNITY IN ARCTIC FOXES VACCINATED AGAINST SALMONELLA

Abstract

Combating salmonellosis has always been an important task. This infection has been widespread among farm and fur animals, as well as poultry, and tends to be on a rise lately. Furthermore, 85 % of animals continue to carry the bacteria after recovery. Salmonellosis outbreaks are registered among fur animals from early April to late September. In some farms, mortality is up to 30 %. As a result, epizootic hotbeds of salmonella infection are persistent. It is therefore important to take timely and specific actions to prevent, reduce and eliminate animal losses to salmonellosis. The inactivated salmonellosis vaccines used until lately proved to be not very effective. Vaccination of animals induces complex structural and functional changes in the immune system organs. Repeated administration of the drug, as instructed, turns immunization into a lengthy and laborious process. This study was carried out with cage-reared Arctic foxes treated with inactivated vaccine. Animals in the experimental group were vaccinated with an associated inactivated vaccine against colibacillosis, salmonella, klebsiella and protozoa infections manufactured by the Pokrovsky Biologics Plant and LLC AgroVet (vaccine OKZ TU- 9384‑047‑00008064‑99). The animals were vaccinated subcutaneously twice with an interval of 14 days according to the instruction for the drug. Animals in the control group were not vaccinated. After the scheduled slaughter of cage-reared Arctic foxes, 5 animals from each group in their 7th, 14th, 21st, and 28th days after vaccination were taken. Their spleens and submandibular lymph nodes were extracted for histological examination and fixed in 10% aqueous solution of neutral formalin. Cellular immunity was assessed using opsonophagocytic assay (OPA), E- and EAC-rosette formation, and agglutination test. Morphological and morphometric measurements of the peripheral immune organs were taken. Spleen tissue sections from vaccinated Arctic foxes had red and white pulp clearly visible during histological examination. Histological examination of mandibular lymph nodes of the Arctic foxes revealed primary and secondary lymphoid nodules in the cortical layer. Medullary cords are thickened due to the accumulation of lymphocytes. Immunization of Arctic foxes with inactivated vaccine against salmonellosis results in the proliferation and differentiation of immunocompetent cells in peripheral immune organs, which involves an increase in the number of immunoblasts and mature plasmocytes. This change is characteristic of both cellular and humoral immune response.