Pathogenesis of marble spleen disease virus in ring-necked pheasants (Phasianus colchicus)
Abstract
Marble spleen disease virus (MSDV) produces significant mortality in captive-reared ring-necked pheasants. The natural disease is characterized by splenomegaly and pulmonary edema in birds greater than eight weeks of age. Relatively little is known about the pathogenesis. The present studies were conducted to gain knowledge about the experimental disease. The infection was induced by tissue-culture-propagated virus as a source of pure and quantifiable inocula. The initial study involved oral inoculation of MSDV into 13-week-old pheasants to establish the time-dependent sequence of gross and microscopic lesions. Lesions were limited primarily to the spleen. Many birds developed splenomegaly and microscopic lesions which were most prominent at 6 to 8 days PI. An immunohistochemical staining technique was applied to formalin-fixed tissues to determine localization of viral antigen. Viral antigen was identified in the spleen, lung, liver, kidney and bone marrow. In the next study, pheasants were chemically bursectomized with cyclophosphamide initially administered at one day of age. Bursectomized birds were inoculated with MSDV at 7 weeks of age. Most birds failed to develop typical lesions of MSDV infection. These results suggested the central role of the bursa of Fabricius, or bursal-processed cells, in the pathogenesis of marble spleen disease. In an age-susceptibility study, groups of pheasants at 1 through 6 weeks of age were inoculated with MSDV. Results indicated that pheasants have an innate resistance to the development of MSDV-induced splenic lesions through 5 weeks of age. The final two studies examined the effect of MSDV infection on the immune system. The purpose of the first was to evaluate cell-mediated immunity and measured T lymphocyte transformation in vitro. Transformation was mildly and transiently depressed for 1 week following infection. In the second study, humoral immunity was evaluated by measuring hemagglutination titers to sheep erythrocytes. Titers were significantly suppressed for 6 weeks following infection. These immunosuppressive effects of MSDV infection may have implications with regard to secondary infections and vaccination response.
Degree
Ph.D.
Advisors
Burnstein, Purdue University.
Subject Area
Veterinary services
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