ARS | Publication request: Comparison of the pathogenicity of Chinese and low virulent US porcine reproductive and respiratory syndrome viruses

Submitted to: American College of Veterinary Pathologists Meeting
Publication Type: Abstract Only
Publication Acceptance Date: August 19, 2011
Publication Date: November 1, 2011
Citation: Henningson, J.N., Faaberg, K.S., Guo, B., Schlink, S.N., Miller, L.C., Kappes, M.A., Kehrli, Jr., M.E., Brockmeier, S.L., Nicholson, T.L., Vorwald, A.C., Lager, K.M. 2011. Comparison of the pathogenicity of Chinese and low virulent US porcine reproductive and respiratory syndrome viruses [abstract]. American College of Veterinary Pathologists. Paper No. 164. Veterinary Pathology. 48(6):E30.

Technical Abstract: Recently, a new strain of porcine reproductive and respiratory syndrome virus (PRRSV) has resulted in huge economic losses in the Chinese pig industry. We imported a cDNA clone of the rJXwn06 Chinese strain from which infectious virus was obtained to test the hypothesis that the novel Chinese PRRSV strain would not induce severe clinical disease and pathology as seen in Asia when inoculated into U.S. high-health swine. Under ABSL3 biocontainment following NADC IACUC guidelines, 10-week-old swine were infected by intranasal inoculation with either 2 ml of 10**6 TCID50/ml rJXwn06 (n=12 challenge, n=4 contact) or the North American prototype strain VR-2332 (n=8), or a sham inoculum (n=8). On necropsy consistent findings were severe thymic atrophy, lymphadenopathy, and extensive interstitial pneumonia in the Chinese PRRSV inoculated pigs; these lesions were not as severe in the VR-2332 inoculated group and were not present in the sham inoculated pigs. On histopathology, a majority of Chinese PRRSV inoculated pigs had more severe and extensive, lymphoid depletion, interstitial pneumonia, lymphohistiocytic perivascular meningoencephalitis, myocarditis, and interstitial nephritis as compared to the sham and VR-2332 inoculated pigs. Bacterial co-pathogens likely played a contributory role to development of lesions in Chinese inoculated pigs. Immunohistochemistry labeled PRRSV antigen in pulmonary macrophages in both the Chinese and VR-2332 inoculated pigs. Preliminary results confirm that the Chinese PRRSV is a virulent virus that could be a threat to the US swine industry. Further histopathology examination and immunohistochemistry for PRRSV, CD79a, CD3 and macrophages in select tissues are planned.