PCV2 Associated Lesions
PCV2 associated disease diagnosis can not be done without evaluation of microscopic lesions. The hallmark lesions in growing pigs are lymphoid depletion and histiocytic replacement of follicles in lymphoid tissues and granulomatous inflammation in a variety of organs such as liver, kidney, lungs, heart and intestines (Sorden, 2000). Chianini et al. (2003) described three stages in pigs with naturally occurring PMWS. Stage I is characterized by mild lymphoid depletion and mild histiocytic infiltration with few multinucleated giant cells mainly in germinal centers of follicular areas of lymphoid tissues. Stage II is characterized by moderate lymphoid depletion of follicles in lymphoid tissues with moderate histiocytic infiltration. Stage III is characterized by loss of follicles in lymphoid tissues and by marked histiocytic replacement of such areas (Chianini et al., 2003). Sarli et al. (2001) described the (1) initial stage: remnants of lymphoid follicles are present, (2) intermediate stage: absence of lymphoid follicles and a more extensive depletion of interfollicular tissue, and (3) end stage: absence of follicles, lymphoid cell depletion and medulla-like tissue prevalence over the lymphoid tissue. In aborted fetuses, the hallmark lesion is necrotizing to necrotizing and lymphohistiocytic myocarditis. Determining if PCV2 associated microscopic lesions are present or not is critical for the diagnosis of PMWS (Sorden, 2000).
Chianini F, Majo N, Segales J, Dominguez J, Domingo M: Immunohistochemical characterization of PCV2 associate lesions in lymphoid and non-lymphoid tissues of pigs with natural postweaning multisystemic wasting syndrome (PMWS). Vet Immunol Immunopathol. 94:63-75, 2003
Sarli G, Mandrioli L, Laurenti M, Sidoli L, Cerati C, Rolla G, Marcato PS: Immunohistochemical characterization of the lymph node reaction in pig post-weaning multisystemic wasting syndrome (PMWS). Vet Immunol Immunopathol. 83:53-67, 2001
Sorden SD: Update on porcine circovirus and postweaning multisystemic wasting syndrome (PMWS). Swine Health Prod. 8:133-136, 2000