PCV2 induced alteration of peripheral blood cells
Segalés et al. (2000) studied hematological parameters of 50 pigs with naturally acquired PMWS, 8 experimentally-PCV2-infected pigs, and 11 PCV2-free control pigs. PMWS-affected pigs had significantly lower red blood cells counts and hematocrit values which was associated with the presence of gastric ulcerations rather than with PCV2-infection. The mean lymphocyte percentages were lower in PMWS-affected pigs; however, this was not statistically significant (Segalés et al., 2000). Segalés et al. (2001a) analyzed changes in peripheral blood leukocyte populations in pigs with PMWS by comparing data obtained from 13 PMWS-affected pigs with 11 clinically healthy pigs. It was found that pigs suffering from PMWS had lower proportions of CD4+ and IgM+ cells in blood than clinically healthy pigs (Segalés et al., 2001). Darwich et al. (2002) used twenty-four 8- to 12-week-old PMWS affected pigs and 17 healthy control pigs from conventional farms in Spain to determine changes in peripheral blood monocytes. The authors found that PMWS-affected pigs had significantly (P < 0.05) decreased numbers of CD8+ and double-positive cells compared to control pigs. The amount of PCV2 in lymphoid tissues was correlated to the degree of cell depletion and to the relative decrease in IgM+ and CD8+ cells in peripheral blood (Darwich et al., 2002). Nielsen et al. (2003) found primarily lymphopenia in experimentally PCV2-inoculated pigs. All T lymphocyte subpopulations were susceptible to PCV2 induced lymphopenia with the conclusion that memory/activated Th-lymphocytes might be affected more than other T cell subpopulations. Only pigs that subsequently developed PMWS had lymphopenia (Nielsen et al., 2003). Bassaganya-Riera et al. (2003) demonstrated significant B-cell depletion in PCV2-infected pigs and found that the most depleted B-cell subset (IgM+) expressed an immature phenotype characterized by expression of a myeloid marker (SWC3). Segalés et al. (2004) determined the serum concentrations of acute phase proteins, haptoglobulin, and pig-major acute phase protein, in pigs with and without PMWS and found that mean haptoglobulin and pig-major acute phase protein levels were significantly increased in PMWS-affected pigs. In a second study, pigs were divided into 2 groups based on PCV2-PCR status done on serum samples and no significant differences between groups were detected. The authors concluded that acute phase proteins levels are significantly increased in pigs that develop PMWS but not in pigs with subclinial PCV2 infection (Segalés et al., 2004).
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Segalés J, Pastor J, Cuenca R, Domingo M: Haematological parameters in postweaning multisystemic wasting syndrome-affected pigs. Vet Rec. 146:675-676, 2000
Segalés J, Piňeiro C, Lampreave F, Nofrarías M, Mateu E, Calsamiglia M, Andrés M, Morales J, Piňeiro M, Domingo M: Haptoglobin and pig-major acute protein are increased in pigs with postweaning multisystemic wasting syndrome (PMWS). Vet Res. 35:275-282, 2004