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Title: DIFFERENCE IN SEVERITY OF PORCINE CIRCOVIRUS TYPE 2 (PCV2)-INDUCED PATHOLOGICAL LESIONS AND DISEASE BETWEEN LANDRACE AND PIETRAIN PIGS

Author
item OPRIESSNIG, T - VET. DEPT. ISU AMES, IOWA
item PATTERSON, AR - VET. DEPT. ISU AMES, IOWA
item MADSON, D.M - VET. DEPT. ISU AMES, IOWA
item ROTHSCHILD, M - ANI DEPT. SCI AMES,IOWA
item Kuhar, Daniel
item Lunney, Joan
item JUHAN, N.M - VPISU BLACKSBURG, VA
item MENG, X.J - VPISU BLACKSBURG, VA
item HALBUR, P.G - VPISU BLACKSBURG, VA

Submitted to: Journal of Animal Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 1/30/2009
Publication Date: 5/2/2009
Citation: Opriessnig, T., Patterson, A., Madson, D., Rothschild, M., Kuhar, D.J., Lunney, J.K., Juhan, N., Meng, X., Halbur, P. 2009. Difference in severity of porcine circovirus Type 2 (PCV2)-induced pathological lesions and disease between Landrace and Pietrain pigs. Journal of Animal Science. 87:1582-1590.

Interpretive Summary: Anecdotal information from pig producers and veterinarians in the field suggests that there are genetic differences in susceptibility to porcine circovirus type 2 (PCV2) associated disease (PCVAD) among Landrace and Pietrain breeds. Thus the objective of this study was to determine if a difference exists in PCV2 susceptibility between Landrace and Pietrain pigs under infection controlled, experimental conditions. Genetic studies were planned for 39 Landrace and 39 Pietrain piglets randomly divided into the following control -NEG (n = 13 Landrace; n = 13 Pietrain), and PCV2 infected groups -PCV2 (n = 26 Landrace; n = 26 Pietrain. Maternal antibodies normally protect piglets from PCV2 infection, thus tests were perfomed to confirm that these maternal antibodies, or immunoglobulins (Igs) had waned before the Landrace-PCV2 and Pietrain-PCV2 groups were inoculated with PCV2. The control Landrace-NEG and Pietrain-NEG groups were housed in a separate room, remained non-inoculated, and served as negative controls. All pigs in all groups were necropsied at 21 days post PCV2-inoculation. The PCV2 response phenotype data collected included day of onset and levels of anti-PCV2-IgM, anti-PCV2-IgG, and anti-PCV2 neutralizing antibodies. All Ig levels were similar in Landrace-PCV2 and Pietrain-PCV2 groups. Furthermore, the amount of viral DNA and plasma cytokine levels in serum samples was not different between the two PCV2-inoculated groups. The most striking difference between Landrace and Pietrain pigs was the severity of PCV2-associated microscopic lesions; Landrace-PCV2 pigs had significantly (P < 0.05) more severe lymphoid lesions than the Pietrain-PCV2 pigs. Interestingly, although the pigs originated on the same farm where their dams were co-mingled, passively-acquired anti-PCV2-antibodies waned in Pietrain pigs earlier (by approximately 12 weeks of age) than the majority of the Landrace pigs, who remained PCV2 seropositive until 18 weeks of age and beyond. The results from this study indicate that a genetic difference exists between these two breeds of pigs in susceptibility to PCV2-induced pathological lesions. This data serves as a basis for future genetic studies of loci controlling resistance and to more detailed analyses for biomarkers like cytokines that predict which pigs would resist PCV2 infection more effectively.

Technical Abstract: Anecdotal information from pig producers and veterinarians in the field suggests that there are genetic differences in susceptibility to porcine circovirus type 2 (PCV2) associated disease (PCVAD) among Landrace and Pietrain breeds. The objective of this study was to determine if a difference exists in PCV2 susceptibility between Landrace and Pietrain pigs under experimental conditions. Thirty-nine Landrace piglets and 39 Pietrain piglets were blocked by breed, sire, dam, and litter and randomly divided into the following four groups: Landrace-NEG (n = 13; Landrace), Pietrain-NEG (n = 13; Pietrain), Landrace-PCV2 (n = 26; Landrace), and Pietrain-PCV2 (n = 26; Pietrain). After waning of passively acquired anti-PCV2 antibodies, Landrace-PCV2 and Pietrain-PCV2 groups were inoculated with PCV2 isolate ISU-40895. Landrace-NEG and Pietrain-NEG groups were housed in a separate room, remained non-inoculated, and served as negative controls. All pigs in all groups were necropsied at 21 days post PCV2-inoculation. Onset of seroconversion and levels of anti-PCV2-IgM, anti-PCV2-IgG, and anti-PCV2 neutralizing antibodies were similar in Landrace-PCV2 and Pietrain-PCV2 groups. Furthermore, the amount of PCV2 DNA and cytokine levels in serum samples was not different between the two PCV2-inoculated groups. The most striking difference between Landrace and Pietrain pigs was the severity of PCV2-associated microscopic lesions as Landrace-PCV2 pigs had significantly (P < 0.05) more severe lymphoid lesions than the Pietrain-PCV2 pigs. Interestingly, although the pigs originated on the same farm where their dams were co-mingled, passively-acquired anti-PCV2-antibodies waned in Pietrain pigs by approximately 12 weeks of age whereas the majority of the Landrace pigs remained PCV2 seropositive until 18 weeks of age and beyond. The results from this study indicate that a genetic difference exists between these two breeds of pigs in susceptibility to PCV2-induced pathological lesions.