Host genetics seems to play a major role on the development of the virus systemic disease. Landrace pigs, for example, develop more severe lymphoid lesions and clinical disease than Duroc, Large White and Pietrain pigs. Hampshire boars, on the other side, have less clinical signs occurrence of the disease. To sum up, there's a clear link between genetics and clinical expression. Anyway, there's no knowledge on the mechanisms that may cause this.
Porcine circovirus 2 is genetically stable and has a long-lasting infection in the individual host. Usually pigs are infected by several genetically related strains for the same genotype. It's posible too to have a co-infection. It's suspected that this virus presents a quasi-species structure. This means that the virus can show different mutations in a same animal. To confirm that point it would be necessary to do extensive sequencing analyses in different individuals.
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