Sequence analysis of old and new strains of porcine circovirus associated with congenital tremors in pigs and their comparison with strains involved with postweaning multisystemic wasting syndrome.

The entire genomes of 7 isolates of porcine circovirus (PCV) from pigs with congenital tremors (CT), type A2, or postweaning multisystemic wasting syndrome (PMWS) were cloned and sequenced. One isolate (CT-PCV-P7) originated from the late 1960s from a neonatal pig with CT, type A2. Two recent PCV isolates (CT-PCV-P5, CT-PCV-P6) were from 2 affected neonatal pigs, from different farms, with unrelated outbreaks of CT; type A2. Four isolates (PMWS-PCV-P1, PMWS-PCV-P2, PMWS-PCV-P3, PMWS-PCV-P4) originated from pigs with PMWS from 4 different farms. A comparative analysis of these PMWS and PCV isolates demonstrated 99% sequence identity with each other, and over 96% sequence identity with previously sequenced PCV2 isolates. The CT-PCV-P5 and CT-PCV-P6 isolates, however, shared 99% of the same identity with each other, and interestingly also with PMWS PCV isolates. There were no consistent genomic differences between PMWS and recent CT isolates. The CT-PCV-P7 showed 98% identity similarity to PK-15-derived PCV1 and demonstrated only 72% identity similarity to either CT-PCV-P5 or CT-PCV-P6. Phylogenetic analysis confirmed that the old isolate (CT-PCV-P7), and the new isolates (CT-PCV-P5, CT-PCV-P6, PMWS-PCV-P1, PMWS-PCV-P2, PMWS-PCV-P3, PMWS-PCV-P4) were correctly classified as PCV1 and PCV2, respectively.