Increasing porcine PARV4 prevalence with pig age in the U.S. pig population.

A novel parvovirus in pigs currently known as porcine PARV4 was recently discovered in pigs in Asia and Europe. The objective of this study was to investigate if porcine PARV4 is present in the U.S. pig population using a newly developed quantitative real-time PCR assay. Lung tissues obtained from 483 pigs across five different age groups with varying disease manifestations (reproductive failure/abortion, enteritis, respiratory disease, systemic/central nervous disease) were tested. While porcine PARV4 DNA was not detected in fetuses (0/28) or suckling pigs (0/15), it was detected in pigs from 10 of 16 states with increasing prevalence rates in the older pigs. Specifically, porcine PARV4 DNA was detected in 5.6% (10/178) of the nursery pigs, 18.7% (44/235) of the grow-finish pigs and 22.2% (6/27) of the mature pigs tested. Genome sequence comparison and phylogenetic analysis of U.S. porcine PARV4s confirmed that they have similar genomic characteristics and 97.6-99.1% sequence identities to available porcine PARV4 sequences from China, Romania, and the U.K. Porcine PARV4 was identified in 14.4% of respiratory cases and in 11.6% of cases with a history of systemic/central nervous system disease. As strict non-diseased controls were not included in this study, a possible role of porcine PARV4 in these disease manifestations remains inconclusive. To the authors' knowledge, this is the first description of porcine PARV4 in the U.S. pig population.