European and American Strains of Porcine Parainfluenza Virus 1 (PPIV-1) Belong to Two Distinct Genetic Lineages.

Porcine parainfluenza virus 1 (PPIV-1) is a recently emerged respirovirus closely related to human parainfluenza virus 1 (HPIV-1) and Sendai virus (SenV). PPIV-1 has been detected in Asia, the Americas and Europe, but knowledge on its epidemiology and genetic diversity is very limited. In the present study, the complete nucleotide sequences of the fusion (F)-protein gene obtained from samples from 12 Polish and 11 US herds were analysed and compared to previously available genetic data from the Americas, Asia and Europe. The existence of two distinct clades was observed, grouping European sequences and one Hong Kong sequence (clade 1), or one American sequence and three Asian sequences (clade 2). The mean genetic distances measured with the p-distance were 0.04 (S.E., 0.000) within both clades, and 0.095 (S.E., 0.006) between the clades. Moreover, two distinct clusters of highly similar sequences were identified, which corresponded to the geographically distant nurseries and finishing units, from three pig flows within one Polish pig-production company. The obtained data indicate that the two PPIV-1 lineages may have evolved independently in Europe and America. More studies, particularly involving Asian viruses, are necessary to understand the virus' emergence and epidemiology and the role of carriers in the spread of PPIV-1.