Evolutionary, epidemiological, demographical, and geographical dissection of porcine bocavirus in China and America

Porcine bocavirus was first discovered in Swedish pigs with post-weaning multisystemic wasting syndrome (PMWS) in 2009. Many efforts have been implemented to investigate the porcine bocavirus, but it remains enigmatic. In the current study, we utilized data from both China and the USA. The China-derived data included 403 pig samples collected from five provinces, 122 gene sequences from the GenBank database, and 637 old porcine bocavirus (PBoV) cases. The USA-derived data comprised 181 pig samples from 18 states, 39 new gene sequences, and 85 new emerging cases. First, we executed a comprehensive analysis of the disease's prevalence, phylogenetics, evolutionary distances, mutation network, geographical distribution, occurrence frequency, and phylogeographical estimation in both China and the USA. The results showed that the positive rates of PBoV (42.0%, 76/181) in American samples were significantly higher than those (11.4%, 46/403) in the Chinese samples. All PBoV cases from these countries can be divided into six groups: PBoV1 (group 1), PBoV2 (group 2), PBoV3C (group 3), PBoV5 (group 4), PBoV3/4 (group 5), and PBoV6V7V (group 6). PBoV1 and PBoV2 were epidemic strains from 2006 to 2011 in China, whereas the PBoV3 subtypes were epidemic from 2010 to 2012 in China and the USA. At present, PBoV3C (group 3), PBoV5 (group 4), and PBoV3/4 (group 5) are epidemic viruses and co-exist in China and the USA. The geographical distribution of PBoV mainly lies in the east and south coastal areas of China and the central states of the USA. Jiangsu Province and the state of Minnesota were the centers of high occurrence frequency of PBoV with six outbreaks. The old PBoV cases involved 14 provinces and regions of China and North Carolina in the USA, whereas the new emerging cases involved five provinces in China and 13 states in the USA, of which two provinces and 12 states reported for the first time that piglets were infected by PBoV. Hong Kong, Hebei, and Jiangsu Provinces and the states of Minnesota and North Carolina were possibly geographical origins of PBoV in China and America, respectively. These data can help us systematically understand porcine bocavirus in China and America and find effective strategies for its treatment.