The emergence and spread of Type 2 Porcine Reproductive and Respiratory Syndrome virus (Type 2 PRRSV) in North America is heavily influenced by the multiple site production system used in the hog industry. However, it is unclear how anthropogenic factors such has this have shaped the current spatial distribution of PRRSV genotypes. We employed Bayesian phylogeographic analyses of 7040 ORF5 sequences to reveal the recent geographical spread of Type 2 PRRSV in North America. The directions and intensities in our inferred virus traffic network closely mirror the hog transportation. Most notably, we reveal multiple viral introductions from Canada into the United States causing a major shift in virus genetic composition in the Midwest USA that went unnoticed by the regular surveillance and field epidemiological studies. Overall, these findings provide important insights into the dynamics of Type 2 PRRSV evolution and spread that will facilitate programs for control and prevention.
Bibliographical noteFunding Information:
This work was supported by grants from the Research Grant Council of the Hong Kong Government ( GRF770612 ) and HKU Strategic Research Theme of Infection and Immunology to FCL and from the European Community's Seventh Framework Programme (FP7/2007-2013) under Grant Agreement no. 278433 and ERC (Grant agreement no. 260864 ) to PL. MS is supported by an International Postgraduate Research Scholarship from the University of Sydney, while ECH is supported by an NHMRC Australia Fellowship. Special thanks are given to Kay Faaberg, National Animal Disease Center, Ames, IA, and Trevor Wennblom, University of Minnesota, Minneapolis, MN, for database maintenance.
- Molecular epidemiology