Coronaviruses are known to infect humans and other animals and cause respiratory and gastrointestinal diseases.

In a paper published in the online journal, mBio, Yao-Wei Huang of Virginia Polytechnic Institute and State University and co-authors there and at other institutes in the US and China report the emergence of PED virus (PEDV) in the United States and determination of its origin, evolution and genotypes based on temporal and geographical evidence.

Histological lesions in small intestine sections of affected pigs and the complete genomic sequences of three emergent strains of PEDV isolated from outbreaks in Minnesota and Iowa were characterised.

Genetic and phylogenetic analyses of the three US strains revealed a close relationship with Chinese PEDV strains and their likely Chinese origin. The US PEDV strains underwent evolutionary divergence, which can be classified into two sub-lineages. The three emergent US strains are most closely related to a strain isolated in 2012 from Anhui Province in China, which might be the result of multiple recombination events between different genetic lineages or sub-lineages of PEDV.

Molecular clock analysis of the divergent time based on the complete genomic sequences is consistent with the actual time difference, approximately two to three years, of the PED outbreaks between China (December 2010) and the United States (May 2013).

The finding that the emergent US PEDV strains share unique genetic features at the 5′-untranslated region with a bat coronavirus provided further support of the evolutionary origin of PEDV from bats and potential cross-species transmission.

The data from this study have important implications for understanding the ongoing PEDV outbreaks in the United States and will guide future efforts to develop effective preventive and control measures against PEDV, concluded Huang and co-authors.

Outlining the importance of their result, they continue that the sudden emergence of PEDV, a coronavirus, for the first time in the United States causes significant economic and public health concerns.

Since its recognition in May 2013, PEDV has rapidly spread across the United States, resulting in high mortality in piglets in more than 17 States now.

The ongoing outbreaks of Middle East respiratory syndrome coronavirus in humans from countries in or near the Arabian Peninsula and the historical deadly nature of the 2002 outbreaks of severe acute respiratory syndrome coronavirus create further anxiety over the emergence of PEDV in the United States due to the lack of scientific information about the origin and evolution of this emerging coronavirus.

The researchers' report on the detailed genetic characterization, origin and evolution of emergent PEDV strains in the United States provides much needed information to devise effective preventive and control strategies against PEDV in the United States, Huang and co-authors added.

Reference

^{Huang Y-W., A.W. Dickerman, P. Piñeyro, L. Li, L. Fang, R. Kiehne, T. Opriessnig and X-J. Meng. 2013. Origin, evolution, and genotyping of emergent porcine epidemic diarrhea virus strains in the United States. mBio 4(5):e00737-13. doi: 10.1128/mBio.00737-13}

October 2013