Emergence of a virulent porcine reproductive and respiratory syndrome virus in Taiwan in 2018

Summary In March 2018, an abortion storm caused by porcine reproductive and respiratory syndrome virus was confirmed in a farrow‐to‐finish pig herd in Taiwan. Open reading frame 5 and non‐structural protein 2 of the virus confirmed that the virus is closely related to the virulent strains circulating in the United States.

report of deletion/insertion pattern analysis for the NSP2 gene of PRRSV (Deng et al., 2015). We report the emergence of a virulent PRRSV isolate in a PRRSV-vaccinated herd in Taiwan, designated PRRSV/TW/ NPUST-107-844/2018(NPUST-107-844/2018, that had identical deletion patterns to that in virulent PRRSV isolated in the US.

| Sample collection and history
In March 2018, a 300-sow farrow-to-finish herd with a one-year PRRSV (Ingelvac PRRSV MLV, Boehringer Ingelheim, St. Joseph, MO) vaccination history (mass vaccinated four times per year) that suffered by an abortion storm (30 abortions within 1 month) was observed in southern Taiwan. The farm had introduced a boar from a domestic breeding herd without quarantine one month prior. Aborted fetuses and whole blood from the corresponding sows were submitted to the Animal Disease Diagnostic Center, National Pingtung University of Science and Technology, Taiwan.

| Detection of porcine reproductive and respiratory syndrome virus
Two serum samples from diseased sows and two aborted fetuses from the other diseased sow, including lung, heart, spleen, placenta, and umbilical cord, were mixed and extracted nucleic acid by MagNA Pure LC 2.0 with the MagNA Pure LC Total Nucleic Acid Kit (Roche Applied Science, Indianapolis, IN). Following cDNA synthesis was using PrimeScript™ RT reagent kits (Takara, Kyoto, Japan). All samples were examined by real-time polymerase chain reaction (Lin, Lin, Hung, Wang, & Chiou, 2013).

| Gene amplification and sequencing
The complete open reading frame 5 (ORF5) genes and partial

| Sequencing alignment and phylogenic analysis
Sequences of ORF5 gene and NSP2 amino acid were aligned using Clustal W method and Muscle method in Molecular Evolutionary Genetics Analysis Version 6.0 (MEGA6) software, respectively (Tamura, Stecher, Peterson, Filipski, & Kumar, 2013). The sequence homology of nucleotide and amino acid were determined by the MegAlign software (Lasergene, DNASTAR, Madison, WI). Phylogenetic tree was constructed from the aligned nucleotide sequences using the Maximum Likelihood method and the Kimura 2-parameter model by MEGA6 software (Kimura, 1980). The percent frequencies of the groupings were determined after 1,000 bootstrap evaluation.

| RE SULTS
All samples were PRRSV RNA-positive, and viral loads in the two serum samples were 1.14 × 10 5 (PRRSV/TW/107-844/2018) and In conclusion, this is the first case report of a novel virulent PRRSV in a Taiwanese pig herd, which shares a common evolutionary origin in NSP2 with other virulent PRRSVs in the US, Korea and China. When and how this virus was introduced into Taiwan remains unknown. However, we propose that this virulent strain was introduced into Taiwan in recent years by importing boars and sows from abroad. Further surveillance is worthwhile to define the distribution of this virulent strain of PRRSV among the Taiwanese pig population. These results will also provide the valuable information about the biosecurity concerns (breeding pigs from domestic pig farms as well as from abroad) for the control of PRRSV infection.

| Nucleotide sequence accession numbers
The PRRSV sequences obtained in this study have been deposited in GenBank under accession numbers MK291407-MK291414.

AVA I L A B I LIT Y O F DATA A N D M ATE R I A L S
The data set supporting the conclusions of this article is available in the GenBank.

ACK N OWLED G EM ENTS
We acknowledge and appreciate the excellent technical help provided by Miss Ying-Xiu Lien.

CO N FLI C T O F I NTE R E S T
The authors declared that they have no competing interests.