This document discusses the etiology, pathogenesis, and epidemiology of porcine reproductive and respiratory syndrome (PRRS) in the Asia Pacific region. PRRS is caused by the PRRS virus (PRRSV), which is an enveloped, single-stranded RNA virus. There are two major genotypes of PRRSV, type 1 (European) and type 2 (North American), which share about 60% genetic identity. In 2006, a highly virulent strain of PRRSV emerged in China that caused high fever and high mortality in pigs. Known as highly pathogenic PRRS (HP-PRRS), this strain is characterized by a 30 amino acid deletion in its nsp2 region. Since 2007,

1. ETIOLOGY, PATHOGENISIS AND EPIDEMIOLOGY OF PRRS IN
THASIAN PACIFIC REGION
Michihiro Takagi
Virus Disease and Epi demiology Research Division, National Institute of Animal Health,
NARO, Tsukuba, Ibaraki, Japan
ABSTRACT
Porcine reproductive and respiratory syndrome (PRRS) causes reproductive failure in sows and respiratory
disorder in piglets and growing pigs, and is one of the most economically significant swine diseases in pig
production countries. PRRS virus (PRRSV) causing this disease is classified in the order Nidovirales,
family Arteriviridae, genus Arterivirus, and is a small and enveloped virus with a single-stranded
positive-sense RNA genome of approximately 15 kb in length. As for PRRSV, type 1 (European type) and
type 2 (North American type) genotypes are classified by approximately 60% nucleotide identity at
genetically level. The genome of PRRSV contains at least ten open reading frames (ORFs). ORF5 encoding
envelope protein is mainly used for phylogenetic analyses of PRRSV isolates because of its high variability
among viruses of same genotype. In addition, non-structural protein 2 also represents the genetically
variable region of PRRSV genome. In 2006, a disease called “porcine high fever syndrome” emerged in
China. The disease was characterized by high fever of above 41 ˚C, abortion in sows and high mortality in
all age group.Thisdisease caused by an atypical highly virulent strain ofPRRSV, deleted 30 amino acids in
nsp2 region, is called “highly pathogenic PRRS (HP-PRRS)”. HP-PRRS has spread in Southeast Asian
countries since 2007 and it has cause severe damage to the pig production in this region. However, the
virulence and pathogenicity of typical- and HP-PRRSV has not been clarified. In this workshop, the
presentation will discuss the pathogenicity of typical- and HP-PRRSV and currently situation of PRRS in
the Asia Pacific region.