Genetic Variations of Thai PRRSV after the 2010 HP-PRRSV Outbreak in Thailand

Abstract

Since multiple HP-PRRSV outbreaks occurred in Thailand in 2010, PRRSV infection was one of major reasons for economic losses in the Thai swine industry. To improve knowledge about the disease and effects of novel PRRSV isolates introduced in Thailand, comparative analysis and genetic characteristics of the hyper-variable regions, NSP2 and ORF5, of PRRSV collected from the clinically-affected herds between February and October 2012 were studied. Partial NSP2 and ORF5 sequences of PRRSV obtained from clinically infected pigs from 11 different herds originated from different geographic regions of Thailand were aligned and used for phylogenetic tree constructions. Eleven sequences were successfully sequenced in this study. Ten sequences collected from 9 provinces in 4 parts of Thailand showed 30 amino acids deletions, closely related to the newly introduced HP-PRRSV while 1 sequence from the central part of Thailand had the similarity to the local Thai type 2 PRRSV. The studied Thai PRRSVs were located separately in these 2 groups in the partial NSP2 and ORF5 based phylogenetic tree. The results indicate that the novel virus were reintroduced in Thailand after the 2010 outbreaks, simultaneously with the local virus evolution. It should be noted that most clinical cases of PRRS during this study were caused by HP-PRRSV infection with a local Thai type 2 PRRSV infection. However, further study is needed to reveal more knowledge on the newly introduced virus in the Thai pig population.