Emergence and pathogenicity of highly pathogenic Porcine reproductive and respiratory syndrome virus in Vientiane, Lao People’s Democratic Republic

Abstract

Highly pathogenic porcine reproductive and respiratory syndrome (HP-PRRS) characterized by high fever, high morbidity, and high mortality in pigs of all ages emerged in China in 2006 and spread rapidly throughout Southeast Asia. In July 2010, a highly contagious swine disease with clinical signs similar to those of HP-PRRS was observed in the Lao People’s Democratic Republic (Lao PDR). A field investigation covering 8 pig farms and 1 slaughterhouse in 7 different districts in the capital city of Vientiane was conducted to identify the disease. Total mortality rates ranged from 6.02% in boars to 91.28% in piglets (mean 54.15%) across the farms investigated. Emergence of the HP-PRRS virus (HP-PRRSV) in Lao PDR was confirmed using real-time reverse transcription polymerase chain reaction as well as virus isolation and identification. An animal inoculation study was performed to characterize the HP-PRRSV responsible for this outbreak. Isolate Laos 1.13 was inoculated into 70-day-old specific pathogen–free pigs to study pathogenicity. Clinical signs of high fever, rubefaction, respiratory distress, nervous symptoms, and diarrhea were observed in inoculated pigs, as well as pathological hemorrhagic lesions consolidated in the lungs. Morbidity and mortality were 100% and 60%, respectively, in inoculated pigs. HP-PRRSV was re-isolated from the inoculated pigs. Results suggested that the newly emerged HP-PRRSV was responsible for recent outbreaks of the swine disease in Lao PDR. The current report highlights the importance of continuous surveillance in neighboring countries to prevent introduction of PRRS to new regions.

Complete Genome Sequence of an Overattenuated Highly Pathogenic Porcine Reproductive and Respiratory Syndrome Virus

“…Highly pathogenic PRRSV (HP-PRRSV) is a mutant of PRRSV containing a novel discontinuous 30-aminoacid (30-aa) deletion in nonstructural protein 2 (Nsp2) (7,12). HP-PRRSV is the etiological agent of HP-PRRS epidemics, which first emerged in southern China in 2006; the virus is currently widespread in China and several Southeast Asian countries, causing enormous economic losses (1,3,6,9,12). Live attenuated PRRSV vaccines based on serial in vitro passage are efficient tools that can be used to protect pigs against PRRSV infection (8,13).…”

Assessment of the Safety and Efficacy of an Attenuated Live Vaccine Based on Highly Pathogenic Porcine Reproductive and Respiratory Syndrome Virus

“…Since then, HP-PRRSV has been the major epidemic viral strain in pigs in China, causing enormous economic losses. Subsequently, HP-PRRSV was detected in countries neighboring China, including Vietnam and Laos (11,12).…”

“…Since then, HP-PRRSV has been the major epidemic viral strain in pigs in China, causing enormous economic losses. Subsequently, HP-PRRSV was detected in countries neighboring China, including Vietnam and Laos (11,12).Two types of commercial vaccines, modified live-attenuated vaccines (MLVs) and inactivated vaccines, are currently available against PRRSV (13,14). Inoculation with vaccines (especially live attenuated vaccines) can provide protection against PRRSV infections and prevent the spread of this disease.…”

Porcine Reproductive and Respiratory Syndrome Virus, Thailand, 2010–2011

“…The disease, referred to as porcine high fever disease (PHFD), was caused by a new PRRSV variant with a unique hallmark: 2 discontinuous 30-aa deletions in Nsp2. The variant, identifi ed as a highly pathogenic (HP) PRRSV, has subsequently become endemic in PRC (7), and it has spread to other countries, including Vietnam (8) and Lao People's Democratic Republic (Lao PDR) (9).…”