Potential vectors of PRRSV in mosquitoes genus Culex from a PRRSV-positive swine farm in Nakhon Pathom Province

Abstract

The aims of this study were to survey the prevalence of mosquito species observed in a pig farm and to determine whether they could serve as a potential vectors in the role of PRRSV transmission among pigs. Mosquito survey was conducted during March to August, 2004. At least, 3 genus, 4 species, Culex tritaeniorhynchus, Culex gelidus, Anopheles spp. and Mansonia uniformis were identified in the farm. Of which C. tritaeniorhynchus was predominant (85.68%). Others were found at 12.13%, 2.06% and 0.13%, respectively. To determine whether C. tritaeniorhynchus could serve as a potential vector of PRRSV transmission, 2 experiments were conducted: the duration of PRRSV within mosquitoes and the assessment to transmit PRRSV from PRRSV-infected pig to naive pigs by mosquitoes. By RT-PCR detection from the C. tritaeniorhynchus samples, the PRRSV was detected up to 48 hours post feeding on a PRRSV-infected pig. The virus was also isolated from C. tritaeniorhynchus and the live PRRS virus could be isolated from mosquito samples up to 2 hours post feeding on an infected pig. To assess whether C. tritaeniorhynchus could transmit PRRSV from PRRSV-infected pig to the naive pigs, the direct mosquitoes to pig protocol and the swine bioassay were developed. The results showed that all naive pigs used in the direct mosquitoes to pig protocol were negative, whereas, the swine bioassay using the mosquitoes which fed 30 minutes on the infected pig was positive for PRRSV detection. The results of this study indicated that C. tritaeniorhynchus, a predominant mosquito species found in a pig farm, was able to transmit PRRSV mechanically and is likely to serve as a potential role of PRRSV transmission in the pig farm. These results are useful for the prevention and control of PRRSV transmission in the pig farms and for a better understanding of PRRS epidemiology.