Abstract:
A survey on mosquito species was conducted once a month in a PRRS positive farm in Nakorn Pathom province during May 2004 to April 2005. The mosquito larvae were collected in the vicinity of 1 km and the adult females were captured while feeding on the pigs by using oral aspirators between 6 to 10 pm. Of 91,840 mosquitoes, there were 3 genus and 6 species as the following Culex tritaeniorhynchus, Cx. Gelidus, Mansonia uniformis, Ma. Annulifera, Anopheles vagus and An. Peditaeniatus with the predominant of Cx. Tritaeniorhynchus (60-95.75%) and Ma. annulifera was the least (0.02-0.05%). Collected mosquitoes larvae include Cx. Tritaeniorhynchus, Cx. gelidus, An. vagus and An. peditaeniatus. To determine whether Cx. Tritaeniorhynchus could serve as a potential vector for PRRSV transmission, 2 experiments were conducted: the duration of PRRSV within the mosquitoes and the PRRSV transmission from the PRRSV-infected pigs to the naive pigs by infected mosquitoes. PRRSV could be detected in mosquito pooled samples for up to 48 hours post feeding on the PRRSV-infected pig (PFP) using RT-PCR, whereas the PRRSV could be isolated from the mosquito samples for up to 2 hours PFP. The results of PRRSV transmission showed that all naive pigs used in the mosquito contact protocol were negative, whereas, the swine bioassay using pooled mosquitoes 30 minutes PFP was positive for PRRSV detection by both RT-PCR and ELISA. The results of this study demonstrated that Cx. tritaeniorhychus, a predominant mosquito species found in a pig farm which was able to transmit PRRSV mechanically and was unlikely to transmit the PRRSV via biting or sucking blood.