Culex tritaeniorhynchus is Unlikely to be a Vector for the Porcine Reproductive and Respiratory Syndrome Virus (PRRSV)

Abstract

At least, 4 mosquito species, Culex tritaeniorhynchus, Culex gelidus, Anopheles vagus and Mansonia uniformis were identified on a pig farm in Nakorn Pathom, Thailand between March 2004 to February 2005. C. tritaeniorhynchus was found to be the predominant species (88.387.63%). To determine whether C. tritaeniorhynchus could serve as a mechanical vector for PRRSV transmission, 2 experiments were conducted on: the duration of PRRSV within the mosquitoes and PRRSV transmission from the PRRSV-infected pigs to native pigs by the infected mosquitoes. PRRSV nucleic acid could be detected in the whole pooled mosquito samples for up to 48 hours post feeding in the PRRSV-infected pig (PFP) using RT-PCR, whereas the PRRSV could be isolated from the whole pooled mosquito samples for up to 2 hours PFP. However, no PRRSV was detected in the pooled mosquito legs. The results of the PRRSV transmission showed that all the native pigs used in the direct mosquito feeding were negative, whereas, the swine bioassay using pooled mosquito injection at 30 minutes PFP was positive for PRRSV detection in both RT-PCR and ELISA tests. The results of this study demonstrate that C. tritaeniorhychus, a predominant mosquito species found on a pig farm in Thailand is unlikely to serve as a potential vector for PRRSV transmission on pig farms.