Vector competence of Culex tritaeniorhynchus and Culex quinquefasciatus (Diptera: Culicidae) for duck Tembusu virus transmission.

Duck Tembusu virus (DTMUV), an emerging infectious disease in ducks, was detected in Culex (Cx.) tritaeniorhynchus mosquitoes collected from a duck farm; however, the exact role of mosquitoes in the ecology of DTMUV in Thailand remains unclear. Vector competence of Cx. tritaeniorhynchus and Cx. quinquefasciatus was examined for DTMUV. Cx. tritaeniorhynchus mosquitoes were allowed to feed on four levels (102, 103, 104, and 105 TCID50/mL) of DTMUV, while Cx. quinquefasciatus were allowed to feed on two levels (104 and 105 TCID50/mL) of DTMUV. Infection rates in Cx. tritaeniorhynchus were 1.6, 10.2, 35.8, and 59.3% after feeding on 102, 103, 104, and 105 TCID50/mL of DTMUV, respectively, while dissemination and transmission were 20.3 and 16.9% after feeding on 105 TCID50/mL of DTMUV. Infection rates in Cx. quinquefasciatus were 2.5 and 2.3% after feeding on 104 and 105 TCID50/mL of DTMUV, respectively, with no virus dissemination and transmission found in all tested mosquitoes. Another study was conducted to examine the transovarial transmission of DTMUV in Cx. tritaeniorhynchus. Mosquitoes were allowed to feed on blood meal infected with 105 TCID50/mL of DTMUV. Each blood-fed mosquito was isolated and allowed to lay eggs. After oviparity, the mosquitoes were tested for DTMUV infection; 43 DTMUV infected and 37 non-infected female mosquitoes with eggs were included. A total of 182 F1 progeny from DTMUV infected mosquitoes and 145 F1 progeny from non-infected mosquitoes were tested for DTMUV but all were negative. Findings indicated the potential role of Cx. tritaeniorhynchus in the DTMUV transmission cycle in duck farms in Thailand. No transovarial transmission of DTMUV was found in Cx. tritaeniorhynchus.

Duck Tembusu virus detection and characterization from mosquitoes in duck farms, Thailand.

Duck Tembusu virus (DTMUV), an emerging infectious disease in ducks, belongs to the Flavivirus genus and Flaviviridae family. The transmission of DTUMV involves mosquito vectors; however, the exact role of mosquitoes in the ecology of DTMUV in Thailand remains unclear. This study was conducted to examine DTMUV detection and characterization from mosquitoes in duck farms in central Thailand. Mosquitoes were collected from two duck farms in Sing Buri Province and two duck farms in Ang Thong Province from September 2015 to July 2016 using four CDC-light traps. A total of 30,841 mosquitoes were collected and identified to seven species (Anopheles (An.) barbirostris, An. stephensi, Culex (Cx.) gelidus, Cx. quinquefasciatus, Cx. tritaeniorhynchus, Mansonia (Ma.) annulifera and Ma. uniformis). The most common collected species from each duck farm and each collection time was Cx. tritaeniorhynchus. Mosquitoes were pooled according to species, location, and collection time and then examined for DTMUV by RT-PCR. A total of 273 mosquito pools were examined, with only one pool of Cx. tritaeniorhynchus collected from Sing Buri Province in November 2015 testing positive for DTMUV. Phylogenetic analysis of the polyprotein genes demonstrated that a mosquito-derived Thai DTMUV was grouped into subcluster 2.1 and most closely related to the 2013 Thai DTMUVs. Thus, this study indicated that Cx. tritaeniorhynchus may play a role as a vector in the transmission of DTMUV in Thailand. However, additional studies concerning the vector competence of this mosquito for DTMUV are needed.