Detection of Japanese Encephalitis Virus in Culex Mosquitoes in Singapore

Abstract

. Mosquito-borne flaviviruses are emerging pathogens of an increasing global public health concern because of their rapid increase in geographical range and the impact of climate change. Japanese encephalitis virus (JEV) and West Nile virus (WNV) are of concern because of the risk of reemergence and introduction by migratory birds. In Singapore, human WNV infection has never been reported and human JEV infection is rare. Four sentinel vector surveillance sites were established in Singapore to understand the potential risk posed by these viruses. Surveillance was carried out from August 2011 to December 2012 at Pulau Ubin, from March 2011 to March 2013 at an Avian Sanctuary (AS), from December 2010 from October 2012 at Murai Farmway, and from December 2010 to December 2013 at a nature reserve. The present study revealed active JEV transmission in Singapore through the detection of JEV genotype II in Culex tritaeniorhynchus collected from an Avian Sanctuary. Culex flavivirus (CxFV), similar to the Quang Binh virus isolated from Cx. tritaeniorhynchus in Vietnam and CxFV-LSFlaviV-A20-09 virus isolated in China, was also detected in Culex spp. ( vishnui subgroup) . No WNV was detected. This study demonstrates the important role that surveillance plays in public health and strongly suggests the circulation of JEV among wildlife in Singapore, despite the absence of reported human cases. A One Health approach involving surveillance, the collaboration between public health and wildlife managers, and control of mosquito populations remains the key measures in risk mitigation of JEV transmission in the enzootic cycle between birds and mosquitoes.

Japanese encephalitis in Bali, Indonesia: ecological and socio-cultural perspectives

“…It is even more effective, when it combines with other related control strategies. Controlling the vector population integrated with public health, livestock and wild life managements is an important multisectoral measure for JEV control and prevention program in order to reduce the risk [ 89 ].…”

Mosquito Vector Competence for Japanese Encephalitis Virus

“…It was first isolated from this mosquito species in the 1930s in Japan [ 173 ] as well as later through several decades of Japanese surveillance [ 130 , 136 , 145 ]. Virus isolation was also successful with mosquitoes from Indonesia [ 57 , 132 , 133 , 165 ], India [ 53 , 58 , 70 , 102 , 129 , 137 , 143 ], Malaysia [ 59 , 72 , 74 ], Thailand [ 71 , 135 ], Taiwan [ 28 , 56 , 131 , 134 ], South Korea [ 139 ], Vietnam [ 75 , 141 ], China [ 40 , 41 , 89 , 138 , 140 , 142 , 147 ], Cambodia [ 146 ] and Singapore [ 144 ]. In addition, JEV was detected over the last few decades in Cx .…”

The feasibility of field collected pig oronasal secretions as specimens for the virologic surveillance of Japanese encephalitis virus

“…Thus oronasal secretions may be useful for routine JEV surveillance, especially for the epidemic area, such as Hokkaido, Japan, where it has been very challenge to identify circulating virus-positive mosquitoes [ 22 ]. However, mosquito surveillance is still critical in some area, such as Singapore, where pig farming has not been widely practiced [ 20 ].…”

“…Phylogenetic analysis of the viruses demonstrates the replacement of genotype III (GIII) virus by genotype I (GI) virus, and illustrates geographical expansion of the emerging GI viruses in the epidemic regions of Asia [ 17 , 18 ]. However, GII, GIII, and GIV viruses remain circulating in Singapore, Philippine, and Indonesia, respectively [ 19 , 20 ]. Emerging GI virus has been showed it is capable of enhancing replication in experimentally infected pigs and is less susceptible to the current GIII vaccine-induced antibodies [ 21 ].…”