\n<\/p>\n
Despite the rise, experts said the situation does not pose a major public health risk.<\/p>\n
The Communicable Diseases Agency (CDA) said the risk of Japanese encephalitis virus and West Nile virus \u2013 both transmitted by Culex mosquitoes \u2013 is currently low in Singapore. Culex mosquitoes do not spread dengue.<\/p>\n
CDA’s Group Director of Communicable Diseases Programmes, Associate Professor Lim Poh Lian, said no cases of West Nile virus have been reported in Singapore, while the last local case of Japanese encephalitis was in 2008 and the last imported case in 2015.<\/p>\n
“For these diseases to take root in Singapore, there needs to be sustained presence of these viruses in Culex mosquitoes and animal reservoir hosts such as birds and pigs, as well as human exposure to infected vectors,” Assoc Prof Lim said.<\/p>\n
Duke-NUS Medical School Emeritus <\/span>Professor Duane Gubler said Culex mosquitoes are primarily a nuisance rather than a disease-transmitting pest, and noted that Japanese encephalitis is a rural disease rarely found in urban areas.<\/p>\n “The major amplification host for Japanese encephalitis is pigs, and you don’t grow many pigs in Singapore anymore,” the chair of the Global Dengue and Aedes-Transmitted Diseases Consortium<\/span> said, referring to the country\u2019s past pig farming industry.<\/p>\n Pest experts said Aedes and Culex mosquitoes prefer different breeding habitats, though some overlap exists.<\/p>\n “Unlike Aedes, which is closely associated with cleaner container habitats, Culex is more strongly linked to organically polluted stagnant water, especially blocked drains, dirty gullies, sumps, inspection chambers and similar outdoor water-holding structures,” said Origin Exterminators’ operation manager Lawrence Ng.<\/p>\n Problems with Culex mosquitoes are usually more pronounced in older urban pockets, back lanes, service areas and construction perimeters, he added.<\/p>\n Asked whether suppressing Aedes mosquitoes could have contributed to the rise in Culex populations, NEA said the two species have different breeding habitats and the suppression of Aedes aegypti does not drive Culex increases.<\/p>\n Prof Gubler agreed, saying the two species are ecologically distinct and do not significantly compete.\u00a0<\/p>\n “Singapore is a highly dense population, so there’s always people around, so there would be no competition at all for the blood meals that are needed to produce the eggs. The competition, if it occurred, would have been in the larval habitats, competing for that food,” he added.<\/p>\n Given the higher disease risk from Aedes mosquitoes, experts said control efforts should prioritise them over Culex.\u00a0<\/p>\n<\/div>\nDIFFERENT PESTS, DIFFERENT STRATEGIES<\/h2>\n