A Research Blog

Mosquitoes

Dengue and chikungunya are mosquito-borne diseases that are currently re-emerging as public health burdens worldwide. Annually, over 390 million people are infected with dengue, while chikungunya periodically emerges in highly populated areas. The primary vector for the two diseases is Aedes aegypti, a mosquito that thrives in domestic areas.

 Since there is no vaccine for these arboviruses, vector control remains the best way to control the incidence of these diseases. In the 1960s, the Singapore government started a vector control campaign in order to prevent the transmission of dengue by Aedes aegypti. Measures included mosquito and clinical surveillance, public health education, community participation, fines for allowing mosquito breeding, among others. While this campaign drastically reduced the number of households with Aedes mosquitoes and the incidence of dengue in Singapore until the 1990s, dengue epidemics have since increased in frequency, and chikungunya re-emerged in 2008.

 To better understand this paradoxical situation Principal Research Scientist Ian Mendenhall and Assistant Professor Julien Pompon from Duke-NUS Medical School (Duke-NUS) led research that investigated whether peridomestic areas, or areas near inhabited areas, could be the cause or source of these diseases.

 Between 2013 and 2015, the Duke-NUS team surveyed 12 forested sites, which included West Coast Park, three sites in East Coast Park, Sentosa, Pulau Semkau, Kent Ridge Park, Whampoa along the Kallang River, Bukit Timah Nature Reserve, and three open air sites for mosquito vectors. Aedes albopictus and Aedes malayensis were present in these peridomestic sites, but not Aedes aegypti. The team further investigated the susceptibility of these vectors to dengue and chikungunya by infecting them with the viruses. They were found to be highly susceptible to infection by dengue and chikungunya viruses from Singapore. Furthermore, infectious virus particles were detected in their saliva, indicating that they are capable of transmitting dengue and chikungunya viruses.

The Duke-NUS study, recently published in PLOS Neglected Tropical Diseases, shows that Aedes albopictus and Aedes malayensispossess the characteristics that are necessary to contribute to dengue and chikungunya virus transmission in cities. They also suggest that peridomestic areas, such as forested areas and parks, should be assessed for inclusion in vector management programmes.

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