Mosquitoes (Diptera: Culicidae) of Singapore: Updated Checklist and New Records.

Prior to 1965, Singapore was part of the Malaya (now Malaysia) and was usually not mentioned when mosquito records were reported for Malaya. Consequently, many species that occurred in Singapore were not listed in the world mosquito catalog, and the available checklist for Singapore since 1986 is incomplete, with some imprecise species information. In updating this checklist, we examined and verified mosquito specimens collected from Singapore in various depositories, including a thorough review of past taxonomic literature. Here, we report a checklist of 182 mosquito species, 33 new distribution records, and a consolidated status list of vectors for Singapore. As Singapore is a travel hub and hosts one of the busiest container ports in the world, there is a risk of introducing mosquito species and their associated pathogens of human disease to the country. Hence, the distribution records are important to increase our knowledge on mosquito ecology as well as to understand the risk of newly introduced vectors and their associated pathogens.

Entomological investigation and control of a chikungunya cluster in Singapore.

In August 2008, a team from the National Environmental Agency conducted an entomological investigation of a chikungunya cluster in Singapore, with the primary aim of identifying the vector responsible for the outbreak and to assess the vector control operation. A total of 173 adult mosquitoes were caught using both the sweep-net method and the BG Sentinel Traps in and around the affected workers' quarters. Of these, 120 (69.4%) were Aedes albopictus and the rest were Culex quinquefasciatus. More than 2700 Ae. albopictus larvae were also collected from 33 breeding habitats detected. No Aedes aegypti was found. During the preintervention period, 6 (8.4%) out of 71 adult female Ae. albopictus were found positive for the chikungunya virus (CHIKV). Vector control measures resulted in a 90% reduction of adult Ae. albopictus caught by BG Sentinel Traps. Postintervention surveillance revealed the presence of CHIKV-positive mosquitoes. These findings led to continued intensive vector control operation in the affected area that further reduced vector population and interrupted the transmission of the disease. The E1 gene sequence of the CHIKV was identical to those of CHIKV isolated from human chikungunya cases working in the affected area, and contained the A226V mutation. The incrimination of Ae. albopictus as a major vector involved in the transmission of A226V CHIKV had led to the revision of chikungunya control strategy in Singapore. This study suggests the benefit of a vector control program that includes the evaluation of control measures in conjunction to virological surveillance in vector population.