Entomological Investigation and Control of a Chikungunya Cluster in Singapore

Abstract

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.

Individual and contextual risk factors for chikungunya virus infection: the SEROCHIK cross-sectional population-based study

“…This neighbourhood effect on CHIKV transmission dynamic was reported in three clusters investigated during the first epidemic wave in Reunion island [ 35 ], and is supported by mapping of participant's residencies revealing spatial heterogeneity of risk (data not shown). This influence of neighbourhood was later confirmed in Singapore [ 36 ]. It is also in agreement with more recent findings from a CHIKF outbreak in a small rural area of Bangladesh [ 37 ].…”

Modeling Dynamic Introduction of Chikungunya Virus in the United States

“…The reported minimum extrinsic incubation period for CHIKV in several studies is 2 days [15]. Hence, we modeled EIP as a linear function with a minimum duration of 1.5 days at 32°C and a maximum duration of 4 days at 10°C [15], [51]. For the purposes of the current model we assumed transmission rates based on early experimental work [52].…”

Entomological Investigation of Aedes aegypti In Neighborhoods With Confirmed Human Arbovirus Infection In Puerto Rico

“…In absence of natural immunity in human populations, the introduction of these viruses resulted in outbreaks of chikungunya (CHIK) and Zika (ZIK) in 2014, respectively (Adams et al 2016. Both of these arboviruses are transmitted between humans by the bite of Aedes species in urban areas (Tan et al 2011). In December 2013 the 1st autochthonous case of CHIK was reported on the Caribbean island of Saint Martin (Fischer and Staples 2014).…”