Study on the resting preferences of Aedes aegypti (Linnaeus) and Ae. albopictus (Skuse) adult mosquitoes in the district of Colombo

Abstract

Aedes aegypti (Linnaeus) and Aedes albopictus (Skuse) are the world’s most widely distributed mosquito species and, act as major contributors to many mosquito-borne diseases. Remarkable behavioral and ecological attributes make these mosquitoes as efficient vectors. Due to the behavioral and ecological plasticity of Ae. aegypti and Ae. Albopictus, it has become a major limitation in vector control and disease management measures in Sri Lanka. The objective of this study was to determine key bionomics aspects, namely resting preferences of Ae. aegypti and Ae. albopictus in the District of Colombo. Three Medical Officer of Health (MOH) areas were selected for the current study based on previous dengue cases. The two high risk areas (Maharagama and Kolonnawa) and a low-risk area (Padukka) were selected as study sites. Adult mosquito surveillance was conducted in outdoor and indoor settings using a mouth aspirator for one year (November, 2019-October, 2020). Adult mosquito collection included the aspiration from all rooms within the home including furniture, behind hanging clothes and curtains, behind and around cooking utensils and from dark and humid places, where mosquitoes were found resting. A total of 658 Aedes adult mosquitoes were collected from both indoor and outdoor resting locations (total number of resting sites= 432). The most abundant vector species was Ae. aegypti (65.0%; n=428), followed by Ae. albopictus (35.0%; n= 230) in Maharagama and Kolonnawa MOH areas. The most and least abundant Aedes mosquito collection MOH areas were Maharagama 44.5% (n=293) and Padukka 23.2% (n=153), respectively. Ae. Aegypti adult mosquitoes denoted an endophilic behaviors (97.1%; n=416), while Ae. albopictus denoted an exophilic resting behavior (81.30% n= 187). In terms of resting places, Ae. aegypti was mostly found in resting places such as bedroom (36.0%; n=154), kitchen (26.2%; n=112) living room (21.3%; n=91), and outdoor vegetation (1.4%; n=06). Meanwhile, Ae. albopictus was conducive to rest on the vegetation (50.4%; n=116), front of the house-external (23.8%; n=109). The highest percentage of Aedes mosquitoes were found resting on wooden surfaces in both indoor and outdoor sites (52.3%; n=344), followed by clothes/curtains (24.2%; n=159) and cement surfaces (17.0%). Resting behavior of vectors is an important fact since they are prerequisites to determine their role in disease transmission in endemic settings. This study revealed that the resting behavior varied between the two Aedes vector species, were Ae. aegypti adult mosquitoes denoted highly endophilic nature, while Ae. albopictus demonstrated exophilic behavior. In this study Ae. aegypti was mainly found resting in bedrooms, living rooms and kitchens and Ae. albopictus was found resting mainly among outdoor vegetation. The outcome of this study facilitates the relevant health authorities who engage with dengue control programs, to successfully eradicate the vector from resting sites.