Bionomic aspects of dengue vectors Aedes aegypti and Aedes albopictus at domestic settings in urban, suburban and rural areas in Gampaha District, Western Province of Sri Lanka
Authors: Dalpadado Rasika , Amarasinghe Deepika , Gunathilaka Nayana , Ariyarathna Nalin 
Published: April 2022

Background

The lack of information on behavioural patterns ofAedes aegyptiandAedes albopictushas become a significant limitation in vector control and disease management programmes. Therefore, the current study was focused on determining some bionomics aspects: breeding, resting, host-seeking and feeding preferences ofAe. aegyptiandAe. albopictusin Sri Lanka.

Methods

Larval and adult surveys were conducted from April 2017 to April 2019 monthly in six selected Medical Officer of Health (MOH) areas in Gampaha Distinct, Western province, Sri Lanka, representing urban, suburban and rural settings. Resting preferences of adult mosquitoes were observed from indoor and outdoor places using a Prockopack aspirator. The information on resting height, surface, material and locality was recorded. Human-baited double-net traps were used to determine the host-seeking time ofAedesmosquitoes. Statistical differences in the spatial distribution of mosquitoes in selected MOH areas and prevalence of vectors were analysed using general linear model (GLM). A chi-square test was used to analyse the resting behaviour.

Results

Total of 19,835 potential breeding sites were examined at 13,563 premises, and 18.5% (n = 1856) were positive forAedeslarvae. Distribution ofAe. aegyptiandAe. albopictuswas statistically significant at species level (df = 1;F = 137.134;P < 0.05 GLM) and study setting (df = 2;F = 8.125;P < 0.05).Aedes aegyptibreeding was found mainly in temporary removals (18.8%;n = 34), discarded non-degradables (12.15%;n = 22) and tyres (9.95%;n = 18). Natural (14.7%;n = 246) and temporary removals (13.6%;n = 227) and discarded non-reusable items were the key ovipositing sites forAe. albopictus. In the adult mosquito survey, the majority was comprised ofAe. albopictus(54.5%;n = 999), which denoted exophilic nature (90.8%;n = 758), and 45.5% (n = 835) represented byAe. aegyptimosquitoes who were mainly endophilic (84.3%;n = 842).Aedes aegyptirested on cloth hangings and curtains, followed by the furniture, whileAedes albopictuswas predominant in outdoor vegetation. In both vectors, biting patterns denoted a typical diurnal pattern with two peaks of host-seeking and biting activity in the morning and afternoon.

Conclusions

The majority (80%) of the larval habitats were artificial containers. The use of larvicides for vector control as the prominent measure is questionable since applying these chemicals may target only 20% of the total breeding grounds, which are permanent. The resting places of adult mosquitoes are mainly indoors. Therefore, using thermal space spraying of insecticide may not be appropriate, and indoor residual spraying is recommended as a suitable intervention to target adult mosquitoes. This study warrants a holistic vector control approach for all medically important mosquitoes and insects, ensuring the rational use of finance and resources.

Graphical Abstract