A longitudinal research carried out between February 2021 and June 2022 in Bengaluru metropolis has discovered how urbanisation impacts mosquito ecology and the way mosquito species variety and abundance modifications throughout macro and microhabitats. The research discovered that the standard of breeding websites determines the abundance and distribution of mosquito species, particularly those that trigger dengue.
While water containers, discarded grinding stones, tyres and plastic containers served as good man-made larval habitats, the way in which mosquitoes work together with larval habitats in numerous macrohabitats did play an essential function in figuring out mosquito variety and abundance. Whereas plantations, owing to various habitat varieties, proved to have excessive mosquito species variety and richness in contrast with high-density populated areas within the metropolis, even barren lands did have microhabitats conducive for breeding.
The outcomes of the research, posted within the medRxiv preprint server, are but to be peer-reviewed.
In all, six macrohabitats have been studied. These embrace: barren lands, lakes and their environment, plantations, and excessive dense, medium dense, and low dense urban areas. A complete of 48 index grids (fastened) have been chosen with eight replicates of every macrohabitat sort, which have been surveyed throughout all 4 seasons — dry (January-March), pre-monsoon (April-June), monsoon (July-September), post-monsoon (October-December). In addition, 98 random grids representing a macrohabitat sort have been surveyed throughout two seasons (April-June and July-September). This allowed sampling mosquitoes in diversified ecological niches within the metropolis whereas surveying fastened grids on a seasonal foundation. In every macrohabitat (resembling grinding stone, tyres, discarded plastic containers, tree holes) the researchers visually inspected for the presence of mosquito larvae.
A complete of 8,717 container breeding websites have been inspected by the researchers and 1,619 mosquito larvae have been collected from six macrohabitats and 9 microhabitats. Of these practically 1,300 mosquitoes emerged comprising 16 species from 5 genera. Aedes aegypti was essentially the most dominant species (55%), adopted by Aedes albopictus (28%).
While the WHO protocols are restricted to door-to-door larval surveillance and in search of mosquito larvae in containers, the research has demonstrated that urban environments with non-residential areas too harbour very best breeding websites. Any programme aimed toward decreasing dengue transmission must also consider neighbourhood surveillance to forestall and management the rising risk of Aedes species. “We found landscape ecology drives mosquito diversity and abundance even at a small spatial scale, and this could be affecting the localised dengue outbreaks,” says Dr. Farah Ishtiaq from the Bengaluru-based Tata Institute for Genetics and Society, and the corresponding writer of the preprint.
“We found man-made artificial containers accounted for over 90% of larval habitats. Water storage containers came out as the most common breeding habitat for Ae. aegypti, but since the containers are actively in use, they serve only as ephemeral habitats due to high disturbance,” she says. The shock discovering was not simply the choice for discarded grinding stones as breeding websites however these microhabitats containing the very best prevalence of Aedes larvae. “Discarded grinding stones showed high prevalence of Ae. aegypti and Ae. albopictus larvae. But the prevalence in stagnant water was less as these are open water bodies and more polluted,” Dr. Ishtiaq says.
While plastic containers resembling cups and coconut shells have been ample, discarded tyres weren’t. For Ae. aegypti, tyres and coconut shells did function very best habitats however have been restricted in numbers. In the case of Ae. Albopictus, albeit at low frequency, plant axils and tree holes served as breeding websites whereas coconut shells didn’t.
The heterogeneity in macrohabitat varieties was masked by the man-made microhabitats, which have been ubiquitous in all of the six landscapes studied, and these microhabitats performed key ecological roles. Habitat choice by the 2 Aedes species seemed to be pushed on the microhabitat degree.
Body measurement of each Aedes species confirmed a variation in wing size throughout microhabitat and macrohabitat varieties. Mosquitoes that emerged from the discarded grinding stones had considerably bigger wing size than discarded containers or coconut shells. While giant physique measurement females can fly lengthy distances, smaller females can not fly farther and require a number of meals. The research discovered that when each Aedes species co-existed in a microhabitat, Ae. albopictus all the time ended up with decreased wing size.
“Our study relies on outdoor surveillance which highlights the importance of ‘neighbourhood surveillance’ in public places which can help in real-time forecasting of dengue cases in urban areas,” she says. “Our findings show that sampling strategies for mosquito surveillance must include urban environments with non-residential locations. And dengue transmission reduction programmes should focus on ‘neighbourhood surveillance’ as well to prevent and control the rising threat of Aedes-borne diseases.”
