| dc.description.abstract | The Kole wetlands in Thrissur, Kerala, are a strip of shallow water that acts as an
intermediate zone between terrestrial and marine ecosystems. They keep the water
level between 0.5 to 1 meter below sea level and are situated in Kerala's central
region, covering an area of 10187 hectares, spanning across the Mukundapuram,
Chavakad, and Thrissur Taluks of the Thrissur District. These designated Ramsar
sites are a unique part of the Vembanad-Kole wetland ecosystem. The area remains
submerged under flood water for about six months each year, and during the Post and
Pre-Monsson seasons, paddy and other agricultural practices are carried out.
Additionally, several anthropological activities such as fishing, bird watching, clay
mining, building construction, research, and recreation take place in the Kole lands.
The Kole wetlands in Thrissur, Kerala, are a rich wetland ecosystem with a diverse
range of species. Mosquitoes are an essential part of this ecosystem and are one of the
most significant insect disease vectors globally.
Mosquitoes thrive and reproduce successfully in wetlands due to the availability of
suitable breeding habitats and conducive environments. In Kerala, there has been a
significant increase in the outbreak of mosquito-borne diseases in recent years. The
presence of mosquitoes in wetlands poses a substantial risk of disease transmission to
visitors and workers, thereby becoming a matter of public health concern. It is
essential to accurately identify, map, and document the mosquito population and the
factors that influence their proliferation to address this issue. This is the initial step in
developing an effective vector control strategy.
The major study objectives were the diversity study of available mosquito species in
the Kole wetlands of Thrissur, Kerala, and compare the susceptibility of Aedes
albopictus and Culex
quinquefasciatus against
conventional
insecticides.To understand the mosquito diversity, conventional and molecular identification of
available mosquito species, their influencing factors, and GIS preparation of identified
mosquito species were done in this study. The larval and adult mosquito populations. ecies were done in this study. The larval and adult mosquito populations
XXVIIIwere collected by direct sampling method and identified using systematic keys. A
stereo zoom microscope (Leica-M205C) was used for the identification in the
laboratory. Dominance D, Simpson's 1-D, Shannon -H, Evenness H/S, Margalef,
Biodiversity index, and Berger-Parker indices demonstrated the alpha diversity of the
study area.
The study involved comparing two sites using the Jaccard and Sorenson Diversity
indices and conducting Gamma diversity analysis. The 'PAST' software was utilised
for the diversity analysis. The study area had three distinct seasons, namely Pre-
monsoon, Monsoon, and Post-monsoon, each lasting four months. Monthly sampling
was conducted over a period of two years from each sampling location, and the data
collected were recorded. The number of mosquitoes collected in different seasons was
analysed using a one-way ANOVA test to determine any variation. GPS readings
were taken for each sampling location, and the mosquito species were recorded during
the diversity study period. The available mosquito data were used to prepare a GIS
map using the QGIS software. Additionally, water samples were collected from larval
habitats during the monthly sampling.
During the study, water samples were collected and analysed to investigate the
relationship between mosquito diversity and the physical and chemical characteristics
of the larval habitats. The physico-chemical parameters, including temperature, pH,
turbidity, conductivity, and chemical parameters, including total dissolved solids,
dissolved oxygen, alkalinity, hardness, chloride, and salinity, were recorded
simultaneously with the collection of water samples. The water samples were
transported to the laboratory in sterile containers for chemical analysis, and the
standard methods recommended by APHA were used to test the water parameters. To
ensure the accuracy of identification, molecular identification through CO1 gene
sequencing and phylogenetic analysis was conducted. A total of 20 mosquito species
from five genera were collected and identified from various locations during the study
period. GIS map of 3 sampling sites prepared with these identified mosquito species.
The presence and abundance of mosquitoes vary in different seasons. Almost all
mosquitoes except Ph. cogilli and Ma. bonneae were collected in either two or three
seasons in a year. ANOVA test reveals that nearly all mosquitoes other than four
species (An. stephensi, Ph. cogilli, Cx. bitaeniorhynchus, and Ma. bonneae) showed a significant variation in different seasons. Species with no variation were either present
in only one season (Ph. cogilli and Ma. bonneae) or had a uniform distribution in two
(Cx. bitaeniorhynchus) or three (An. stephensi) seasons.
In this study, we tried to analyse the correlation between the physico-chemical
parameters of water samples from different breeding habitats and mosquito diversity.
Altogether 20 mosquito species were collected from different breeding habitats during
the study period, and values of 10 water quality parameters were recorded. pH,
Turbidity, Conductivity, TDS, Hardness, and Chloride exhibits significant correlation
with the total number of mosquitoes collected. The rest of the parameters
(Temperature, DO, Alkalinity, Salinity) do not correlate with the number of
mosquitoes collected. Out of 20 species discovered, 9 mosquitoes express some
correlation between the physico-chemical parameters of water samples from their
breeding habitats.
DNA sequencing, molecular identification, and phylogenetic analysis were done with
these collected species for species confirmation. Final nucleotide sequences of every
collected species were deposited to NCBI GenBank and obtained an accession
number. ORIGIN Genomic DNA isolation Kit used for DNA extraction. Agarose gel
electrophoresis was conducted for the confirmation of the presence of DNA. The
amplification reaction was performed using a DNA thermal cycler (Takara). The
purified PCR product was sequenced using Sanger’s sequencing method at Sci
Genom Labs Private Ltd., Cochin, and IISc Bengaluru with ABI 3730XL automated
sequencer. The trimmed COI sequences of forward and reverse obtained were aligned
using ClustralW. The Final sequence was searched in NCBI BLAST for species
confirmation. The partial COI gene sequence was deposited in GenBank (NCBI) for
worldwide accession, and it can be used as a molecular barcode generation. Final
nucleotide sequences were analysed using MEGAX to study phylogenetic
relationships.
Insecticide
susceptibility
of Ae.
albopictus and Cx.
quinquefasciatus against
conventional insecticides were checked by the standard WHO method. Comparison
analysis of lethal concentration values of field and laboratory strain Ae. albopictus
and Cx. quinquefasciatus revealed that laboratory strain was more susceptible than
field strain mosquitoes in every insecticide. The remarkable difference in LC 50 values between strains of the same species may be the product of the evolution of insecticide
resistance. This trait may be essential as a biological indicator of insecticide
pollution. In the context of tested insecticides, synthetic pyrethroids were the most
influential group of insecticides, and carbamate was the least effective. The
insecticide efficacy varies, and the decreasing order of susceptibility follows Lambda-
cyhalothrin > Deltamethrin > Temephos > Malathion > Propoxur. This study will
provide information about available mosquito species and the prediction of mosquito-
borne disease outbreaks in the Kole wetlands of Thrissur. The findings from the
susceptibility test conducted on the identified mosquito species can aid in the efficient
management of mosquito populations by minimizing the use of pesticides. | en_US |
