Impact of salinization and pollution of groundwater on the adaptation of mosquito vectors in the Jaffna peninsula, Sri Lanka

Surendran, Sinnathamby N.; Senthilnanthanan, Meena; Jayadas, Tibutius T. P.; Karunaratne, S.H.P.P.; Ramasamy, Ranjan

doi:10.4038/cjs.v49i2.7734

Cited by 6 publications

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“…aegypti in the peninsula. However, the present findings reinforce our previous recommendations [ 7 , 44 ] that dengue vector control measures in the Jaffna peninsula, which are currently only directed towards FW habitats, need to be extended to BW habitats.…”

Section: Discussionsupporting

confidence: 91%

“…The data suggest varying preference for different types of habitats among the three Aedes species that warrants more detailed investigation than was possible in our study. Our findings suggest that Aedes vectors in the Jaffna peninsula are evolving to adapt to anthropogenic changes in the environment [ 5 , 7 ]. In the Jaffna peninsula, Ae.…”

Section: Discussionmentioning

confidence: 99%

“…The entire human population of the peninsula relies on groundwater extracted from the aquifers to meet all water needs (e.g. drinking water, and water for domestic, agricultural and industrial needs), but this water is becoming increasingly brackish [ 4 , 6 , 7 , 40 – 43 ]. The water in many domestic wells in the coastal areas nearby Jaffna city are brackish and yet support the preimaginal development of Ae.…”

Section: Discussionmentioning

confidence: 99%

“…The annual average temperature is 31.5 °C, and average relative humidity is 74.4%, with the temperature slightly decreasing and relative humidity increasing more markedly during the monsoon. The peninsula is undergoing rapid salinization of its groundwater due to the incursion of sea water as a result of unsustainable rates of water extraction from freshwater aquifers and rising sea levels [ 4 , 6 , 7 ]. Dengue has been present in Sri Lanka since the beginning of the 20th century, with a high prevalence in the Jaffna district in recent years; there have been approximately 200 reported cases of dengue per 100,000 persons in the district in 2019 [ 8 , 9 ].…”

Section: Introductionmentioning

confidence: 99%

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Aedes larval bionomics and implications for dengue control in the paradigmatic Jaffna peninsula, northern Sri Lanka

et al. 2021

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Background The larval bionomics of Aedes across the Jaffna peninsula in northern Sri Lanka was investigated to obtain information needed for developing more effective larval source reduction measures to control endemic arboviral diseases. Methods The habitats of preimaginal stages of Aedes mosquitoes were surveyed, and ovitrap collections were carried out in densely populated areas of the Jaffna peninsula. Aedes larval productivities were analysed against habitat characteristics, rainfall and dengue incidence. Adults emerging from collected larvae were tested for dengue virus (DENV). Results Only Aedes aegypti, Ae. albopictus and Ae. vittatus were identified in the field habitat collections and ovitraps. Aedes aegypti was the predominant species in both the field habitat and ovitrap collections, followed by Ae. albopictus and small numbers of Ae. vittatus. Tires and open drains were the preferred field habitats for Ae. aegypti, although larval productivity was higher in discarded plastic containers. The three Aedes species differed in field habitat preferences. Concomitant presence of the three Aedes species was observed in the field habitats and ovitraps. Larval productivities were inversely correlated with the salinity of the field habitat. Rainfall in the preceding month significantly correlated with larval productivity in the field habitats. DENV serotype 2 was detected in Ae. aegypti collected from ovitraps in the city of Jaffna. High Breteau, House and Container indices of 5.1, 5.1 and 7.9%, respectively, were observed in the field habitat surveys and ovitrap indices of up to 92% were found in Jaffna city. Conclusions Aedes larval indices in populated areas of the peninsula showed a high potential for dengue epidemics. Unacceptable littering practices, failure to implement existing dengue control guidelines, vertical transmission of DENV in vector mosquitoes and preimaginal development in brackish water and open surface drains, as well as in domestic wells that provide potable water, are serious constraints to the current Aedes larval source reduction methods used to control dengue in the Jaffna peninsula. Similar shortcomings in arboviral disease control are likely present in other resource-constrained tropical coastal zones worldwide.

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Section: Discussionsupporting

confidence: 91%

Section: Discussionmentioning

confidence: 99%

Section: Discussionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Aedes larval bionomics and implications for dengue control in the paradigmatic Jaffna peninsula, northern Sri Lanka

et al. 2021

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“…albopictus in BW increases the potential for arboviral disease transmission which can be exacerbated by rising sea levels due to global warming causing greater salinization of inland waters [ 19 – 23 ]. The 1130km 2 Jaffna peninsula in northern Sri Lanka is undergoing rapid salinization of its groundwater aquifers and coastal wells due to the incursion of sea water [ 20 , 24 ]. Genetic changes for salinity tolerance can therefore rapidly spread among Ae.…”

Section: Introductionmentioning

confidence: 99%

Transcriptomic, proteomic and ultrastructural studies on salinity-tolerant Aedes aegypti in the context of rising sea levels and arboviral disease epidemiology

et al. 2021

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Background Aedes aegypti mosquito, the principal global vector of arboviral diseases, lays eggs and undergoes larval and pupal development to become adult mosquitoes in fresh water (FW). It has recently been observed to develop in coastal brackish water (BW) habitats of up to 50% sea water, and such salinity tolerance shown to be an inheritable trait. Genomics of salinity tolerance in Ae. aegypti has not been previously studied, but it is of fundamental biological interest and important for controlling arboviral diseases in the context of rising sea levels increasing coastal ground water salinity. Results BW- and FW-Ae. aegypti were compared by RNA-seq analysis on the gut, anal papillae and rest of the carcass in fourth instar larvae (L4), proteomics of cuticles shed when L4 metamorphose into pupae, and transmission electron microscopy of cuticles in L4 and adults. Genes for specific cuticle proteins, signalling proteins, moulting hormone-related proteins, membrane transporters, enzymes involved in cuticle metabolism, and cytochrome P450 showed different mRNA levels in BW and FW L4 tissues. The salinity-tolerant Ae. aegypti were also characterized by altered L4 cuticle proteomics and changes in cuticle ultrastructure of L4 and adults. Conclusions The findings provide new information on molecular and ultrastructural changes associated with salinity adaptation in FW mosquitoes. Changes in cuticles of larvae and adults of salinity-tolerant Ae. aegypti are expected to reduce the efficacy of insecticides used for controlling arboviral diseases. Expansion of coastal BW habitats and their neglect for control measures facilitates the spread of salinity-tolerant Ae. aegypti and genes for salinity tolerance. The transmission of arboviral diseases can therefore be amplified in multiple ways by salinity-tolerant Ae. aegypti and requires appropriate mitigating measures. The findings in Ae. aegypti have attendant implications for the development of salinity tolerance in other fresh water mosquito vectors and the diseases they transmit.

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Resistance to the larvicide temephos and altered egg and larval surfaces characterize salinity-tolerant Aedes aegypti

Sivabalakrishnan

Murugathas

Tharsan

et al. 2023

Sci Rep

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Aedes aegypti, the principal global vector of arboviral diseases and previously considered to oviposit and undergo preimaginal development only in fresh water, has recently been shown to be capable of developing in coastal brackish water containing up to 15 g/L salt. We investigated surface changes in eggs and larval cuticles by atomic force and scanning electron microscopy, and larval susceptibility to two widely-used larvicides, temephos and Bacillus thuringiensis, in brackish water-adapted Ae. aegypti. Compared to freshwater forms, salinity-tolerant Ae. aegypti had rougher and less elastic egg surfaces, eggs that hatched better in brackish water, rougher larval cuticle surfaces, and larvae more resistant to the organophosphate insecticide temephos. Larval cuticle and egg surface changes in salinity-tolerant Ae. aegypti are proposed to respectively contribute to the increased temephos resistance and egg hatchability in brackish water. The findings highlight the importance of extending Aedes vector larval source reduction efforts to brackish water habitats and monitoring the efficacy of larvicides in coastal areas worldwide.

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Impact of salinization and pollution of groundwater on the adaptation of mosquito vectors in the Jaffna peninsula, Sri Lanka

Cited by 6 publications

References 0 publications

Aedes larval bionomics and implications for dengue control in the paradigmatic Jaffna peninsula, northern Sri Lanka

Aedes larval bionomics and implications for dengue control in the paradigmatic Jaffna peninsula, northern Sri Lanka

Transcriptomic, proteomic and ultrastructural studies on salinity-tolerant Aedes aegypti in the context of rising sea levels and arboviral disease epidemiology

Resistance to the larvicide temephos and altered egg and larval surfaces characterize salinity-tolerant Aedes aegypti

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