Publications by authors named "Ranil S Dassanayake"

4 Publications

  • Page 1 of 1

Voltage-Gated Sodium Channel () Mutation-Based Pyrethroid Resistance in Populations of Three Endemic Dengue Risk Areas of Sri Lanka.

Biomed Res Int 2021 22;2021:8874092. Epub 2021 May 22.

Molecular Medicine Unit, Faculty of Medicine, University of Kelaniya, Sri Lanka.

Background: Pyrethroid insecticides are widely used in many countries for chemical-based control of . Regardless of their efficacy, the constant use of insecticides has induced insecticide resistance mechanisms, such as knockdown resistance () in mosquitoes. Sri Lankan Vector Controlling Entities (VCE) have been using a variety of pyrethroid insecticides as the primary approach for dengue control. However, development of any resistance among the mosquitoes has been limitedly studied in the country. Therefore, the current study was conducted to evaluate the prevalence of F1534C, V1016G, and S989P mutations among mosquito populations in three dengue endemic high-risk regions of Sri Lanka. . Immature (both pupae and larvae) stages of mosquitoes were collected from Colombo, Gampaha, and Kandy districts of Sri Lanka from February 2018 to December 2019. Polymerase Chain Reaction- (PCR-) based assay for molecular genotyping of mutations was performed to identify the prevalence of mutations in collected populations, separately. The frequencies of the resistant and susceptible kdr alleles were determined by using the Hardy-Weinberg equilibrium.

Results: The populations from Colombo, Gampaha, and Kandy districts showed 46%, 42%, and 22% of F1534C mutation allele frequencies, along with 15%, 12%, and 6% of V1016G mutation allele frequencies, respectively. The mutation allele frequencies of S989 in Colombo, Gampaha, and Kandy districts were 9.5%, 8.5%, and 4.5%, respectively. The wild-type (PP) genotype remained predominant within all the three districts, whereas the homogenous (QQ) mutation genotype occurred only in minority. The abundance of Q allele frequency in mosquitoes was relatively higher for all the three mutations in Colombo.

Conclusions: The findings clearly indicate that long-term insecticide applications and multiple use of pyrethroids have led to the acquisition of mutations, leading to the development of insecticide resistance among local populations, especially in the Colombo and Gampaha districts. Therefore, evaluation of the prevalence levels of these mutations highlights the necessity for shifting towards novel vector control strategies.
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September 2021

Mitochondrial- sequence polymorphism reflects spatial genetic clustering of sibling species E in Sri Lanka.

J Vector Borne Dis 2020 Apr-Jun;57(2):139-146

Center for Biotechnology, Department of Zoology; Genetics and Molecular Biology Unit, Faculty of Applied Sciences, University of Sri Jayewardenepura, Gangodawila, Sri Lanka.

Background & Objectives: Malaria infects around 216 million people annually with estimated 445,000 deaths globally. Anopheles culicifacies is the vector of malaria in Sri Lanka, a complex of five morphologically identical sibling species of which precise identification using DNA-based methods is still under experimentation. This study was carried out in Sri Lanka to observe the utility of BCE-PCR assay based on mitochondrial Cytochrome Oxidase II (COII) developed in India, in sibling species B and E identification in Sri Lanka, to characterize nucleotide and corresponding amino acid sequences of COII region in major vector sibling species E in Sri Lanka and to analyze the spatial distribution pattern of sibling species E in Sri Lanka using microsatellite markers.

Methods: BCE-PCR was carried out for the samples to identify their sibling status. Sequencing of COII region was then carried out to investigate the genetic diversity of Sri Lankan sibling species E, sequences were aligned and compared; microsatellite genotyping was carried out and the spatial clustering pattern was analyzed.

Results: Identification of sibling species B and E using BCE-PCR was confusing due to the heterogeneity in the COII region of sibling species in Sri Lanka. Non-synonymous substitutions were detected in COII gene amongst sibling species E. Spatial distributed two clusters were detected in the studied population.

Interpretation & Conclusion: Existence of genetic variants among sibling species is suggested in Sri Lanka. Further, the pattern of sibling species identification in BCE-PCR was reflected in the spatial clustering of sibling E in Sri Lanka.
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July 2021

Absence of Wolbachia endobacteria in Sri Lankan isolates of the nematode parasite of animals Setaria digitata.

Vet Parasitol 2015 Jan 30;207(3-4):350-4. Epub 2014 Dec 30.

Department of Chemistry, Faculty of Science, University of Colombo, Sri Lanka. Electronic address:

Setaria digitata is an animal filarial parasite with natural hosts of cattle and buffaloes that causes mild disease conditions. Infection of non-permissive hosts such as goats, sheep and horses, by this nematode can cause cerebrospinal nematodiasis that leads to lumbar paralysis and the eventual death of the animals and inflicts considerable economic losses on livestock farmers. Wolbachia are obligate mutualistic endosymbionts for some filarial nematodes and are currently being targeted for the control of diseases caused by these parasites. However, little is known about the occurrence of this endosymbiont in the Setariidae family. In this work, worms collected from infected cattle in Sri Lanka were morphologically identified as S. digitata and tested for the presence of Wolbachia by PCR screening using the WSP- and Wolbachia-specific 16S rRNA and multilocus sequence typing primers that were designed to amplify the gatB, coxA, hcpA, ftsZ and fbpA sequences of Wolbachia. The presence of endobacteria in S. digitata was also examined by whole-mount immunofluorescence staining of the parasites and transmission electron microscopic studies. These analyses did not produce evidence of presence of Wolbachia or any other endosymbiotic bacteria in S. digitata, whereas such evidence was found in Brugia malayi, which was used as a positive control in this study.
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January 2015

Randomly amplified polymorphic DNA fingerprinting: the basics.

Methods Mol Biol 2003 ;226:117-22

Faculty of Medicine, Department of Biochemistry and Molecular Biology, University of Colombo, Sri Lanka.

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November 2003