Browsing by Author "Wimalasiri, U."

Now showing 1 - 4 of 4

Parasitological screening of vector mosquitoes and molecular biological identification of larval filarial parasites among the wildcaught Mansonia mosquito species at selected areas in the district of Gampaha, Sri Lanka, a re-emerging focus of Brugian filariasis
(University of Kelaniya, 2024) Gunathilaka, N.; Wimalasiri, U.; Chandrasena, N.; Dalpadadu, R.
Brugian filariasis, a disease caused by the Protozoan parasiteBrugia malayi has re-emerged in Sri Lanka after nearly four decades of quiescence. The Brugia malayi that prevailed in Sri Lanka in the past was the nocturnal periodic human strain transmitted by mosquitoes of the genus Mansonia. The objective of the present study was the precise identification of vector mosquitoes and parasites of the current onset of the disease. Entomological surveys were performed during September/October 2021 in Ragama Medical Officer of Health area using cattle-baited net traps. Mansonia sp. mosquitoes were dissected to detect the presence of larvae of the parasite. The lysate of dissected mosquitoes positive for larvae was used for the extraction of genomic DNA of the parasite, which was subjected to Polymerase Chain Reactions (PCR) aimed at molecular speciation using pan-filarial primers specific for the internal transcribed spacer region two (ITS2) of the ribosomal DNA. A total of 1060 mosquitoes were tested, and that included seven mosquito species belonged to four genera. Culex gelidus (n=602; 56.8%) was detected as the predominant mosquito species followed by Armigeres subalbatus (n=420; 39.6%) Cx. tritaeniorynchus (n=2; 0.2%) and Anopheles nigerrimus (n=4; 0.4%). Mansonia spp. accounted for 2,7% of the total mosquito sample and among them, the presence of Mansonia annulifera was 1,2% of the total (n=20), Ma. uniformis was 0.9% (n= 10) and Ma. Indiana was 0.2% (n= 2). About 18.7% (n=6) of Mansonia mosquito collection was positive for filarial larvae. Among them, 15.6% (n=5) was Mansonia annulifera while (3.1%; n=1) was Ma. uniformis. The PCR products of all tested samples corresponded to the band size of 625 bp, specific to B. malayi confirming the identity of the parasite. Mansonia annulifera and Ma. uniformis were confirmed as vectors of the re-emerged B. malayi (nocturnally sub-periodic) in Gampaha district. The role of other mosquito vector species would require investigation by vector incrimination and xenomonitoring-based approaches.
Presence of leishmaniasis causing agent, Leishmania donovani, in biting midges (Culicoides sp) at a disease endemic area of Sri Lanka: Could it be a probable vector?
(Faculty of Graduate Studies, University of Kelaniya Sri Lanka, 2022) Wijerathna, T.; Wimalasiri, U.; Wijegunawardena, A.; Gunathilaka, N.; Rodrigo, W. W. P.
Biting midges are a group of dipteran insects of the family Ceratopogonidae. Some species of biting midges are known to be vectors for filaria parasites that infect humans, and some are known to be vectors of viruses that infect livestock. Evidence suggests that biting midges may be a potential vector for Leishmania parasites in other countries. Biting midges are found in high densities in leishmaniasis endemic regions of Sri Lanka. This high density and biting nuisance suggest that these insects may have a possible role as secondary vectors (if not primary vectors) for leishmaniasis in these areas. The first criterion of leishmaniasis vector incrimination is the detection of parasites from the suspected vectors. Therefore, the present study examined the Leishmania donovani parasites circulate within biting midge populations at a leishmaniasis endemic area in Sri Lanka. The study was conducted in Medawachchiya Medical Officer of Health area in Anuradhapura District, Sri Lanka. Biting midges were collected using cattle baited net traps during December 2021. The collected specimens were identified using morphological identification keys. The specimens were surface sterilized using 70% ethanol and the DNA was extracted from the fly using MightyPrep reagent for DNA (Takara, Japan). The parasite DNA was detected using a Polymerase Chain Reaction (PCR) using Leishmania donovani specific primers that target kinetoplast minicircle gene. The amplicons were visualized under UV light after running on a 2% agarose gel stained with ethidium bromide. A total of 42 biting midges were collected and all of them were females. The collection consisted of a single species similar to Culicoides imicola in morphology. The gel electrophoresis and subsequent UV visualization indicated that two of the samples were positive for L. donovani DNA indicating a parasite circulation rate of 4.76% within the wild biting midge population. The results of the current study suggest that the L. donovani, the main causative agent of leishmaniasis in Sri Lanka, circulates within biting midge populations indicating a possibility of this species being a vector for leishmaniasis in Sri Lanka. According to the World Health Organization (WHO) criteria for leishmaniasis vector incrimination, the detection of the parasites within the insect is the first step. Further studies to assess the luxuriant growth of the parasite within midge midgut and experimental transmission using animal models are needed to confirm the vector status. Considering the medical and veterinary importance, the studies on biting midges of Sri Lanka are recommended.
The presence of strongyloidiasis and associated risk factors in patients undergoing treatment at the National Cancer Institute, Maharagama, Sri Lanka
(Sri Lanka Medical Association, 2023) Weerasekera, C.J.; Menike, C.W.; Wimalasiri, U.; Wijerathna, T.; Jayathilake, D.C.C.; Somawardane, U.A.B.P.; Saravanamuttu, U.; Yoganathan, N.; Perera, N.; Gunathilaka, N.; de Silva, N.R.; Wickremasinghe, D.R.
INTRODUCTION: Strongyloides stercoralis can cause severe disease in the immunocompromised. Without a proper gold-standard diagnostic technique, strongyloidiasis is scarcely studied both globally and locally. OBJECTIVES: We aimed to estimate the prevalence of strongyloidiasis among immunocompromised adult patients and to identify risk factors. METHODS: This study was carried out between February to October 2022. A faecal sample and 2 ml of venous blood were collected from consented patients. Direct faecal smear, agar plate, Harada-Mori and Charcoal cultures were performed on the faecal samples. Qualitative Polymerase Chain Reaction (PCR) was performed on selected faecal samples using S. stercoralis targeting ITS1 region. Strongyloides IgG ELISA was carried out on the serum samples using DRG Strongyloides IgG ELISA kit. RESULTS: Collectively, 144 patients (males = 68, females = 76) provided blood/faecal sample or both. Relevant to strongyloidiasis-associated symptoms, some patients had diarrhoea (n=12) and eosinophilia (n=11). Some of them (n=74) had occupational or recreational exposure to soil as potential risk factors. Overall, 24 patients were positive for strongyloidiasis from one or more diagnostic method (5 PCR and 19 ELISA). There were zero culture or direct smear positives. There was no significant association between disease positivity with either of the clinical features or risk factors. CONCLUSION: The prevalence of strongyloidiasis in patients with malignancies was 16.66%. Strongyloidiasis is existent in the immunocompromised in Sri Lanka even in the absence of suggestive clinical features or regular exposure to risk factors. Screening immunocompromised patients with sensitive techniques such as PCR for timely diagnosis and treatment is recommended.
Therapeutic potential of melittin peptide: major pain-producing substance of european honeybee (apis mellifera) venom against several communicable and non-communicable diseases
(The Library, University of Kelaniya, Sri Lanka, 2023) Gunathilaka, N.; Wimalasiri, U.; Wijerathna, T.
Invertebrates have evolved to produce peptide compounds to ensure success in prey capture and defence against potential enemies. Some of these compounds have become highly potent therapeutic compounds used in medicine. Melittin, a peptide extracted from bee venom, has emerged as a promising therapeutic option that has the potential to obviate the disadvantages of existing therapeutics against several communicable and non-communicable diseases. This article reviews peer-reviewed journal articles to provide a conspectus of current research on the therapeutic uses of melittin. Melittin is predominantly an antimicrobial peptide and shows therapeutic potential against several non-communicable diseases, including cancers, inflammatory diseases and diabetes. Furthermore, it acts against a range of protozoan parasites that infect humans. The biological activities of melittin are mainly achieved via cytotoxicity and downregulation of certain metabolic pathways. The ability to conjugate with other compounds and nanoparticles to improve the effectiveness is an added advantage in melittin-based therapy. The antiparasitic properties and relatively shorter sequence enable the use of this molecule in biological control methods such as paratransgenesis. This is further facilitated by the ability to express in an inactive form to be activated later. Melittin is a peptide with a broad therapeutic potential. The supplementation of the existing knowledge with studies on effective and specific delivery mechanisms will enable the effective use of this peptide against many communicable and non-communicable diseases.