Browsing by Author "Jayasooriya, D.H.S.W."

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    Aedes albopictus the “underrated” Asian Tiger
    (University of Kelaniya, 2010) Jayasooriya, D.H.S.W.; Gunawardene, Y.I.N.S.; Manamperi, A.; de Silva, H.J.; Abeyewickreme, W.
    Introduction The mosquito Aedes aegypti was thought to be the main vector responsible for virtually all dengue epidemics; while Aedes albopictus was considered a vector in which the virus is maintained but does not cause epidemics. Objective The study was conducted covering three endemic districts in Sri Lanka to determine the role of genus Aedes during dengue transmission. Methods and Material Mosquitoes were collected within a 350m radius from the location of the positive patients. Heads and abdomens of 63 pools were tested for DENV RNA with and RT-PCR-LH-(P32) assays Results Discussion Ae. albopictus was present in majority of the locations in all districts surveyed. Ae. albopictus was found in 13/17 (76.47%), 24/25 (96%)and 19/22 (86.36%) sites in Colombo, Gampaha and Kurunegala respectively. The RT-PCR-LH-(P32) assays indicated that 5/25 (20%) sites in Gampaha, 2/17 (11.76%) in Colombo and 6/22 (27.27%) in Kurunegala were positive for DENV. In Gampaha and Colombo there were 3 and 1 of DEN-2 positive pools respectively, while there were 2 and 1 of DEN-3 positive pools respectively. A higher number of positive pools (4/1or 21.05%) for DEN-1 and 1/1(5.26 %) for DEN-4 were found in Kurunegala. In Kurunegala one pool was positive for both DEN-2 and DEN-4 indicating the circulation of multiple serotypes within close proximity. Moreover one of the three DEN-2 positive pools in Gampaha consisting of only male Ae. albopictus mosquitoes is supportive of the belief of vertical transmission of DENV. In a DEN-4 positive location in Kurunegala HI was found to be10%, BI= 1and CI= 5.88 %while anotherDEN-2 positive site in Wattala showed HI of 5.55%and a BI of 5.55 suggesting active transmission. The abundance of Ae. albopictus in all districts and the findings indicating that100% of the positive pools were made of Ae. albopictus in this study highlights the importance of Ae. albopictus in the transmission dynamics dengue. The ability of Ae. albopictus to be infected with low viremia and the degree to which it permits replication within the mosquito itself could have an impact on the transmission and these verity of the disease. Co-circulation of two or more serotypes in a single pool or in different pools of mosquitoes within the same district is suggestive of hyper endemic transmission dengue in the three districts. The greater susceptibility of Ae. albopictus to infection by DENV is said to lead to greater virus adaptation. Sri Lanka as a whole would be at serious risks for multiple outbreaks in future. Our results indicate that Ae. albopictus is more efficient in dengue transmission than previously thought. The results shed light on the efficiency of Ae. albopictus as a vector in transmitting DENV in the absence or low abundance of Ae. aegypti in Sri Lanka. The present study suggests that Ae. albopictus sp is underrated in terms of transmission potential during peak transmission periods of dengue in Sri Lanka. Key words: RT-PCR-LH-(P32) RT-PCR-Liquid Hybridization with P32 radio isotope, HI-House hold Index, BI- Breteau Index, CI-Container Index,DENV-Dengue Virus Authors wish to acknowledge the financial assistance rendered by the NSF Sri Lanka (GrantNo:SIDA/2006/BT/02)and the IAEA (Grant NoTC SRL 6/028).
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    A Comparative field study of novel commercial Antigen Detection Enzyme-Linked Immunosorbent Assay (ELISA) with Reverse Transcription Polymerase Chain Reaction (RT- PCR) assay for early definitive laboratory diagnosis of dengue viral infection in Sri Lanka
    (Sri Lanka Association for the Advancement of Science, 2007) Hapugoda, M.D.; Jayasooriya, D.H.S.W.; Gunawardene, Y.I.N.S.; Wellawaththage, C.; Premaratna, R.; Abeyewickreme, W.
    Dengue is an important mosquito borne viral infection in South East Asia. Early definitive laboratory diagnosis of infection would help in management of patients and reducing the case fatality rate. The objective of this study was to determine the accuracy of novel commercial Antigen Detection Enzyme-Linked Immunosorbent Assay (ELISA) using Non Structural protein 1 (NS1) (Bio Rad) for early definitive laboratory diagnosis of dengue infection under field conditions in Sri Lanka. A panel of acute serum samples collected from 99 patients clinically suspected of having dengue fever (<5 days) warded at the North Colombo Teaching Hospital, Ragama, Sri Lanka were used for the present study. Serum samples were tested using Antigen Detection ELISA according to the method described by the manufacturer. Results of this novel assay were compared with RT-PCR assay using Chi-squared test. Two variables were analyzed at a 95% confidence interval and P value <0.05 was considered as significant. Twenty two and 65 patients were positive and negative, respectively, for dengue infection by both assays. Nine patients were confirmed as dengue by the Antigen Detection ELISA only. Three patients were confirmed as dengue by RT-PCR assay only. Antigen detection ELISA showed 88% of agreement with the RT-PCR assay. According to the Chi-squared test, there was no significant difference between the two assays for early diagnosis of dengue infection (?2=46, P=0.0000). Novel commercial Antigen Detection ELISA kit (Bio-Rad 72830) can be used for early definitive laboratory diagnosis of dengue infection in Sri Lanka under field conditions. Acknowledgement: the International Atomic Energy Agency (SRL 06/28) for technical co-operation and APCOT Marketing LTD, Sri Lanka for supplying Antigen detection ELISA kits.
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    Investigation of dengue virus serotypes and genetic variability in relation to disease severity and transmission
    (University of Kelaniya, 2012) Jayasooriya, D.H.S.W.
    Sri Lanka has been experiencing more or less periodic dengue outbreaks. METHODOLOGY: Acute phase blood samples were collected from patients clinically suspected of having dengue as determined by the WHO criteria (WHO 1997) within 4 days of onset of fever, from the hospitals in the Sri Lankan districts of Colombo, Gampaha, Kandy, Kurunegala throughout the year. Dengue vector Aedes mosquitoes were colleted from the above geographical areas where positive cases were reported, Pooled mosquitoes and sera were subjected to analysis. RT-PCR and RT-PCR-LH established methods were used to detect dengue virus. Envelope glycoprotein gene (E gene) of DENY serotypes were sequenced and were compared with available sequences representative of the Americas, Oceania, Africa, South Asia, East Asia, and the Middle East. Deduced amino acid sequences of the Present Study Sri Lankan isolates (PSSL-iso) were compared with the past Sri Lankan isolates and South Asian isolates. Sequences of DF an DHF patients were compared as well. Clinical symptoms among serotypes in relation to severity were investigated. RESULTS AND DISCUSSION: In each district a minimum of 3 serotypes were in circulation. DEN-2 and DEN-3 were the most abundant .There was greater degree of conservation among the geographical isolates of DEN-2 compared to that of DEN-3. Evolutionary pressures act on the two serotypes differently despite both being co-transmitted within close proximities. Specific substitutions or substitution patters which could differentiate between DF and DHF/DSS were not found. However phylogentic analysis in DEN-3 revealed clustering of five isolates which showed an increased tendency to be associated with DHF or severe form of disease than the rest which harboured amino acid substitution Asn383^Lys383 on the lateral ridge of ED-III domain within the "informative sites" or sites known as unique conserved site for G-III. DEN-2 isolates belonged to the Cosmopolitan genotype were shown to have more of an Indian ancestry than a Sri Lankan one as they were closer in terms of phylogeny to the Indian origin isolates than to the previously existed Sri Lankan isolates. DEN-2 harboured unique Ile226 lying within the Previously Determined Antigenic Regions (PDAR) a substitution which was not present in any of the South Asian isolates analysed. Simultaneous co-infections by DEN-2& DEN-3 and DEN-4 &DEN-3 surprisingly lead to a reduction in disease severity. The results indicated that it is not in fact the number of amino acid substitutions which could determine the severity of disease but the type of substitution and the position within the domains which they occur. Most abundant vector species found in all districts was Aedes dlbopictus and all pools positive for DENY were Aedes albopictus pools. Moreover positive DENY transmission was observed in localities where Breteau index (BI) was as less as 5.55 suggesting the importance of the role of A .albopictus an "underrated vector". The findings in total suggest that all districts studied are hyperendemic to dengue and Sri Lanka is highly susceptible to successive outbreaks in the future while the difference of evolutionary pressures acting on the predominant serotypes and the reasons said above are likely to shape the nature of future outbreaks
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    Serotype distribution of dengue in Gampaha District, Sri Lanka
    (Faculty of Tropical Medicine, Mahidol University, 2008) Jayasooriya, D.H.S.W.; Gunawardene, Y.I.N.S.; Manamperi, A.; Hapugoda, M.D.; Premaratna, R.
    Dengue Virus (DENV) affecting millions of people mainly in the tropical and subtropical regions is a positive sense RNA virus which exists in four different serotypes (DENV1-4) and several subtypes. All four serotypes have been found in Sri Lanka. The objective of the study was to determine the DENV serotype distribution in patients and mosquitoes of Gampaha district. Serum was isolated from acute phase blood samples collected from dengue suspected patients during the febrile period. Mosquitoes were collected from different locations where dengue confirmed cases were reported. Pooled and crushed mosquito heads and serum samples were separately subjected to RNA extraction, RT-PCR, semi nested PCR with Dengue serotype specific primers and solution hybridization with Phosphorous 32 labeled probes respectively. Out of 93 patients, 34 were positive for DENV out of which 19 corresponded to DENV2, 5 to DENV3 and 10 were co-infected with DENV2 and DENV3. Of the positive infections corresponding to serotypes 2, 3, 2-3 co-infected; 7/19 (36.8%), 3/5(60%), 0/10 (0%) had developed dengue haernorrhagic fever respectively Among 14 mosquito pools, 5 were positive of which 3 were infected with DENV2 and 2 with DENV3. It was observed that although both DENV2 and DENV3 circulate among patients and in mosquitoes in Garnpaha District, DENV2 was predominant in both. Only Aedes albopictus 'presence in all localities was significant. A greater percentage of severe form of the disease among DENV3 infected patients was observed while a less severe form of the disease was observed in DENV2 and DENV3 co-infected patients