Serotype distribution of dengue in Gampaha District, Sri Lanka

Abstract

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