Epidemiology and Immuno-Molecular analysis of Dengue Outbreak 2016 in nepal

Abstract

The emergence and circulation of viral infection has become one of the major public health concerns in the world. Of those emerging diseases, dengue is a mosquito borne flavivirus mainly prevalent in the tropical and sub-tropical countries. Four serotypes of dengue virus (DENV 1- 4) are globally present. Hundreds of dengue cases are being reported annually and the emergence of this virus with yearly shift in serotypes has become the concern of public health in Nepal. No advanced method besides the Rapid Diagnostic kits are applied for diagnosis in most of the hospitals in Nepal. Rapid tests are not reliable as this coincides with the similar flavivirus infections. The detection of dengue virus infections has great importance for the clinical management of patients, surveillance, and clinical trial assessments in the days to come. Two hundred forty (240) Dengue suspected clinical samples were subjected to Dengue IgM, IgG and NS1 capture ELISA. Indirect IgG ELISA for antibody level detection was done for each sample followed by molecular identification. Viral RNA extraction was done, and cDNA was prepared. After the cDNA was made, Reverse transcriptase PCR(RT-PCR) was performed using D1 and DencomR2 primers. Dengue Serotyping was then done using serotype specific primers. Out of 240 acute dengue cases, 64 % of them were male, 36% female and 2% of the total samples were below age of 10. From the study subjects, 60% were NS1 positive, 33% were IgM positive and 7% were IgG positive. Fourteen samples were positive for all NS1, IgM and IgG ELISA. Calculating the ratio between IgM and IgG, it was found that most of the cases were of primary infection. Antibody level for each serum was calculated and categorised as high, medium and low. The maximum antibody level was found to be 43228.70 and the lowest of 953.53. Altogether, 86 samples were found to be PCR positive for dengue virus. While confirming the serotype prevalence, dengue Serotype-1 was found to be prevalent in the year 2016 in Nepal. Only 37% of the clinically suspected cases were confirmed for dengue virus infection. This implies that confirmatory tests like PCR should be made for the proper diagnosis of the disease and medication to be followed accordingly. To add, ELISA is the preliminary test and RT-PCR is the confirmatory tests for the detection of dengue virus. Key Words: Dengue virus, RT-PCR, ELISA, Re-emergence, Serotyping