Abstract:
Dengue incidence has been dramatically increasing in the recent years. Epidemiological surveillance based on the evolution dynamics of circulating-dengue viruses, including environmental condition, can be used to determine the trend in dengue transmission, which has led to the prediction and planning of effective control approach. The objective is to focus on the mutation and seasonal evolutionary analysis of dengue virus existing in the highly endemic area through mosquitoes and local residents. Samut-Sakhon province was selected since it is considered as one of the top-ten province of having the highest annual morbidity in Thailand. Entomological collection was undertaken over-three seasons, during 2012 to 2013 and in early rainy season in 2013. The EDTA-blood was drawn from local asymptomatic volunteers of age ranges 25-60 years old, once in rainy season in 2013. A molecular method targeted on an envelope gene was used to verify the dengue infection. During the study period, the dengue prevalence was highest in monsoon period and significantly declined in the winter and dry season. Infection rates in the vector of rainy, winter, dry of 2012 were 64.29%, 4.19%, 4.35% respectively and 8.70% in early rainy period of 2013. Various types (single- and multiple-) of infection within individual mosquito were positively associated with the increase of morbidity. Mean diversity and the evolutionary distance (p-distance) varied within all dengue serotypes by season. Considering to the biased-codon usage in the vector, only serotype-2 had varied by season. There is 9.62% of the rate found in plasma samples with the serotype-1, 3 and 4, which also showed various types of the infection. Host-specific mutation residues were mainly found in fusion loops in domain-III residues (serotype-1 and 2) of the envelope gene but only B-strand was found the mutation in serotype-3 and 4. All data revealed that the viral character considered in the structure of quasispecies. This data is significant for predicting further dengue situation for further surveillance and planning in order to eliminate the virus with effectively specific vaccination.
