Genetic characterization and molecular phylogeny of Aedes albopictus (Skuse) species from Sonitpur district of Assam, India based on COI and ITS1 genes.

BACKGROUND & OBJECTIVES: Aedes albopictus (Skuse) is one of the major vectors of dengue which is an emerging threat in Northeast part of India. The morphological characterisation of mosquitoes is time consuming and lacks accuracy for distinguishing closely related species. Hence, molecular methods of mosquito identification, genetic diversity and molecular phylogeny have gained increased importance. This study was aimed to identify and characterize the most abundant species of Aedes vectors collected from different breeding spots in Assam, Northeast India employing molecular as well as bioinformatics tools.

METHODS: Ae. albopictus species was genetically characterized with internal transcribed spacer1 (ITS1) and cytochrome c oxidase subunit I (COI) genes and sequence analysis was carried out following molecular methods like PCR amplification, DNA sequencing and multiple sequence analysis. Maximum likelihood molecular phylogeny was reconstructed to define the evolutionary relationship among studied isolates and isolates from other parts of Southeast Asia.

RESULTS: Molecular study revealed that all five subject specimens belonged to Ae. albopictus species as per both ITS1 and COI genes. Maximum likelihood tree based on ITS1 and COI genes showed that isolates were distinctly grouped into separate clusters. Almost similar pattern of amino acid frequencies in COI gene was found amongst the five studied isolates. However, amino acid frequency in ITS1 gene was found to be dissimilar, indicating polymorphisms in this gene, among the isolates.

INTERPRETATION & CONCLUSION: This is the first report among the Northeastern states of India describing the genetic make-up of Ae. albopictus species by virtue of highly conserved mitochondrial (mt) DNA and ribosomal (r) DNA gene sequences. This study also illustrates that the sequence diversity of these two genes in this mosquito species differs geographically which differentiate a population and brings unique identity.