ABSTRACT
Dengue, a vector-borne disease remains as one of the most serious public health problems globally. Incidence of this disease is on an increasing trend and currently over a billion people in tropical and subtropical regions are at risk. In the absence of an operational vaccine, prevention of dengue virus (DENV) is primarily focused upon controlling mosquito vectors. Mosquito vector surveillance programmes require simple and rapid tools to detect mosquitoes infected with DENV. Here, we tested the commercially available DENV Detect™ NS1 ELISA kit (InBios International, Inc.) for detection of recombinant DENV-NS1 protein in Aedes mosquito samples. The kit was evaluated to find out the minimum detection limit of recombinant DENV-2 NS1 protein following the manufacturer’s instructions. Initially, the NS1 protein detection threshold of the kit was determined and later the assay was standardized for detection of NS1 protein in Aedes aegypti mosquito pools containing 5, 10 and 25 mosquitoes. The ELISA kit displayed high sensitivity towards detection of recombinant dengue virus-2 NS1 protein in mosquito pools (up to 25 mosquitoes per pool) at 25 pico gram concentration. Since the commercial NS1 ELISA is highly sensitive and follows a very simple procedure, it could be employed for DENV surveillance in Aedes aegypti mosquitoes, after carrying out laboratory and field bioassays with DENV infected specimens.
ABSTRACT
An unprecedented outbreak of dengue occurred during 2017 in Kerala. Thiruvananthapuram was worst affected. We carried out a joint investigation with the Health department of the State, to understand the epidemiological and entomological factors involved in this outbreak, so as to develop strategies to contain it. Blood samples from suspected patients were collected from three worst affected areas and genomic analysis of the Dengue virus (DENV) was performed. Also, a cross sectional entomological survey was carried out in these areas. The data obtained was compared with the available secondary data of DENV in Kerala. The investigations revealed a genetic shift from the erstwhile predominant DENV2/DENV3 serotypes to the newly introduced DENV1 Asian genotype during the current outbreak. Breeding indices of Aedes aegypti, the predominant vector species was also found to be remarkably high. Asian genotype of DENV1 was detected in field collected Ae. aegypti also. The index cases of the Asian genotype of DENV1 in Kerala were detected from Erumeli village (gateway to the famous Sabarimala shrine) among two plantation workers migrated from the neighbouring Karnataka state, during 2013. This introduced virus strain attained an epidemic proportion in 2017 in Thiruvananthapuram, owing to immunologically naïve population and high receptivity.