Epidemiological screening and xenomonitoring for human lymphatic filariasis infection in select districts in the states of Maharashtra and Karnataka, India.

Lymphatic filariasis (LF) is a mosquito-transmitted tropical neglected parasitic infection that currently affects over 120 million people around the world and another 856 million people are at risk of acquiring the infection. Mass Drug Administration (MDA) spearheaded by the World Health Organization is the only current strategy to control this infection in endemic areas. In this study, we performed an epidemiological survey in select regions in the southern parts of India to determine the current status of LF infection in subjects. Night blood samples were collected from 916 subjects after proper consent and were screened for the presence of circulating microfilariae of Wuchereria bancrofti in their peripheral blood. Our results showed the presence of 51 (5.56%) cases of human LF infection in the surveyed areas including new cases for LF, which were not recorded previously. Given the presence of new cases of LF infections, we trapped mosquitoes from these regions and screened for the presence of W. bancrofti L3 specific Ssp1 DNA repeat sequences by PCR. Our results confirmed the presence of LF infection in the mosquitoes collected from six out of nine districts that we surveyed. These findings confirm active transmission of LF infection in all of the areas that we surveyed, despite several years of MDA treatment. The findings in this study suggest potential reemergence of LF infection in most of the areas we surveyed and warrants for a more stringent strategy for controlling LF in these endemic areas.