Lymphatic filariasis (LF) is widely distributed in tropical and subtropical countries and targeted by the WHO for elimination as a public health problem by the year 2020. About 128 million people living in 78 endemic countries are infected with LF, primarily by W. bancrofti and to a lesser extent, by B. malayi and B. timori. Of the three physiological races of W. bancrofti, nocturnally periodic and the diurnally subperiodic physiological races are prevalent in India. While the nocturnal form transmitted by Cx. quinquefasciatus is prevalent in other parts of India, the diurnal form is prevalent only in the Nicobar group of Andaman and Nicobar Islands. Research on diurnally subperiodic form of filariasis commenced from the early forties, in the form of point prevalence studies which culminated in implicating Ochlerotatus niveus (=Downsiomyia nivea) in 1995. However there has been no comprehensive study on the clinical epidemiology and transmission dynamics of this form of filariasis. This monograph/book fills this gap.