PROJECT SUMMARY Soil transmitted helminths (STH) - hookworms (Ancylostoma duodenale and Necator americanus), Ascaris lumbricoides and Trichuris trichiura - are among the most widespread neglected tropical diseases (NTD) of humans worldwide, disproportionately affecting the poorest and most vulnerable communities. In rural, populations, intensive animal-human mixing with livestock and companion animals combined with poor hygiene and sanitation can lead to transmission of zoonotic infections as well as result in zoonotic sources of infection. It is estimated that 30% of households globally have domestic livestock animals, with south and southeast Asia and Africa contributing the largest proportion. These regions also have the highest burden of STH globally. Most epidemiological surveys and mathematical models of STH do not account for or measure the risk of infections acquired from zoonotic sources, either by direct contact with animals or animal feces or indirectly from the environment. The inability to interrupt transmission due to presence of zoonotic and environmental reservoirs of infection may prolong mass drug administration (MDA) campaigns and result in emergence of anthelmintic resistance. The overarching goal of this multi-disciplinary collaborative application is to use a One Health framework to examine the interconnected burden and transmission patterns between human, animal and environmental reservoirs of STH by integrating carefully collected epidemiological, environmental and qualitative research data with state-of-art molecular techniques to better inform monitoring and elimination strategies in endemic communities. We will leverage an ongoing randomized controlled trial on community wide MDA and an upcoming One Health project in two eco-epidemiologically and culturally distinct geographic regions of India (Tamil Nadu and Meghalaya) to: (1) comprehensively investigate the transmission dynamics of different STH species at individual, household and com