Integrated One Health Surveillance of Zoonotic Diseases at the Wildlife-Human Interface: How Pathogen Detection Informs Spillover Risks and Transmission Dynamics

Emerging infectious diseases (EIDs) pose a significant global health challenge, with zoonotic pathogens-- transmitted from animals to humans--accounting for about 75% of these threats. Traditionally, responses to EIDs have been reactive, focusing on post-outbreak containment, which often results in considerable health and economic losses. Recognizing the need for a proactive One Health approach, our study in the buffer zone (Thakurdwara) of Bardia National Park, Nepal aimed to establish a zoonotic disease surveillance program. We conducted disease risk assessments and collected biological samples from 100 households located in the wildlife-human interface of the park. This included one human sample (n=100) and at least two livestock samples per household (n=289). Fecal samples from the surrounding forest were non-invasively collected and identified using DNA barcoding. All samples were screened for ten target pathogens, including six viruses and four bacteria, using polymerase chain reaction (PCR) and DNA sequencing. By integrating laboratory findings with risk survey data using a One Health approach, we analyzed potential zoonotic pathogen spillover and transmission dynamics to better understand the interconnected factors influencing zoonotic disease risks. Campylobacter emerged as the most common pathogen, detected in 97 human households and 219 livestock samples. Mycobacteria were identified in two livestock and two wildlife samples, while Salmonella was confined to a single human household. Influenza A virus was observed in one livestock sample, and wildlife samples showed low pathogen prevalence overall. Campylobacter hotspots were identified through strain variation and network analysis, linking humans, livestock, and poultry, based on proximity, shared water sources, and contamination. Poultry likely served as a reservoir for human cases indicating zoonotic transmission pathways. Our findings highlight the critical need for integrated One Health measures and proactive, integrated surveillance systems that emphasize early detection, community education, and targeted interventions to mitigate emerging zoonotic threats.