Ha Thi Thanh Nguyen: Zoonotic risks in wildlife farming systems in Vietnam: An assessment using a One Health approach

Abstract

Zoonoses originating from wildlife pose increasing threats to global health, particularly in biodiversity-rich regions like Southeast Asia. In Vietnam, wildlife farming is a growing economic sector, yet its role in facilitating interspecies transmission of zoonotic pathogens remains underexplored. This PhD project applied a One Health approach to assess zoonotic transmission risks in wildlife farming systems in Vietnam to inform risk-based surveillance and targeted prevention strategies. The thesis comprises the following studies: (1) a systematic review of zoonotic pathogens from wildlife in Southeast Asia; (2) field studies in two provinces in Vietnam, including an assessment of wildlife farmers’ knowledge, attitudes, and practices (KAP); serological testing and risk factor analyses among farmers; molecular detection of coronavirus (CoV), hantavirus and hepatitis E virus (HEV) in wildlife and human samples; and (3) a qualitative risk assessment of transmission at the high-risk node along the wildlife supply chain. Findings from 108 reviewed publications highlight diverse zoonotic pathogens from wildlife in Southeast Asia, with transmission driven by interconnected environmental, animal, human, and human-animal-environment interface factors. Among 210 wildlife farmers, KAP results showed high knowledge scores (mean 10.1/13), positive attitudes (41.3/50), but moderate preventive practice (14.1/30). Qualitative findings revealed a gap between farmers’ knowledge and practices, driven by low-risk perception, mistrust of authorities, and concerns about reporting consequences. Serological analysis identified 8.7% hantavirus IgG, 1.9% IgM, and 26.7% HEV IgG among farmers. Risk factor analyses showed that hantavirus exposure was associated with exclusive wildlife farming (OR = 2.7; 95% CI: 1.1 – 6.9), while HEV exposure was linked to male gender (OR = 3.1; 95% CI: 1.4 – 7.3), raw wild meat consumption (OR = 6.8; 95% CI: 1.6 – 31.8), and reported use of protective clothing (OR = 4.0, 95% CI: 1.4 – 11.2), however the correctness of its use were not evaluated. Molecular testing detected diverse CoVs and HEV in both wildlife and human samples, including porcine, bat, avian CoVs, SARS-CoV-2 from wildlife samples; HCoV-HKU1, -OC43, SARS-CoV-2 from human samples, and HEV genotypes 3 and 4 in wild boar faeces, with some detected on the same farms. Higher practice scores were associated with lower PCR positivity (OR = 0.9; 95% CI: 0.8 – 0.99). Risk assessment identified wildlife farms as the highest-risk node due to frequent human-wildlife contact, high density, poor biosecurity, and mixed-species rearing. Specifically, at the farm level, CoV posed a low risk to animals and low-to-high risk to humans, hantavirus posed a low risk to both animals and humans, and HEV posed a low risk to animals but medium risk to humans. Overall, this thesis provides evidence and insights to inform zoonotic disease prevention and supports operationalizing One Health strategies to reduce zoonotic transmission risks in wildlife farming settings.