Potential Zoonotic Infections Transmitted by Free-Ranging Macaques in Human–Monkey Conflict Areas in Thailand

Abstract

Introduction: Nonhuman primates (NHPs) can transmit zoonotic diseases to humans because of their close genetic relationship, facilitating the cross-species transmission of certain pathogens. In Thailand, Macaca is the most common NHP genus and their inhabits area are in close proximity of human, particularly in urban and suburban areas, where frequent interactions with humans increase the risk of pathogen transmission. The risk is influenced by factors such as the type of pathogen, the mode of transmission (e.g. direct contact or vector-borne), and the density of human and macaque populations in the regions. This study aims to investigate potential zoonotic infections in free-ranging macaques residing in human–monkey conflict areas. Methods: From 2014 to 2023, 2703 macaques across 29 provinces in Thailand were tested for 18 pathogens using PCR, RT-PCR, or real-time PCR. The associations between disease occurrence, demographic variables, and sample types of macaques were analysed using univariable and multivariable regression. Results: The overall pathogen infection percentage was 35.7% (965/2703). Simian foamy virus (SFV) had the highest infection percentage at 52.5% (759/1446), followed by Herpesviridae at 41.4% (353/852), Plasmodium spp. at 1.8% (14/758), and hepatitis B virus at 0.1% (2/1403). Significant differences were observed among different sampling sites, macaque age groups, and species in infection proportion of SFV, and Herpesviridae. Conclusions: Identifying the pathogens carried by macaques is crucial for preparing for potential disease epidemics and outbreaks.