High burden and spatial clustering of canine hemoparasitic infections in southern Thailand: A molecular survey of free-roaming dogs

Canine vector-borne pathogens (CVBPs) are increasingly prevalent in tropical and subtropical regions, particularly among free-roaming dog populations, which serve as key reservoirs for transmission. This study investigated the prevalence and the spatial distribution of CVB pathogens in 318 free-roaming dogs from five sub-districts of Songkhla Province, southern Thailand. Conventional PCR was utilized to detect eight pathogens: Anaplasma platys , Ehrlichia canis , hemotropic Mycoplasma spp., Babesia spp., Hepatozoon spp., Trypanosoma evansi , Dirofilaria immitis , and Brugia malayi . An overall infection rate of 77.04% was observed, with A. platys (51.89%) and hemotropic Mycoplasma spp. (27.04%) being the most prevalent. Co-infections were common, occurring in over 42% of infected dogs. Spatial analysis using kernel density estimation (KDE) revealed pathogen-specific clustering patterns, particularly in the central and southwestern areas of the province. Infection prevalence was significantly associated with host factors such as age and weight. These findings highlight the critical role of free-roaming dogs in the epidemiology of CVBPs and the need for targeted surveillance and vector control strategies to mitigate zoonotic transmission. This One Health integrative approach provides a comprehensive assessment of pathogen diversity and prevalence while identifying environmental and host-related factors that may influence their geographic distribution. • High prevalence (77%) of blood-borne parasites was detected in free-roaming dogs in southern Thailand. • Co-infections were common (42%), including cases with two, three, or four pathogens simultaneously. • Results highlight the role of free-roaming dogs as reservoirs and emphasize the importance of integrated One Health approaches for disease control.