Pathogenic Leptospira species identified in dogs and cats during neutering in Thailand

Abstract Pathogenic species of Genus Leptospira cause an underdiagnosed zoonosis in humans and animals called leptospirosis. Animal reservoirs getting infections without signs can carry and shed the active spirochete into the environment through their urine, making the control of leptospirosis transmission to humans more challenging. Asymptomatic leptospirosis in human companions, such as dogs and cats, leading to unawareness of infections, has been demonstrated in a few countries. Monitoring disease prevalence and investigating molecular epidemiology is essential for controlling and preventing human and animal leptospirosis transmission. To investigate the prevalence of Leptospira infection among cats and dogs in Thailand, we collected 567 urine samples through a neutering program in seven provinces across the central, western and southern regions. The urine samples were screened for Leptospira ’s DNA and further speciation using the Sanger Sequencing Analysis. 34/303 (11.2%) dogs and 22/264 (8.3%) cats tested positive for Leptospira in the Pathogen clade. The partial rrs gene analysis identified L. interrogans , L. weilii , and L. borgpetersenii (4.4%). We first reported L. yasudae (1.0%) and other new species of the Pathogen subclade 2 (1.4%) infections among these dogs and cats. Three key pathogenic Leptospira species commonly causing human leptospirosis in Southeast Asia were identified in healthy owned and free-roaming dogs and cats, suggesting the risk of human leptospirosis in the areas. These animal reservoirs (probably living under the same roof as us) can transmit diseases daily to owners (caretakers), other animals and the environment. Effective public awareness campaigns on the transmission might encourage dog and cat health surveillance and vaccinations, reducing human infection risks. Author Summary Leptospirosis, a neglected zoonotic disease caused by pathogenic species of genus Leptospira , can be transmitted to humans through contact with infected animal body fluids or contaminated environments. Free-ranging dogs and cats can shed infectious Leptospira in their urine, posing a significant risk. In Thailand, animal vaccine coverage for diseases like leptospirosis in these animals is unknown and unregulated, raising concerns about zoonotic transmission and reflecting a lack of routine veterinary support. Our study joined non-profit, volunteer-led neutering programs that travel to various provinces, offering free services for owned and unowned pets. This allowed our team to collect urine specimens directly from the urinary bladder for the detection of Leptospira . We found nearly 10% of the recruited asymptomatic dogs and cats were infected by the molecular screening assay. Three pathogenic Leptospira species, commonly infecting humans globally, were identified. Notably, we report the first detection of L. yasudae in animal urine samples, providing evidence of infectivity for a species not previously recognised for its pathogenicity and typically reported from the environment. This highlights the risk of human leptospirosis from contact with cats and dogs, emphasising the need for public awareness and annual vaccination programs for all pets.