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

Pathogenic species of the genus Leptospira cause an underdiagnosed zoonosis in humans and animals called leptospirosis. Animal reservoirs often remain asymptomatic yet shed the active spirochete in urine, making the control of leptospirosis transmission to humans more challenging. Asymptomatic leptospirosis in human companions, such as dogs and cats, resulting in unrecognised infections, has been demonstrated in a few countries. Crucially, the current lack of molecular epidemiology data on Leptospira among companion animals in Thailand underscores the urgent need to investigate transmission dynamics for effective regional control. We investigated the prevalence of Leptospira infection in cats and dogs during neutering in seven provinces across Thailand. The urine samples were screened for Leptospira DNA by PCR targeting the rrs gene and further speciation using the Sanger Sequencing Analysis. The 56/567 (9.9%) animals were positive for Leptospira in the Pathogen clade, including 34/303 (11.2%) dogs and 22/264 (8.3%) cats. The partial rrs gene analysis identified L. interrogans, L. weilii, and L. borgpetersenii (4.4%) as well as Pathogen subclade 2 species (1.4%). Notably, this study reports the first molecular detection of L. yasudae (1.0%) in companion animals in Thailand. The identification of these three key pathogenic Leptospira species, common causes of human leptospirosis in Southeast Asia, in clinically healthy owned and free-roaming dogs and cats, suggests the risk of human leptospirosis in the areas investigated. These companion animals, often living in close contact with human, may contribute to daily risks. Therefore, enhanced surveillance and vaccination programs for dogs and cats, coupled with targeted public awareness campaigns, are critical for mitigating the risk of human infections.