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

## TL;DR

This study finds that nearly 10% of neutered dogs and cats in Thailand carry pathogenic Leptospira, highlighting a risk of human leptospirosis from companion animals.

## Contribution

The first molecular detection of Leptospira yasudae in companion animals in Thailand is reported.

## Key findings

- Nearly 10% of asymptomatic dogs and cats tested positive for pathogenic Leptospira.
- L. yasudae was detected for the first time in animal urine samples in Thailand.
- Three Leptospira species known to cause human disease were identified in clinically healthy pets.

## Abstract

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.

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.