Detection of pathogenic Leptospira spp. in peridomestic Rattus norvegicus in Hong Kong

Leptospirosis is a zoonotic bacterial disease that has a global impact on human and animal health. Rats are known as natural reservoirs of pathogenic <i>Leptospira</i> species. In the Hong Kong Special Administrative Region (SAR), the infection status of peridomestic rat species is not known. In this study, 250 rats belonging to four species (<i>Rattus norvegicus</i>, <i>R. tanezumi</i>, <i>R. andamanensis</i>, and <i>Niviventer huang</i>) were sampled from different ecological habitats across Hong Kong SAR in 2019, 2020, and 2022. The DNA extracted from the kidney tissues of the rats were screened using a polymerase chain reaction (PCR) for the pathogen-specific leptospiral gene <i>lipL32</i>. The positive samples were then confirmed by PCR targeting the <i>lfb-1</i> gene and were further sequenced for species group (SG) identification. The prevalence of pathogenic <i>Leptospira</i> in rats was 2.8 % (95 % confidence interval (CI) 1.23-5.93). Sequencing of the <i>lipL32</i> and <i>lfb-1</i> genes revealed two pathogenic species in seven <i>R. norvegicus</i> including <i>Leptospira interrogans</i> (belonging to <i>lfb-1</i> SG 8 and a novel SG) and <i>L.</i> <i>borgpetersenii</i> (belonging to <i>lfb-1</i> SG1)<i>.</i> Of the seven positive brown rats, five were caught from streets and within food stores in densely populated districts of Sham Shui Po and Kowloon City and the other two were trapped inside a chicken farm located in Yuen Long District. The results of this study demonstrate molecular evidence of pathogenic <i>Leptospira</i> spp. in the most common peridomestic rat species in Hong Kong SAR and highlight their potential role as a source of leptospirosis for humans and animals. The transmission of leptospirosis between humans, animals, and the contaminated environment emphasizes the necessity of addressing this disease through the One Health approach. Regular surveillance of <i>Leptospira</i> spp. in peridomestic rats, combined with and rat population control and environmental hygiene measures are essential to reduce the risk of <i>Leptospira</i> transmission from rats to domestic animals and humans.