LEPTOSPIRA IN DOGS IN HONG KONG: SEROLOGY AND URINARY SHEDDING

Leptospira interrogans causes leptospirosis in dogs and is a zoonotic infection. Vaccination is effective but protection is limited to specific serogroups. This study aimed to determine the prevalence and distribution of Leptospira serogroups and prevalence of urinary shedding in dogs in Hong Kong.
Microagglutination testing (MAT) of 22 serogroups was performed on residual diagnostic sera from 284 owned dogs. Titres above 1:100 were considered positive. Urine from 164 dogs undergoing neutering was tested for pathogenic leptospire DNA by LipL32 quantitative polymerase chain reaction (qPCR). Potential risk factors assessed included signalment, alanine transferase, alkaline phosphatase, bilirubin and creatinine. 
Overall seroprevalence was 9.86% (28/284) and 2.38% of tested dogs (5/210) had leptospiruria (median load 9.30 copies/ng of DNA [range 0.34–232], with a median Ct value of 36.36 [range 30.33–37.00]). In total, 53 positive antibody titres were obtained from 28 seropositive dogs, with 35.71% (10/28) seropositive dogs reactive to >1 serogroup (range 2–6). Fourteen distinct serogroups were detected at titres up to 1:3200, most frequently Pyrogenes (16.98%, 9/53), Copenhageni (13.21%, 7/53), Autumnalis (11.32%, 6/53), Cynopteri (11.32%, 6/53) and Ballum (11.32%, 6/53). Antibodies against vaccination serogroups Canicola (5.66%, 3/53), Pomona (3.77%, 2/53) and Grippotyphosa (3.77%, 2/53) were also detected.
Dogs in Hong Kong are exposed to a wide range of Leptospira serogroups. Current Leptospira vaccines are unlikely protect against the most prevalent serogroups. While prevalence of urinary shedding from dogs is low, gloves should be worn to handle canine urine to prevent zoonotic transmission. 
© 2023 The Authors. Journal of Veterinary Internal Medicine published by Wiley Periodicals LLC on behalf of the American College of Veterinary Internal Medicine.