Canine Leptospirosis - NYC Health

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Canine Leptospirosis

This information is intended for veterinarians to help inform conversations with pet owners on leptospirosis. Animal health providers may refer pet owners to the leptospirosis webpage. Additional languages are available at the bottom of this page.

Leptospirosis is a zoonotic disease that affects humans, dogs and other mammals. It is caused by bacteria that are shed in the urine of infected animals. Different strains of the bacteria have adapted to different animal hosts. In New York City, rats are the main source of canine and human infections. The best way to prevent leptospirosis is to avoid contact with rats and areas contaminated with rat urine, such as puddles.

Generally, dogs that develop acute illness with leptospirosis are incidental hosts. Transmission from incidental hosts to humans or other animals is rare.
Commonly reported signs of illness and complications identified among NYC dogs include:

Anorexia

Vomiting

Lethargy

Icterus

Renal failure

Liver failure

Veterinarians and veterinary diagnostic laboratories are required to report animals with a positive Leptospira test to the NYC Health Department.

For details about surveillance data and findings, refer to the 2023 Veterinary Advisory #11: 2022 Summary of Canine Leptospirosis Surveillance (PDF) in New York City.

Cases in NYC

The NYC Health Department investigates reports to gather data used to describe the characteristics of dogs diagnosed with canine leptospirosis and identify risk factors in the city. Dogs with leptospirosis have been detected in all five boroughs since reporting began in 2006. The map below shows where dogs with leptospirosis have been reported by the owners’ ZIP code. The number of dogs each year can be found by hovering over a blue-colored ZIP code.

The absence of cases in a ZIP code does not mean canine leptospirosis does not occur and may reflect owners’ ability to access veterinary care or lack of reporting. The veterinary community can use this map to know when and where canine leptospirosis has been reported in their area.

The chart below shows the number of reported dogs with leptospirosis by year. There has been a small increase in the number of cases since canine leptospirosis surveillance began in 2006. In 2023, the NYC Health Department started receiving reports from a second veterinary diagnostic laboratory causing an increase in the number of cases seen per year.

The chart below shows the cumulative number of reported dogs with leptospirosis by month. Cases are most often reported in late summer and early fall months.

Additional Resources

Print copies of the below can be ordered by calling 311.

Canine Leptospirosis Fact Sheet for NYC Veterinarians (PDF)

Leptospirosis Fact Sheet for Dog Owners (PDF)

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Leptospirosis

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Zoonotic and Vector-borne Diseases