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Urinary Shedding: The Real Hidden Risk of Leptospirosis Transmission

Natalie L. Marks, DVM, CVJ

Infectious Disease


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Urinary Shedding: The Real Hidden Risk of Leptospirosis Transmission
Sponsored by Merck Animal Health

Leptospirosis is the most common infectious zoonotic disease worldwide and is considered to be a re-emerging disease and significant threat to canine health in all regions of the United States.1 Although veterinarians are commonly educated on the acute presentations of canine leptospirosis (eg, inappetence, vomiting, fever, lethargy), many may not be aware of the chronic carrier state that can produce idiopathic polyuria/polydipsia or result in no clinical signs at all.1 These chronic carriers pose a risk to humans in their household, veterinary teams, and other dogs in the community.2

Prevention of disease is best achieved through an understanding of how a patient becomes infected and the pathophysiology of the organism. Direct transmission of Leptospira spp occurs when dogs come in contact with infected urine or ingest infected tissue. Once infection ensues, the spirochetes travel the bloodstream for several days, creating leptospiremia; after this phase, they can infect and set up residence in other organs, including the kidneys.3 This can create a carrier state. Shedding of leptospires in the urine (ie, leptospiruria) can persist for ≤3 months if there is inappropriate or absence of appropriate treatment.4

The significance of the chronic carrier state in the canine population could easily be underestimated, since these dogs may show no clinical signs of disease. In one study, PCR testing demonstrated that 8% of dog from a group of 500 seen at a veterinary teaching hospital excreted leptospires in the urine.5 Only 10% of the shedding dogs had clinical signs of leptospirosis.

In one study, PCR testing demonstrated that 8% of dog from a group of 500 seen at a veterinary teaching hospital excreted leptospires in the urine.

These chronic carriers pose a substantial hidden risk for transmission within homes, dog parks, kennels, and daycares. In our role as public health officers, it is imperative to choose a vaccine that prevents not only mortality but also leptospiremia and subsequent leptospiruria and urinary shedding. At the 2016 International Society for Companion Animal Infectious Diseases meeting, researchers presented a set of challenge studies that were conducted using 2 groups of puppies: those appropriately vaccinated as compared with a placebo group and then challenged. Urine samples were evaluated over 35 days and blood samples over 10 days. Results indicated no evidence of leptospiremia or leptospiruria in any of the vaccinated puppies, firmly supporting the claim of prevention of urinary shedding.6 Choosing this vaccination strategy provides the best chance for protection for patients, pet parents, and veterinary team members.


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