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Veterinary Alert: Leptospirosis Outbreak in Dogs in Maricopa County

Thursday, November 10, 2016  
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Some Maricopa County veterinarians are seeing an increase in the number of cases of canine leptospirosis.  At least 20 laboratory positive dogs have been reported since the beginning of the year. Most of the cases have been associated with two clusters including one reported in February involving show dogs and a more recent one involving a boarding facility. Clinical presentations have ranged from asymptomatic infections and conjunctivitis to kidney failure. Until recently, canine leptospirosis cases in Arizona were considered to be rare and sporadic and had not occurred in outbreak settings. 


Leptospirosis is caused by any one of >250 Leptospira interrogans serovars and is transmitted through direct contact with urine, water, soil, or contaminated fomites. The bacteria can survive in water or moist soil for weeks to months, and persistently infected dogs can shed the bacteria in urine for months to years. Infection can be asymptomatic or severe, and range from acute to chronic infection. Signs and symptoms in dogs include fever and depression, as well as kidney involvement with polydipsia (excessive thirst and fluid intake), polyuria (increase urine output), oliguria (decreased urine output), or anuria (no urine output).  Liver failure is also common with some serovars. Veterinarians should consider ordering leptospirosis testing for dogs presenting with compatible symptoms. For more information on leptospirosis diagnosis and treatment, go to:


While the serovars that are often diagnosed in dogs (e.g.  Canicola, Grippotyphosa, Pomona, etc.) rarely cause illness in humans, people in close contact with infected pets are at risk.  Prevention precautions should be taken by veterinary staff and pet owners to reduce transmission risk. This includes:

  • using personal protective equipment (PPE) when handling infected animals
  •  routine disinfection of urine contaminated areas, and
  • proper disposal of potentially infectious bodily fluids


In humans, leptospirosis infection can cause a wide spectrum of illness ranging from asymptomatic or mild disease to kidney failure, aseptic meningitis, or other severe life-threatening syndromes.


In light of recent trends, veterinarians might want to recommend leptospirosis vaccination for dogs that may be at increased risk for exposure (see below).  Choose a vaccine that provides protection against Serovars   Canicola, Grippotyphosa, and Pomona. 


Dogs at increased risk may include:

  • Outdoor dogs that engage in hiking, wading, and swimming in natural waters

  • Dogs on ranches and farms where there is contact with other animals and animal urine

  • Hunting dogs

  • Dogs that are frequently exposed to areas of flooding

  • Dogs that reside in rural areas or fringe areas where there is potential contact to wildlife or animal urine

  • Dogs that have frequent exposure to other dogs and dog urine such as at dog shows, dog parks, pet boarding facilities, etc.

  • Dogs that travel widely and have contact with other dogs and/or other animals


Veterinarians should be aware that vaccine reactions (including anaphylaxis), though uncommon, have been linked to the Leptospira vaccine. Veterinarians and owners should watch vaccinated animals for 24 hours following vaccine and note any adverse effects – including swelling and redness at the vaccine site, lameness in the leg proximal to the vaccination site, or depressed appetite. If owners are concerned about an adverse reaction, it is possible to pre-treat with diphenhydramine.


Leptospirosis is a reportable disease in Arizona, and veterinarians are encouraged to report probable or confirmed leptospirosis cases to the Arizona Department of Agriculture or the Arizona Department of Health Services ( For more information about disease reporting, please visit

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