What is Leptospirosis?

lepto photoLeptospirosis is a potentially zoonotic bacterial disease, defined as a disease spread from animals to people.  Most human cases occur from wildlife sources such as raccoons, squirrels, foxes, skunks, opossums, coyotes and rats whose urine has contaminated standing water or soil.  Direct transmission from pets to people is uncommon but has been reported, usually from pet rats.  The bacteria penetrates mucous membranes or abraded skin.

 How is Leptospirosis Transmitted?

Disease in dogs is also caused by coming in contact with water contaminated by urine from wildlife reservoir hosts.  It is most common in areas with higher rainfalls and a warm climate.  In the US, it is found most commonly in Hawaii, the Midwest, along the West Coast and in the Northeast.  There is a seasonal peak incidence in late Fall, possibly because of increased wildlife migration and more urine marking.

 What are the Symptoms of Leptospirosis?

The incubation period in dogs, or the time between being exposed to the bacteria and the time of showing symptoms has been shown to be 7 days in experimental studies.  Symptoms can be mild and include vague lethargy and inappetance.  Or they can be severe with life threatening kidney and liver failure.  Symptoms in the more severe cases include vomiting, diarrhea, severe lethargy, increased thirst and urination, and jaundice.

How is it Diagnosed and Treated?

Leptospirosis is diagnosed with a blood test.  It can sometimes be negative in the first week of illness and therefore the blood test should usually be repeated 2-4 weeks later.  Supportive care for the severe cases requires hospitalization for intravenous fluid therapy and monitoring of bloodwork and urine output.  Treatment of the actual infection requires antibiotics.  Doxycycline given orally for 2 weeks is recommended if the patient can hold oral medications down.  Injectable Ampicillin or Penicillin G should be given initially if vomiting precludes oral medications.  The dog’s urine will no longer be a source of infection within 48-72 hours after starting appropriate antibiotics.  When treated early in the disease, the kidneys can return to normal.  When treated later, permanent kidney damage can occur.  Dialysis can be a life-saving therapy for even the most severely affected dogs.jenna zimmerman


In experimental challenge, the current “4 serovar” Leptospirosis vaccines appear to be effective in preventing disease and also in preventing shedding of the bacteria in urine of exposed dogs.  These vaccines are protective for at least 12 months.

Despite the common conception that Leptospirosis vaccine may cause life threatening anaphylactic reactions especially in smaller breed dogs, actual evidence to support this does not exist.  In a study of acute vaccine reactions in dogs utilizing a large database, vaccines containing Leptospirosis were no more reactive than other vaccines.

Annual vaccination is recommended in geographic areas where infection occurs in urban and backyard dogs (this includes the Northeast).  Decreasing access to marshy areas and standing water and minimizing wild animal contact by the use of fencing and rodent control is also recommended.  Whether life-long immunity occurs after natural infection is unknown, therefore even dogs that have recovered from Leptospirosis should be vaccinated annually.