The Centers for Disease Control removed Leptospirosis from the “reportable human diseases” list, but there is still significant concern over this zoonotic disease.  Our pets are susceptible to lepto as well, but many owners are afraid to vaccinate for the illness.   What’s the real story and how can we keep our pets and families safe?

Mary Fleming always followed the advice of her veterinarian when it came to her miniature poodle, Mitsie.  Regular examinations, heartworm preventive and even a good diet helped keep Mitsie active and healthy.  Thinking that Mitsie was safe, Mary did not opt for a Leptospirosis vaccine for her dog.  Unfortunately, Mitsie got very sick not long after visiting her city’s dog park and needed intensive care and hospitalization.  Thankfully, her veterinarian was there to help her recover and explain how moist soil or puddles at the park actually put Mitsie at risk!

Leptospirosis is a zoonotic disease- a disease that can be passed between animals and people.  It is spread by spirochete (spiral-shaped) bacteria in the urine of infected rodents, wildlife, and pets.  There are more than 200 different strains of lepto and certain strains appear to prefer certain hosts, like dogs, pigs, raccoons or even rats.

The leptospira organisms enter the body through mucous membranes or through abrasions on the skin. People and animals can become infected from direct exposure to infected urine, but also through contaminated environment, such as water or damp soil. 

People and pets are also exposed to Lepto while camping or participating in outdoor recreational activities. Drinking or swimming in water that is infected with Lepto is the most common exposure, but wet soil can be contaminated as well.  And, as Mitsie’s case illustrates, a city environment will not always provide protection against this serious disease.

The signs of Leptospirosis can mimic many other diseases and illnesses.  The first signs in dogs are often depression, loss of appetite, vomiting, weakness, and generalized pain.  Affected dogs may also drink water and urinate excessively and have swollen, red, and painful eyes.  Because these signs are common to other diseases and non-specific, owners may try to treat their pets at home for such problems as an upset stomach or arthritis. 

This “wait and see” response delays proper diagnosis and treatment for the dog, as well as increasing the owner’s exposure to the disease.  If caught early, treatment is usually effective and the survival rate is good.  However, time is of the essence.  A mere three or four day delay can lead to irreversible kidney failure.

Vaccines are available but many pet owners, like Mary above, have either experienced or heard about adverse reactions associated with these vaccines.  In the past, Leptospirosis vaccines were generally created using the whole bacterial organism.  In many cases, when a whole bacterium is used, the likelihood of a “vaccine reaction” increases.  Thankfully, newer vaccines have been developed that reduce this possibility by using specific Leptospirosis proteins instead of the whole organism.

A study reviewing vaccine reactions in more than one million dogs vaccinated found that reactions occur about 13 times for every 10,000 vaccines given.  More importantly, the lepto vaccine was no more likely to cause a reaction than any other vaccine.

So, if the vaccine appears to be safe and the disease deadly, shouldn’t all dog owners vaccinate their pets?

Unfortunately, that question is difficult to fully answer.  Because there are so many Leptospirosis strains, no one vaccine will cover every possible exposure a pet might have.  At present, vaccines are available that protect against four of the common strains infecting dogs.  In addition, the vaccine will prevent clinical disease, but may not stop the pet from shedding bacteria in his urine.  This makes the pet a threat to other animals, especially those who are not vaccinated.  And, as mentioned above, humans are at risk as well.

Worldwide, Leptospirosis is the most widespread zoonotic disease.  Cases occur routinely in tropical countries, but increases have been seen in Europe and North America as well.  Floods and hurricanes are instrumental in spreading this illness and coordinated efforts to rescue and re-home pets from these disasters might actually transplant lepto into new areas.

Protecting your pet from Leptospirosis is a complex situation.  Use your veterinarian as a resource to help assess your pet’s risk factors as well as the benefits and hazards of vaccination.  We routinely vaccinate for leptospirosis in our hospital.  Other important steps that might minimize your pet’s exposure to this disease include removing animal pests, such as rodents and draining areas of standing water.   For more information, visit our Pet Health Library at