Rats, Your Dog, Your Family, and Leptospirosis

by Linda L.


There are many reasons to brag about this amazing city that we call home – the food, the museums, that skyline, those beaches, the sports teams (OK…at least some of them), the layout (YAY grid system), our diversity, and our culture.  With all Chicago has going for it, we also hold the unfortunate title of being America’s rattiest city. That’s right.  Last fall, Orkin bestowed this title on Chicago for the third time running.

If this is old news, why are we talking about it?  As the weather has warmed up, chances are you and your two-legged and four-legged family members are spending more time outside. Those rats (and other rodents and mammals) will also be out and about enjoying the various bounties the city has to offer them.  We wanted to remind you of one of the dangers for your pets AND the two-legged members of your family in this rattiest city in America – leptospirosis.

What is leptospirosis?

Leptospirosis is a zoonotic (can be spread from animals to humans) disease that is caused by infection with the Leptospira bacteria.

Why are we talking about leptospirosis and rats?

Instances of leptospirosis in dogs have been on the rise, as have the complaints about rats in Chicago.  Leptospirosis is typically contracted by drinking or absorbing, through mucus membranes (eyes, nose, mouth, or cuts/abrasions in the skin), water that has been contaminated by the urine of infected animals.  Infected wildlife, most notably rats in urban areas like Chicago, urinate in/near puddles, lakes, streams, or other areas with standing water and help spread the bacteria.

Common risk factors for leptospirosis:

  • Exposure to or drinking contaminated water from rivers, lakes or streams
  • Roaming on rural properties (exposure to infected wildlife, farm animals, or water sources)
  • Exposure to wild or farm animal species, even if in the backyard
  • Contact with rodents or other infected dogs, such as in urban areas, dog parks, or multi-dog facilities

Can people get leptospirosis?

According to the CDC website, cases of leptospirosis in children are on the rise in urban areas, although potential reasons for the trend were not listed.  The AVMA website states, “Most cases of human leptospirosis result from recreational activities involving water.  Infection resulting from contact with an infected pet is much less common, but it is possible.”

Can cats get leptospirosis?

According to the AVMA, dogs are most commonly affected.  “Leptospirosis in cats is rare and appears to be mild, although very little is known about the disease in this species.”

What are the symptoms of leptospirosis?

The signs and symptoms of leptospirosis in dogs can vary greatly based on the specific strain of bacteria as well as how the dog’s immune system reacts to the infections.  Some dogs may be asymptomatic while others will develop severe, life-threatening illness.

Signs of leptospirosis can vary and be similar to those of other illnesses.  We advise you to seek veterinary care for your dog if you observe the following symptoms:

  • Vomiting
  • Diarrhea
  • Dehydration
  • Lethargy
  • Loss of appetite
  • Jaundice
  • Fever
  • Shivering
  • Muscle tenderness and/or reluctance to move
  • Increased thirst
  • Changes in frequency or amount of urination


As with dogs, signs and symptoms of leptospirosis in humans can vary widely, but are often flu like – high fever, headache, chills, muscle aches, vomiting, abdominal pain, and diarrhea.  Symptoms usually appear 1-2 weeks after exposure.  In the majority of human cases of leptospirosis, there are minimal to no symptoms.  However, severe cases can lead to meningitis or encephalitis, as well as Weil’s disease (kidney and liver failure, pulmonary hemorrhage).  It is important to seek treatment in cases in pets or people, as recovery will be greatly prolonged without it.


How is leptospirosis diagnosed?

In order to reach a diagnosis, the veterinarians at Family Pet Animal Hospital will consider various factors – your dog’s vaccination status, information from your pet’s history, likelihood of exposure, clinical symptoms, physical exam findings, along with routine and specialized laboratory tests.

Routine tests, including a complete blood count (CBC) and blood chemistry, may reveal typical clinical symptoms of leptospirosis infection – an elevation in a pet’s white blood cell count and/or changes in liver enzymes, thrombocytes, and kidney values (BUN and creatinine).  Because there are many diseases in dogs that will have identical clinical symptoms to those seen in cases of leptospirosis, you pet’s veterinarian may run more specialized tests such as a polymerase chain reaction (PCR) test or microscopic agglutination test (MAT), although each has its limitations.

The leptospirosis PCR test can detect the presence of Leptospira in your pet’s blood and/or urine, can be an effective diagnostic test during the early stages of infection and before antibiotics have been started, but under certain circumstances, can give false positives or negatives.  A “MAT” or microscopic agglutination test can detect the presence of antibodies against Leptospira in a dog’s blood but also has its limitations.  The time frame required to obtain results of the MAT test is longer than that of a PCR test and a follow-up test may be necessary confirm infection.  Additionally, if the pet received antibiotics recently or was previously vaccinated for leptospirosis, the MAT results can be inconclusive.

Due to the limitations of these specialized tests based on each individual pet’s circumstances and history, the zoonotic nature of the disease, and the fact that infection can be life threatening, our veterinarians will begin treatment for the patient if leptospirosis is suspected but not definitively confirmed via testing.  Delaying treatment could be highly detrimental to your pet’s health.

Treatment and prevention of leptospirosis

Treatment for leptospirosis generally involves hospitalization, antibiotics, and supportive care.  If treated early and aggressively, chances for recovery are good.  However, there is a risk of permanent kidney or liver damage.  If treatment is delayed or not sought, the disease can be fatal.

Vaccination is the best protection for your dog against leptospirosis.  There are 10 serovars (strains) of Leptospira and the current vaccine used by the veterinarians at Family Pet Animal Hospital protects against four serovars (the most coverage available).  V accinating your dog does not guarantee s/he will not contract leptospirosis, however it is the best defense available.  The veterinarians at Family Pet highly recommend vaccinating your dog against this serious and potentially deadly disease.

Due to the zoonotic potential and high mortality rate of leptospirosis, the American College of Veterinary Internal Medicine (ACVIM) strongly recommends leptospirosis vaccination for all dogs.

Because leptospirosis can be transmitted to humans, you must take precautions to protect yourself, your family, and the community if your dog is infected:

  • Follow your veterinarian’s instructions for treatment of your dog.
  • Avoid contact with your dog’s urine. If you have to clean up your dog’s urine in your home, wear gloves and clean the area with a household disinfectant.
  • Encourage your dog to urinate away from standing water or areas where other people or animals will have access.
  • Wash your hands after handling your dog.


At Family Pet Animal Hospital, we dedicate our lives to the health and well-being of our patients.  It is our passion to help our patients live long, healthy, and happy lives.  Additionally, it is our responsibility to educate our clients about the risk factors that affect pets in the Chicago area.  Please contact us for more information about leptospirosis, the available vaccine, or to schedule an appointment.

Additional resources:

Spike in Leptospirosis Cases in Chicago (October 2016)

Leptospirosis and DHPP Vaccinations



N/A.  “Leptospirosis.”  AVMA. American Veterinary Medical Association.  n.d.  Web.  6 Jun 2018.

N/A.  “Chicago Tops Orkin Top 50 Rattiest Cities List for Third Time.” Orkin. Orkin, LLC, 16 Oct 2017. Web. 6 Jun 2018.

Wooten, Sarah J. “Not Your Grandpa’s Canine Leptospirosis Cases.”  Dvm360.  UBM,  19 Jan 2017.  Web.  6 Jun 2018.

N/A.  “Leptospirosis.” Centers for Disease control and Prevention.  Centers for Disease Control and Prevention, n.d.  Web.  6 Jun 2018