Bacterial Infection (Leptospirosis) in Cats

6 min read

Leptospirosis in Cats

Leptospirosis is an infection of bacterial spirochetes, which cats acquire when subspecies of the Leptospira interrogans penetrate the skin and spread through the body by way of the bloodstream. Two of of the most commonly seen members of this subspecies are the L. grippotyphosa and L. Pomona bacteria. Spirochetes are spiral or corkscrew-shaped bacteria which infiltrate the system by burrowing into the skin.

Leptospires spread throughout the entire body, reproducing in the liver, kidneys, central nervous system, eyes, and reproductive system. Soon after the initial infection, fever and bacterial infection of the blood develop, but these symptoms soon resolve with the reactive increase of antibodies, which clear the spirochetes from most of the system. The extent to which this bacteria affects the organs will depend on your cat's immune system and its ability to eradicate the infection fully. Even then, Leptospira spirochetes can remain in the kidneys and continue to reproduce there. Infection of the liver or kidneys can be fatal when the infection progresses, leading to severe organ damage. Young cats with less developed immune systems are at heightened risk for severe complications, as well as cats with already compromised immune systems.

The Leptospira spirochete bacteria is zoonotic, meaning that it can be transmitted from an infected animal to humans and other animals. Children are most at risk of acquiring this parasitic bacteria from an infected pet.

Symptoms and Types

  • Sudden fever and illness
  • Sore muscles, reluctance to move
  • Stiffness in muscles, legs, stiff gait
  • Shivering
  • Weakness
  • Depression
  • Lack of appetite
  • Increased thirst and urination progressing to inability to urinate, may be indicative of chronic renal (kidney) failure
  • Rapid dehydration
  • Vomiting, possibly with blood
  • Diarrhea - with or without blood in stool
  • Bloody vaginal discharge
  • Dark red speckled gums (petechiae)
  • Yellow skin and/or whites of eyes – anemic symptoms
  • Spontaneous cough
  • Difficulty breathing, fast breathing, irregular pulse
  • Runny nose
  • Swelling of the mucous membrane
  • Mild swelling of the lymph nodes


The Leptospira spirochete infection occurs mainly in subtropical, tropical, and wet environments. Leptospira spirochetes are most prevalent in marshy/muddy areas with stagnant surface water. Heavily irrigated pastures are also common sources of infection. The infection rate for domestic pets has been increasing in the U.S. And Canada, with infections occurring most commonly in the fall season. Cats typically come into contact with the leptospira bacteria in infected soil or mud, from drinking or being in contaminated water, or from coming into contact with urine from an infected animal. This last method of contact might take place in the wild. Cats that live near wooded areas, or cats that live on or near farms are at a higher risk of contracting the bacteria. Also at increased risk are cats that have spent time around other animals, as in kennels. Otherwise, because most cat breeds do not spend a lot of time near water, infection of the Leptospira spirochete is rare in cats.



Because leptospirosis is a zoonotic disease, your veterinarian will be especially cautious when handling your cat, and will strongly advise you to do the same. Protective latex gloves must be worn at all times, and all body fluids will be treated as biologically hazardous materials. Urine, semen, post-abortion or birth discharge, vomit, and any fluid that leaves the body will need to be handled with extreme caution.

You will need to give a thorough history of your cat's health, including a background history of symptoms, recent activities, and possible incidents that might have precipitated this condition. The history you provide may give your veterinarian clues as to what stage of infection your cat is experiencing, and which organs are being most affected.

Your veterinarian will then order a chemical blood profile, a complete blood count, a urinalysis, an electrolyte panel, and a fluorescent antibody urine test. Urine and blood cultures will also be ordered for examining the prevalence of the bacteria. A microscopic agglutination test, or titer test, will be performed to measure your cat's immune response to the infection by measuring the presence of antibodies in the bloodstream. This will help to definitively identify Leptospira spirochetes and the level of systemic infection that is occurring.

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