Bacterial Infection (Leptospirosis) in Cats

By PetMD Editorial on Feb. 4, 2009

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.


Your cat will need to be hospitalized if it is severely ill from this infection. Fluid therapy will be the primary treatment for reversing any effects of dehydration. If your cat has been vomiting, an anti-vomiting drug, called an antiemetic, may be administered, and a gastric tube can be used to give nourishment if your cat's ability to eat or keep food down is being hindered by the illness. A blood transfusion may also be necessary if your cat has been severely hemorrhaging.

Antibiotics will be prescribed by your veterinarian for a course of at least four weeks, with the type of antibiotic dependent on the stage of infection. Penicillins can be used for initial infections, but they are not effective for eliminating the bacteria once it has reached the carrier stage. Tetracyclines, fluoroquinolones, or similar antibiotics will be prescribed for the carrier stage, since they are better distributed into the bone tissue. Some antibiotics can have side effects that appear serious, especially those drugs that go deeper into the system to eliminate infection. Be sure to read all of the warnings that come with the prescription, and talk to your veterinarian about adverse indications you will need to watch for. Prognosis for recovery is generally positive, barring severe organ damage.

Living and Management

A vaccination for the prevention of the leptospirosis infection is available in some areas. Your veterinarian can advise you on the availability and usefulness of this vaccine. Make sure to inspect kennels before placing your cat in one – the kennel should be kept very clean, and should be free of rodents (look for rodent droppings). Urine from an infected animal should not come into contact with any other animals, or people. Animals that are kept in close quarters are going to be in contact with other animals' urine, even under the best circumstances, so cleanliness needs to be the utmost consideration when choosing your kennel.

Activity should be restricted to cage rest while your cat recovers from the physical trauma of this infection. Leptospirosis is a zoonotic disease, transmissible to humans, and other animals via urine, semen, and post-abortion discharge. While your pet is in the process of being treated, you will need to keep it isolated from children and other pets, and you will need to wear protective latex gloves when handling your pet in any way, or when handling fluid or waste products from your pet. Areas where your pet has urinated, vomited, or has possibly left any other type of fluid should be cleaned and disinfected thoroughly with iodine-based disinfectants or bleach solutions. Gloves should be worn during the cleaning process and disposed of properly afterwards.

Finally, if you do have other pets or children in the home, they may have been infected with the leptospira bacteria and are not yet showing symptoms. It may be worthwhile to have them (and yourself) tested for the presence of the bacteria. It is also important to keep in mind that leptospires may continue to be shed through the urine for several weeks after treatment and apparent recovery from the infection. Appropriate handling practices are the best way to prevent the spread of infection or reinfection.

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