Leptospirosis in Cats-Causes, Symptoms and Treatment


Leptospirosis in cats

Leptospirosis is a zoonotic infection (one which can be passed on from animals to humans) caused by spirochete (corkscrew-shaped) bacteria of the genus Leptospira. Leptospira causes flu-like symptoms, Weil’s syndrome (jaundice, kidney failure, bleeding, myocarditis, and arrhythmias), meningitis and pulmonary hemorrhage in people.

There are more than 250 pathogenic (disease-causing) serotypes of Leptospira. The global distribution is worldwide, but it is most prevalent in tropical and sub-tropical areas with heavy rainfall as well as developing countries. Common areas include Latin America, Indian subcontinent, Melanesia, Micronesia, Polynesia and Australasia, Southeast Asia and Eastern Europe. 


Commonly affected animals include rodents, opossums, skunks, raccoons, possums, cattle, deer, sheep, horses, and dogs. Farm animals are a common source of leptospirosis in humans.

Transmission occurs via the urine-oral, direct contact or inhalation. Bacteria are shed in an infected animal’s urine, which contaminates bodies of water and soil. Outbreaks can occur after heavy rain or flooding.

  • Oral: Consumption of contaminated prey, food or water.
  • Direct contact: Bacteria from contaminated urine, soil or water which enters the body via breaks in the skin or through the mucous membranes (eyes, nose, gums) or during mutual grooming.
  • Inhalation: Aerosol infection can occur if the cat inhales bacteria from a contaminated source such as soil.

Clinical illness in cats is uncommon, which is thought to be due to a natural resistance as well as a cat’s aversion to water; however, it is an emerging disease in dogs and humans. Cats can be exposed to the bacteria in the urine of an infected household dog.

Once inside the cat, the bacteria migrate to the bloodstream and lymphatic tissue and rapidly spread throughout the body where it invades many organs and tissues. By 8 hours, the number of bacteria present has doubled.

In some infected hosts, bacteria numbers are maintained (and do not drastically increase in numbers) becoming a carrier, and continually shedding bacteria in the urine which goes on to infect other animals or humans. The bacteria remain viable in the environment for months or even years. 


Symptoms of leptospirosis in cats

The incubation period is 2-24 days, although most infected cats remain asymptomatic. Leptospirosis is a multisystemic disease with a range of possible symptoms depending on the organ(s) affected, the age and the immune status of the cat.  The disease occurs in two phases: 

Phase 1 (acute):

Phase two (immune):

  • Jaundice (yellow gums)
  • Speckled gums due to thrombocytopenia (low blood platelets)
  • Eye discharge
  • Nasal discharge
  • Increased thirst and urination followed by absent urination as the kidneys fail
  • Miscarriage in pregnant females


The veterinarian will perform a complete physical examination of your cat and obtain a medical history.

Diagnostic workup:

Baseline tests: Complete blood count, biochemical profile and urinalysis to evaluate the overall health of the cat. These may reveal dehydration, low blood platelets, elevated BUN or liver enzymes.

Microscopic agglutination test (MAT): This is the most common test used in the diagnosis of leptospirosis. The test detects antibodies specific for the leptospira bacteria. Two tests are performed two weeks apart, which should show an increase in antibodies (four-fold).

Polymerase chain reaction (PCR): A test which takes a small sample of DNA and amplifies it millions of times to identify the pathogen.

Cultures: Samples of urine and blood are cultured to detect the strain of bacteria and in some cases, its sensitivity to different antibiotics. 


Because of the zoonotic nature of leptospirosis, great care must be taken when caring for an infected cat. Wear protective gloves when handling any fluids or discharge, such as vomit and cat urine.

Antibiotics are used to kill the bacteria; treatment occurs in two phases — penicillins to treat circulating leptospira followed by tetracyclines. Antibiotic therapy lasts 3-4 weeks.

Severely ill cats will be treated in hospital with supportive care, which may include fluids to treat dehydration and nutritional support for a cat who is not eating. For cats with severe low blood platelets, a blood transfusion may be necessary. 


Leptospirosis does not live on dry surfaces for long but can survive in water for up to six months. The following disinfectants are effective against leptospirosis.

  • Bleach (sodium hypochlorite, calcium hypochlorite or sodium dichloroisocyanurate) – Dilute at a rate of 1:10
  • F10-Benzalkonium chloride and polyhexanide
  • Virox, Accel – Accelerated hydrogen peroxide