Cats can succumb to a variety of feline-specific illnesses, including feline leukemia virus (FeLV), feline immunodeficiency virus (FIV), and feline infectious peritonitis (FIP). While FeLV and FIV are seen occasionally, usually in stray cats who have lived outdoors, FIP is, fortunately, relatively rare, because the disease is almost always fatal.

What is feline infectious peritonitis?

FIP is caused by a certain strain of feline coronavirus. Coronaviruses are a common virus group that often cause upper respiratory or gastrointestinal illness. In humans, coronaviruses are a frequent cause of the common cold. 

In cats, most strains do not cause disease signs, and are referred to as feline enteric coronavirus, because they usually cause mild, self-limiting diarrhea. In 5% to 10% of cats infected with a coronavirus strain, the virus mutates, or the immune system responds inappropriately, leading to FIP development. With help from the antibodies supposed to protect the cat, the virus infects the white blood cells. This unique relationship between the immune system and the virus is unlike any other virus, in people or animals. As the infected white blood cells migrate, an intense inflammatory reaction occurs around the vessels in the commonly affected tissues, including the abdomen, kidneys, or brain. 

Is my cat at risk for developing feline infectious peritonitis?

Any cat who carries a coronavirus strain is potentially at risk for developing FIP, but the disease is more common in immune-compromised cats, such as kittens, geriatric cats, or cats who already have FeLV. Most cats who develop FIP are under 2 years of age, and live in groups or colonies, such as animal shelters and catteries. The virus can be passed through saliva or feces, but is most commonly transmitted when an infected mother cat passes a coronavirus to her 5- to 8-week-old kittens.

What are feline infectious peritonitis signs?

FIP generally has two forms, wet and dry, although some cats may have signs of both. Early FIP signs are vague, and include fever, lethargy, inappetence, and a rough hair coat. In the beginning stages of wet, or effusive, FIP, signs may appear similar to the dry, or non-effusive, form, including:

  • Weight loss
  • Persistent fever
  • Anemia
  • Lack of appetite
  • Depression

In FIP’s dry form, inflammation generally occurs around the brain and the eyes, which can cause neurological issues, and bleeding in the eyes.

As the wet form progresses, the cat typically starts to rapidly decline. FIP’s wet-form signs include:

  • Fluid accumulation in the abdomen
  • Less commonly, fluid accumulation in the chest
  • Difficulty breathing
  • Pot-bellied appearance 

Since FIP signs can be vague, and indicate many disease processes, a full physical exam and diagnostic testing is required for accurate diagnosis.

How is feline infectious peritonitis diagnosed?

Although a variety of tests can detect coronavirus antibody presence, no simple diagnostic test can differentiate between the coronavirus strains. A positive result means only that the cat has been exposed to a coronavirus, but not necessarily to a strain that causes FIP. Only a biopsy of affected tissue can definitely diagnose FIP in cats. Most often, we rely on the clues from a thorough physical exam, history, clinical signs, examination of chest or abdominal fluid if present, blood work results, and a positive coronavirus antibody titer.

How is feline infectious peritonitis treated?

Once clinical signs develop, FIP is generally incurable and fatal. Supportive treatment may help improve the cat’s quality of life for some time, but euthanasia is often the most humane course of action to prevent suffering. Most cats who have FIP in its wet form die less than two months from the onset of signs, although those with a mild case of dry-form FIP can survive longer. 

Can feline infectious peritonitis be prevented?

An FIP vaccination is available, but of little value, as it can be given only to kittens 16 weeks or older. By that age, most kittens are already exposed to coronavirus, and can develop FIP. The best ways to prevent your cat from getting FIP include:

  • Keeping her as healthy as possible through routine preventive care and appropriate vaccinations
  • Minimal exposure to infectious agents
  • Cleaning and disinfecting litter boxes regularly
  • Preventing overcrowding
  • Limiting stress
  • Proper nutrition
  • Avoiding keeping large groups of cats

Keep your cat healthy and happy, and help prevent FIP, by staying on top of her routine preventive care. To schedule a wellness visit for your feline friend, or if she is exhibiting FIP signs, contact your family veterinarian. If your cat needs emergency care, give us a call or or stop in.