Caring For An Immunocompromised Cat

caring for an immunocompromised cat

I recently wrote an article on immunocompromised people who live with cats and way to reduce the risks for those individuals. This article will focus on cats who have compromised immune systems and ways we can keep them healthy.

The immune system is there to protect the cat. It is made up of a number of chemicals,
cells, tissues, and organs which have many roles in defending him against disease-causing organisms as well as removing tumour cells. When the immune system isn’t functioning as it should, invading organisms can take a hold.

There are two types of immune disorders, primary, which are immune disorders the cat is born with or secondary, which are acquired, such as FIV.

What causes some cats to become immunocompromised?

There are a number of causes which may lead immunodeficiency. Age can have an impact on the immune system with very young and geriatric cats having some degree of immunodeficiency. This is normal and as the cat matures so will his immune system.

  • Kittens – Very young kittens are born with immature immune systems, this is entirely normal. As the kitten ages, his immune system will develop. In the meantime, he receives a passive immunity via his mother’s milk.
  • Geriatric cats – At the opposite end of the spectrum are senior cats.


  • Chediak-Higashi syndrome
  • Thymic aplasia
  • Idiopathic (unknown)


  • Feline immunodeficiency virus – A viral infection similar to the HIV infection in humans which replicates in the white blood cells known as T lymphocytes (CD4+ lymphocyte).
  • Feline leukemia virus – A viral infection spreads throughout the body in several phases before entering the bone marrow affecting progenitor cells responsible for the production of red and white blood cells.
  • Feline panleukopenia – This acute viral infection is caused by the feline parvovirus. It has a high mortality rate, but cats who do survive typically go on to have a normal functioning immune system once they are fully recovered.
  • Diabetes Caused by cells which don’t respond appropriately to insulin which is required to move glucose from the blood into the cells. When this occurs, glucose builds up in the blood causing hyperglycemia, which has an impact on the immune system.
  • Medications – Certain medications such as glucocorticoid may be prescribed to treat immune-mediated disease (for example systemic lupus erythematosus), these work by suppressing the cat’s immune system.
  • Cancers of the immune system – Leukemia, lymphoma, multiple myeloma.

What are the symptoms of a compromised immune system in cats?

  • Common and recurrent infections, which may fail to respond to treatment (such as antibiotics)
  • Kittens who fail to grow
  • Lethargy
  • Weakness
  • Weight loss
  • Enlarged lymph nodes
  • Diarrhea
  • Persistent fever

Immunocompromised cats are at risk of infection from organisms which would usually not cause symptoms or only mild symptoms such as:

  • Infections and or clinical symptoms from organisms such as coccidiosis, giardia, toxoplasmosis, salmonella, cryptosporidium.
  • Disseminated disease ( an infection which would normally be local and mild, but spreads through the body) such as histoplasmosis.
  • Parasitic pneumonia from lungworm, toxoplasmosis, liver flukes and roundworms.

How are immune disorders diagnosed?

If your cat has a history of infections or is displaying other symptoms which raise your veterinarian’s index of suspicion he will need to perform some tests to determine the cause. These may include:

  • Complete blood count, biochemical profile and urinalysis to evaluate the overall health of your cat, look for abnormalities in the blood cells and signs of infection.
  • Blood tests for FIV or FeLV.
  • Bone marrow biopsy.

How do I care for an immunocompromised cat?

A cat whose immune system isn’t working as well as it should need some extra precautions to reduce his risks of catching diseases or parasites. Some ways you can do this include:

  • Regular veterinary checkups – Bi-annual wellness visits are necessary for cats whose immune systems are compromised.
  • Always watch for minor signs of sickness and act – Pet owners who have immunocompromised cats should never use a wait and see approach when it comes to the health of their cat. At the first sign of any symptoms, the cat should be seen by a veterinarian.
  • Stay up to date with parasitic treatments – All cats in the household should receive regular flea and worm treatments to prevent parasites. Fleas are able to transmit a number of diseases to cats while parasitic worms can weaken an already weak cat.
  • Vaccinating your cat – Discuss with your veterinarian your cat’s vaccination schedule. He may need to tailor it to your cat’s specific needs, this may include only giving your cat killed vaccines.
  • Avoid raw meat – Do not feed your cat raw meat to reduce the risk of foodborne bacterial or parasitic infections. A good quality commercial diet is recommended for immunocompromised cats.
  • Avoid stress – A cat with a compromised immune system needs to live in an environment that is stress-free.
  • Keep your cat indoors – Immunocompromised cats should not be allowed to go outside or to hunt. Both of which expose them to potential risks of infection.
  • Don’t adopt new pets – It is recommended that an immunocompromised cat be the only pet in the household if possible. Certainly, it is not a good idea to introduce new cats to the home of an immunocompromised cat.
  • Blood transfusions – If your cat’s red or white blood cells drop too much a blood transfusion may be necessary.
  • Regularly disinfect – Cleanliness and hygiene is even more important in the cat who is immunocompromised. Regularly disinfect bowls, litter trays, floors, bedding and cat toys. See here for disinfectants which are safe for cats.
  • Wash your hands – If you have been in contact with other animals, make sure hands are washed before touching your own cat. Hands should also be washed after gardening, and before/after preparing food.

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