Caring For An Immunocompromised Cat

I recently wrote an article on immunocompromised people who live with cats and ways 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 and is made up of several chemicals, cells, tissues, and organs which have many roles in defending against disease-causing organisms and tumour cells. When the immune system isn’t functioning as it should, invading pathogens can take 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?

Several causes may lead to immunodeficiency. Age can have an impact on the immune system with very young and geriatric cats having some degree of immunodeficiency, which is normal, 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.
  • Panleukopenia – This acute viral infection is caused by the feline parvovirus and has a high mortality rate. Cats who do survive typically go on to have a healthy functioning immune system once they are fully recovered.
  • Diabetes – Caused by cells that 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.


  • Frequent 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 that would usually not cause symptoms or only mild symptoms such as:


The veterinarian will perform a complete physical examination of the cat as well as obtain a full medical history from you. If your cat has a history of infections or is displaying other symptoms which raise your veterinarian’s index of suspicion.

Diagnostic workup:

Caring for an immunocompromised cat

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

  • Schedule 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. Seek veterinary care at the first sign of any symptoms.
  • Stay up to date with parasitic treatments: All cats in the household should receive regular flea and worm treatments to prevent parasites. Fleas can transmit several diseases to cats while parasitic worms can weaken an already weak cat.
  • Vaccinate 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. Feed a premium commercial diet.
  • Avoid stress: A cat with a compromised immune system needs to live in a stress-free environment.
  • Keep your cat indoors: Do not allow immunocompromised cats to go outside or hunt. Both of which expose them to potential risks of infection.
  • Don’t adopt new pets: If possible, the immunocompromised cat should be the only pet in the home. Certainly, it is not a good idea to introduce new cats to the home of an immunocompromised cat.
  • Blood transfusions: For cats with significantly low white or red blood cell counts.
  • Practice good husbandry: Cleanliness and hygiene are even more important for the immunocompromised cat. Regularly disinfect bowls, litter trays, floors, bedding and cat toys. See here for disinfectants that are safe for cats.
  • Wash hands: If you have been in contact with other animals. Wash hands after gardening and before/after preparing food.

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  • Julia Wilson, 'Cat World' Founder

    Julia Wilson is the founder of Cat-World, and has researched and written over 1,000 articles about cats. She is a cat expert with over 20 years of experience writing about a wide range of cat topics, with a special interest in cat health, welfare and preventative care. Julia lives in Sydney with her family, four cats and two dogs. Full author bio

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