Weak Immune System in Cats

A weak immune system in cats, as well as other species, is caused by a deficiency in a type of white blood cell called phagocytes.  These phagocyte cells are an essential part of the immune system, as they engulf foreign invaders contaminating the blood, a process known in the veterinary world as phagocytosis. A deficiency in phagocytosis caused by an infection or an abnormally low number of phagocyte cells present at birth can cause a feline to become especially susceptible to infections of the gastrointestinal and respiratory systems and infections of the skin.

The immune system is your cat’s defense against parasites, viruses, and bacteria of the outside world. When this line of defense is weak or becomes weakened, a feline is more susceptible to developing life-threatening illnesses.

A feline with a weak immune system is healthy overall for the first months of life, but as the feline stops nursing the supply of antibodies disappear and it becomes progressively susceptible to bodily infections. Noted symptoms of weakened immune system in cats include:

• Continuously becoming ill 
• Recurrent infections or infections that fail to respond to conventional treatment
• Stunted growth
• Anorexia
• Lethargy
• Poor hair coat
• Symptoms related to the cause of weak immune system (feline parvovirus, feline leukemia virus or feline immunodeficiency virus)
• Symptoms caused by a contracted infection (bacterial, viral or parasitical)

A weak immune system can either be a congenital disorder that the cat was born with or the immune system can become weakened due to conditions that are known to attack the infection fighting white blood cells, phagocytes. 

Congenital Weak Immune System in Cats

A cat born with an immunodeficiency disorder has an abnormally low number of phagocytes and will have difficulty fighting disease, leading to life-threatening situations. There is no cure for immunodeficiency disorder.

Viral Weak Immune System in Cats

Feline immunodeficiency virus (FIV)

Feline immunodeficiency virus attacks the immune system, causing low red and white blood cell counts. Spread from one feline to another through biting, the cat may not show signs of the infection for months or even years after contracting the virus. FIV infects a cat for life, leading to a deteriorated immune system. 

Feline leukemia virus (FeLV)

FeLV is a worldwide, retrovirus that despite use of vaccines, is still the number one cause of death among cats. FeLV severely suppresses the immune system, leading to conditions such as intestinal inflammation, reproductive disorders, immune-mediated disease, anemia and cancer. 

Feline parvovirus (FPV)

Parvovirus is a severe immune-depressing, viral infection that usually infects a feline short-term. Parvovirus attacks the lymphocytes and neutrophils portion of the white blood cell population, making a feline susceptible to bacterial and fungal infections. 

The diagnosis of a weak immune system in your cat will begin with a review of your feline’s medical history. Your veterinarian will review his or her medical file, but any historical data you possess should be shared with the doctor to pinpoint when the problem began, symptoms, and possible causes. After the veterinarian exchanges notes with you, he or she may proceed to conduct the following:

• A physical examination
• Complete blood count (CBC): a test in which the number of blood cells in a single blood sample are counted to determine the total number of cells. 
• Urinalysis: an examination of the urine. 
• Biochemistry profile: a test that measures the components of blood, providing an overview of most bodily functions. 

Additional diagnostic testing may be completed based on the findings of previous tests. 

Congenital weak immune system in cats has no treatment or cure, and viral associated weak immune system in cats is often not caught early enough to effectively treat the condition. Therefore, no effective treatment has been found to cure weak immune system in cats, but supportive care and prevention have been known to effectively lengthen a feline’s life. 

Your veterinarian may provide treatment for secondary conditions that comes with congenital and viral related weak immune system conditions. 

• Antibiotics to fight bacterial infections
• Antimicrobial medications to fight fungal/yeast infections
• Chemotherapy 

The key to keeping your cat healthy when he or she has a weak immune system is prevention. Isolating your cat from other felines and animals, as well as preventing her from leaving the home is often the first rule of thumb when it comes to weak immune system management. Your veterinarian will advise you to be on the dot with vaccinations and may advise your cat to have additional vaccinations you may not usually ask for. As secondary infections are quite common in cats with depressed immune systems, you can expect your cat to visit the veterinarian often and go through various courses of prescribed medical treatment.

Veterinarians often advise breeders and owners of felines with known immune deficiency conditions to withhold from reproductive practices. Weak immune system conditions can be passed onto future generations if infected cats are allowed to breed.