Most Deadly Cat Diseases12 min read


Donna Kennedy, Owner/Author


Hi, my cat-loving friends. Do you know about the Most Deadly Cat Diseases? I

Most Deadly Cat Diseases-Would You Recognize The Signs?

Precious Furbaby

know this is not something we want to think about, but it needs to be addressed.

As a cat owner, let me ask you a question, Would you know the signs and symptoms of a cat that has:

  1. Avian Influenza 
  2. Cancer in Cats
  3. Diabetes Mellitus 
  4. Feline Immunodeficiency Virus (FIV)
  5. Heart Valve Dysplasia
  6. Feline Leukemia (FeLV)

This is just a few diseases that can kill our feline friends if left untreated or undiagnosed.

So, let’s find out what the signs and symptoms of these deadly diseases are. Ready to get started? Let’s go!

1. Avian Influenza Virus

Picture Of One Of The Most Deadly Cat Diseases In Virus Form

Avian Influenza Virus-H5N1

If a cat gets this virus and it is left untreated, death will surely follow! Cat’s can get this deadly disease by eating uncooked poultry that is infected or coming in contact with waterfowl that are infected.

The specific virus they get is H5N1, which is a subtype of Avian Influenza. It primarily affects the liver and lungs.


  • Fever
  • Lethargy
  • Dyspnea (shortness of breath)


  • Neurological symptoms such as going around in circles (Ataxia)
  • Panting
  • Convulsions
  • Renal Congestion
  • Pulmonary Congestion
  • Edema
  • Pneumonia
  • Cerebral Congestion
  • Conjunctivitis
  • Hemorrhaging in the intestines

FYI: This is seen in cats with high doses of the virus and cats infected with low doses may not show any symptoms, but they can still transfer small doses of the virus.

Treatment and Prevention

You can get your cat vaccinated against the H5N1 virus. This is a horrific virus and your furbaby should be inoculated so they can be protected!

Of course, no vaccination is 100% perfect, which means that your kitty could still transfer small doses of the virus.

Should your cat show ANY signs or symptoms of this disease, PLEASE put them in isolation and keep them indoors!

It is imperative that you make an appointment with your veterinarian immediately so they can test your pet for the H5N1 virus.

FYI: Should there be a possibility that your furbaby has the Avian Influenza Virus, you should wear gloves, masks, and goggles to avoid direct contact with the animal. Then you must clean ANY surfaces that your kitty has come in contact with using standard household cleaners. (IE: Bleach)

If your furbaby test positive for this virus, your Veterinarian will decide the best course of treatment which may be Oseltamivir in 75 mg/60 kg twice a day. Dosing of antiviral medications is based on the species of the pet.

2. Cancer in Cats

Lymphoma Cancer Is Another One Of The Most Deadly Cat Diseases

Kitty Receiving Cancer Treatment

Cancer is not as prevalent in cats as it is dogs, but cats can get cancer. Since cats are very good at masking illnesses they may get, it’s usually harder to detect.

Now cancer in cats is the leading cause of their demise, especially among our older furbabies.

Most often in cats cancer will usually manifest itself in the form of a lump/bump on any part of the kitty’s body.

Depending on the type of tumor that the kitty may have, it can spread to other areas of the body and rapidly grow.

Now if the cancer is diagnosed early enough, it can be treated successfully. Cancer accounts for 32% of deaths in our furbabies that are over 10 years old.

The reason cats get cancer is unknown, but the Feline Leukemia Virus (FeLV) is suspected of being the reason cats get cancer.

The most common cancer seen in cats is Lymphoma. (Affects the Lymph Nodes)


  • Loss of Appetite
  • Chronic Weight Loss
  • Stiffness
  • Ravenous Hunger
  • Oral Odor
  • Coughing or dyspnea


  • Diarrhea
  • Vomiting
  • Unexplained discharge/bleeding from the body
  • Problems Urinating or pooping
  • Problems eating and swallowing
  • A sore that will not heal up
  • Changes in the shape and size of a lump
  • Changes in their bladder or bowel habits

Treatment of Cancerous tumors depends on size and type. It could be anything from the surgical removal of the tumor, radiation, chemotherapy, or immunotherapy.

So, if you notice any of the signs/symptoms, please get your cat to the Veterinarian as soon as possible to get them checked out!

Their survival may depend on quick diagnosis and treatment!

3. Diabetes Mellitus

Diabetes Mellitus Is Among The Most Deadly Cat Diseases

Feline Receiving An Insulin Injection

This type of diabetes is a chronic disease in our feline friends and is less common in cats than dogs.

Approximately 1 in 230 cats are affected by diabetes mellitus. In cats 80-90% experience something similar to type 2 diabetes, but by the time it is discovered and diagnosed the kitty is severely insulin-dependent.

Thank goodness this disease is very treatable and if treated right, there is no reason your cat cannot experience a normal life.

In cats that have type 2 diabetes if treated promptly the treatment may lead to the cat no longer needed the insulin. This is called diabetic remission.

If left untreated, this condition will lead to the cat having weak legs, and eventually ketoacidosis (abnormally high levels of acid in the blood due to the presence of “ketone bodies.”) malnutrition, and/or dehydration, and death.


  • Sudden weight loss/weight gain
  • Excessive drinking of water/urination
  • Ravenous appetite-up to 3 times what they normally eat
  • Complete loss of appetite


  • Cat starts to waste away-the body starts using its own fat and muscle to survive
  • Cat becomes lethargic
  • Noticeable acetone or fruity-smelling breath-acute (sudden onset) of ketoacidosis and or dehydration.

FYI: This is a medical emergency with a high fatality rate!! You cannot treat this at home!! This situation will require emergency care such as fluid therapy, insulin, management of current symptoms and 24-hour observation in the hospital!!!!

This is definitely one of the Most Deadly Cat Diseases and should be treated as such!

4. Feline Immunodeficiency Virus (FIV)

One Of The Most Deadly Cat Diseases Is Feline Immunodeficiency Virus

Cat Having Blood Drawn

This disease compromises the cat’s immune system. Now cats can live for years with this disease before they start to show any signs/symptoms.

FIV is slow-acting, but once the disease takes over it severely weakens the kitty’s immune system opening them up for secondary diseases.

However, if your furbaby receives supportive medical care and is kept in a stress-free home, they can live a good comfortable life before the disease reaches chronic stages.


  • Weight loss
  • Fever
  • Anemia (low hemoglobin)
  • Poor appetite
  • Hair loss
  • Frequent urination
  • Sneezing
  • Changes in their behavior


  • Enlarged lymph nodes
  • Fur is disheveled
  • Diarrhea
  • Conjunctivitis (Eye inflammation)
  • Gingivitis (red irritated gums)
  • Redness to the skin
  • Stomatitis (mouth inflammation)
  • Dental disease

Cat’s catch this disease by getting into aggressive fights, (i.e. especially during the mating season) which result in someone getting bitten causing deep wounds.

Tomcats become very territorial during this time and are more likely to contract the disease than the females because of the aggressive fights they encounter.

It would be a very good idea to keep your cats indoors during this time of the year, which is Springtime to avoid these fights.

Mama cats can also pass this onto her kitten’s if she is infected with the FIV disease. But not to worry, this is not a common way this disease is spread.

Also, it is not spread through eating out of the same bowls, litter boxes, or other social modes of contact.

If you should notice any of these signs or symptoms, please schedule your cat an appointment with your veterinarian right away so they can be tested.

Keep them away from other cats until you have a definitive diagnosis as to whether or not your furbaby is infected with the FIV or not.

This is to avoid spreading the disease to other cats that may be in your neighborhood.

Your Veterinarian will determine your kitty’s diagnoses by performing a blood test. If your furbaby test positive, then they may start these treatments:

  • Fluid and electrolyte replacement
  • A healthy diet for good nutrition
  • Immune-enhancing drugs
  • Anti-inflammatory drugs
  • Secondary infection drugs
  • Medication for parasite control

If your furbaby tests positive for FIV, you will need to take your cat to the Veterinarian at least twice a year for a wellness check.

Make sure you watch for changes in your kitty’s behavior or health no matter how minor you may think they are.

Keep your cat indoors for their protection of other diseases as well as for the protection of the other cats.

Make sure you feed your kitty a well-balanced nutrition healthy diet based on your Veterinarian’s recommendations.

FYI: Absolutely NO RAW FOOD AT ALL! The reason is that bacteria and parasites live in uncooked eggs and meat and this can be dangerous to a pet with an already compromised immune system!

If this disease is left untreated it will ultimately claim your cat’s life.

5. Heart Valve Dysplasia In Cat’s

Echocardiography Will Help To Diagnose One Of The Most Deadly Cat Diseases


This is a congenital heart defect that the animal is born with which affects the aortic, pulmonary, and tricuspid valves.

With the dysplasia of the mitral and tricuspid valves, it can cause the blood to leak better known as stenosis (narrowing of the blood vessel).

These valves can become thickened, be shortened, or have notched valves causing an atrial septal defect, or inflammation of the right atrial epicardium.

The most common defect in cats is mitral valve stenosis. The leakage of blood will eventually lead to an enlarged heart.


  • Stunted growth
  • Exercise intolerance


  • Loud breathing/trouble breathing
  • Coughing
  • Fluid or swelling in the belly
  • Fainting

Should your furbaby show any signs or symptoms of this disease, you will need to make an appointment with your veterinarian as soon as possible.

The Veterinarian will then do a CBC (Complete blood count) and a urinalysis. Be sure to give your vet. a complete history of your kitty.

For further diagnosis, the doctor will want to view your cat’s heart by doing an X-ray to check the enlargement of the valves.

Echocardiography will be used to determine if there is an abnormal flow of blood through the heart and ECG (Electrocardiograph) to determine if the animal has an abnormal rhythm to see which side of the heart is being affected.

Your cat’s Veterinarian may have to put your furbaby on diuretics to help with fluid retention caused by congestive heart failure (CHF) and a vasodilator to dilate the blood vessels.

Your cat may also be put on a medication called digoxin to control the heart rate as well.

The long term prognosis for this disease is guarded to poor. It depends on the severity of the disease.

6. Feline Leukemia Virus (FeLV)Feline Leukemia Virus Tops The Most Deadly Cat Diseases 

This disease can be transmitted from one cat to another through their saliva and nasal secretions.

If your kitty’s immune system is unable to fight off this virus, it can cause other diseases that can be potentially deadly to your furbaby.

Cat’s that have a healthy immune system are usually able to fight off the disease and never get sick, but however, they can become a carrier.


  • Loss of appetite
  • Lethargy
  • Fever
  • Weight loss
  • Uneven pupils
  • Skin infections
  • Bladder infections
  • Respiratory infections


  • Runny eyes
  • Runny nose
  • Sneezing
  • Coughing
  • Skin Lesions
  • Fatigue
  • Anemia
  • Diarrhea
  • Jaundice
  • Seizures
  • Swollen lymph nodes

As you can see this is another one of the Most Deadly Cat Diseases and should be taken very seriously!

Should you feel that your furbaby is showing any of these signs/symptoms, you know what to do…Get them to the Veterinarian to be tested for this disease.

Your Veterinarian will diagnose this by doing a blood test. You will find out the results in just a few minutes.

“ALL” cat’s should be tested for this disease, because even healthy cats can have FeLV. Don’t be fooled by a healthy cat, because they can test positive too.

If your cat tests positive, they will need to be put on medications to protect them as well as be kept indoors.

You will also need to keep your cat’s vaccinations up to date to keep them free of parasites as well as other diseases.

FYI: DO NOT feed your cat any raw food, because raw food usually contains bacteria and parasites that could be dangerous to your furbaby!

This disease has 6 stages that the cat will go through if not treated that will ultimately lead to their demise. They are:

  1. The virus enters the cat through the nose/mouth
  2. Then the virus enters into the bloodstream
  3. Then it enters the lymphoid system (which is the antibodies that fight Cancer cells) which gets distributed throughout the body
  4. Now the hemolymphatic system and intestines are infected. Now if the kitty’s immune system is unable to fight off the disease, the next 2 steps are:
  5. The bone marrow becomes infected
  6. Now the cat’s whole body becomes infected-not good

So, PLEASE if you think your furbaby has any signs/symptoms it is imperative that you seek medical attention for your cat!!

Donna’s Final Thoughts

Whew!  I finally got through 6 of the Most Deadly Cat Diseases. Just so you know, I barely scratched the surface of the diseases our fur babies can get.

So, whatever you do, if you suspect that your cat has any of these diseases I highly recommend that you get them to your pet’s Veterinarian ASAP!

If you get a new kitty, the best thing that you can do is go ahead and get them to the doctor and have them checked out.

Go ahead and get all of their immunizations that they are due and keep them up to date!

This is the best thing that you can do for your furbaby to help keep them healthy and well.

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See ya again real soon,

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