How Common Is Feline Leukemia? ( And Other Questions )

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 Severe viral disease in cats, leukemia is a condition that unfortunately still kills many small felines. What virus is it due to? How common is feline leukemia? How can your cat get leukemia? What are the signs that make it possible to recognize this disease? Can leukemia in cats be cured? How to protect your cat from leukemia? We give you the central notions about the disease to better protect it.

how common is feline leukemia


The answer to the critical question, how common is feline leukemia, is that it is unfortunately very common.

Feline leukemia virus is one of the most common infectious diseases in cats. Between 2% and 3% of cats in the United States have been exposed to this virus. However, cats sick or at high risk for other reasons have an infection rate of almost 30%. 


Feline leukemia is a severe infectious disease caused by a virus that affects cats worldwide. This disease can appear in various forms and even kill affected cats.


The causative agent of feline leukemia is FeLV (for Feline Leukemia Virus or feline leukemia virus). It is an RNA virus of the Retrovirus family, with four subgroups, each causing different manifestations explaining the variability of the forms of the disease.

how common is feline leukemia

Once it is expressed, the clinical signs observed can be:

General impairment: depression, weight loss, dehydration, fever.

Respiratory impairment: respiratory distress, increased respiratory rate.

Damage to the central nervous system, including the eyes, with different pupil openings (anisocoria), drooping of the upper eyelid, depression of the eyeball (Claude Bernard Horner syndrome), uveitis, mydriasis.

Damage to the spinal cord, reproductive disorders (abortions, infertility, etc.), cardiac signs (tachycardia, anemia), digestive disorders (vomiting, diarrhea), and finally, a significantly increased risk of cancers (such as lymphomas, for example ). 


 Now, after learning the answer to the question of how common is feline leukemia, it's time for how your cats to catch this disease. This disease is caught in contact with an infected cat through their saliva while licking, biting, or sharing the same bowl. Transmission can also occur through breastfeeding or in utero during gestation. Breeding or shelter cats are, therefore, more exposed than others. On the other hand, the virus is not very resistant in the external environment, good disinfection is enough, so it is unlikely that your pet will catch it in a veterinary clinic by going after an infected cat.

Some wild cats can be affected (lion, tiger, etc.), but the virus is not transmitted to other species such as humans. The disease usually appears in cats aged 3 to 5 years.

The virus passes throughout the body, into the tissues of the immune system and the bone marrow. If the immune system is effective, cat will eliminate the virus without the disease breaking out. The disease can remain silent for several years. But beware, seropositive cats without clinical signs are contagious.

Clinical signs appear when the infection develops, and the immune system cannot defend itself (immunosuppression).


Feline leukemia: The only method is to have your veterinarian carry out tests. The only plan is to have your veterinarian carry out tests to get a diagnosis quickly if you see that your cat is suddenly less fit.

There is indeed the ELISA test (which looks for a FelV protein in the blood) very specific and quickly done at the clinic by your veterinarian, to be repeated after four months if it is positive, to make the difference between viremia transient and permanent damage (and to be completed by other tests depending on the clinical signs);

PCR tests (which search for viral DNA or RNA in cells) to assess the viral load and, therefore the level of infection activity;

And the direct immunofluorescence test, to complete the result of the ELISA test for example.


There is no specific treatment, but so-called symptomatic treatments of the manifestations observed depend on the type of damage. Leukemia is an incurable disease that your cat will carry throughout its life.

The treatments used are used to manage the consequences produced by the virus: these are fluid therapy (infusion), the administration of rehydrating products, antiemetic and antidiarrheal drugs, and adjuvant treatment products for these drugs, food intake palatable, antibiotics, transfusions, chemotherapy.

 Immunomodulators (antivirals such as interferon) do not show systematic efficacy and remain expensive.

Depending on your cat's damage and resistance level, an infection may remain latent, and the disease may show relatively long remission phases. On the other hand, the prognosis is inferior in the case of lymphomas or, worse, leukemia.

how common is feline leukemia


If your cat is a kitten, it is best to have it tested as soon as he is adopted, and if it is negative, to have it vaccinated immediately, from the age of 2 months. The vaccine does not entirely protect 100%, but it reduces the risk of severe forms of the disease.

If your cat is an adult, the procedure is the same.

If your cat is infected without you knowing it, the vaccine will not make it worse, but it will be useless. On the other hand, it will be even more critical to vaccinate an infected cat against other diseases (Chlamydiosis, typhus, coryza) at higher frequencies than for a healthy cat and to isolate it to protect it from other diseases such as toxoplasmosis, FIV infection…

Cats vaccinated against FeLV are not positive in ELISA or PCR tests.


That is to say, a hidden defect severe enough to lead to the nullity of the sale and, therefore the return of the cat to the breeder against reimbursement of the amount paid. For infection with the feline leukemogenic virus (FelV), the time limit for taking action and filing a lawsuit is 15 days after having established a diagnosis of suspicion by your veterinarian.

So, even if he has no clinical signs, have your cat tested and vaccinated to protect him and avoid contamination, especially if he goes out.

Other Deadliest Diseases In Cats

Cats can suffer from diseases with a high mortality rate or are pretty severe if they are not diagnosed and treated in time, especially when they are very young, very old, or immunocompromised. Many of these infectious diseases can be prevented with a proper vaccination plan. Others can be diagnosed early with routine check-ups at the veterinary center, so preventive medicine is crucial to avoid the most deadly diseases in cats.

Continue reading this Petguin article to learn about the most deadly diseases in domestic cats and stray cats: cancer, feline leukemia, feline immunodeficiency, feline rhinotracheitis, kidney disease, feline infectious peritonitis, and rabies.


Cancer is not only a disease with high mortality, but it is also one of the most common cat diseases. Cancer, or uncontrolled cell overgrowth due to a genetic mutation of one or several cell types in a specific location, can be truly deadly, especially those types of cancer with the ability to spread through the bloodstream to other neighboring organs such as the lung, kidney, or bone (metastasis).

In cats, the most frequent tumors are lymphomas, associated or not with the feline leukemia virus, squamous cell carcinoma, breast cancer, intestinal adenocarcinoma, soft tissue sarcoma, osteosarcoma, and mast cell tumor.


Treatment of cancer in cats will depend on the type in the question and whether or not distant metastases have occurred. In resectable tumors, the treatment will be complete surgical removal together or not with chemotherapy.

If metastasis has not yet occurred, the best option is chemotherapy using specific cytotoxic drugs for each cancer. For feline lymphoma, several protocols combine medications of this type to kill rapidly dividing tumor cells, such as the CHOP protocol or the COP. In other cancers, such as squamous cell carcinoma, cryosurgery can be used. In contrast, in others, the use of radiotherapy or electrochemotherapy can also improve the life expectancy of the affected cat.

Suppose there are metastases and the cancer is already very advanced. In that case, the prognosis is inferior. Many cats will not withstand chemotherapy because they are weak and have organic involvement, so only symptomatic treatment could be instituted to improve their quality of life.

Feline immunodeficiency

Another deadly disease in stray and domestic cats because it is highly infectious is feline immunodeficiency. It is caused by a lentivirus that spreads after very close contact through blood and saliva, through bites and wounds, being especially common among stray cats due to fights over females or territories.

After infection, the virus produces a viremia (virus in the blood) that produces an immune response in the cat, which then passes into a subclinical phase that can last for years. Still, it progressively destroys the cat's CD4+ T lymphocytes until levels reach a minimum, at which point acquired immunodeficiency syndrome or AIDS occurs, making the cat very susceptible to infections and immune-mediated oral and respiratory diseases and greatly increased mortality rates.


As with the leukemia virus, there is also no specific drug against this virus, the goal of treatment being to stabilize the cat, maintain a good quality of life and correctly manage the complications and consequences of immunosuppression.

Recombinant feline interferon omega may also be helpful for its immunomodulatory and antiviral properties, as well as the use of vitamin complexes that include evening primrose oil. However, secondary infections must be controlled immediately with antibiotic therapy, which is usually prolonged due to immunosuppression.

Feline rhinotracheitis

Feline rhinotracheitis is caused by feline herpesvirus type I (HVF-1), a microorganism that can remain dormant within the cells of the infected cat and is spread by secretions between cats, and contaminated objects such as clothing or hands.

Generally, it produces an upper respiratory picture, with nasal discharge, sneezing, rhinitis, fever, conjunctivitis, keratitis, corneal ulcers, protrusion of the third eyelid, and corneal sequestrations that are not fatal in immunocompetent individuals. However, young kittens are especially vulnerable, where the virus can cause pneumonia with severe viremia that ends up causing sudden death.


Feline herpesvirus therapy is based on antivirals, the most influential being famciclovir at a dose of 40 mg/kg for three weeks, being higher (62.5 mg/kg) in kittens and cats with kidney disease.

When corneal ulcers are present, tobramycin should be used as a broad-spectrum topical antibiotic, triple- ocular antibiotic, or more selective antibiotics for infected or complicated ulcers. Corneal surgery should be performed when ulcerative keratitis is chronic and corneal sequestration has occurred. Anti-inflammatories and L-lysine can also be given to inhibit arginine, necessary for the replication of the virus, although the most recent studies cast doubt on its efficacy.

Renal disease

Kidney disease is another deadly disease in cats, with the chronic disease being especially common in cats over seven years of age and acute disease in young cats. It occurs after poisoning, dehydration, infections, or various diseases. The loss to a greater or lesser degree of renal filtration capacity is severe. Since the toxins filtered by the kidney remain in the body, there is an increase in blood pressure and electrolyte imbalances, causing damage and associated clinical signs that can end up with the life of your little feline.


The treatment of kidney disease will depend on whether it is an acute or chronic disease. Thus, treatment of the acute form includes the following:

Control dehydration with fluid therapy.

Add calcium gluconate or sodium bicarbonate to control potassium.

Control vomiting and nausea with antiemetics.

Treat pyelonephritis (kidney infection) with antibiotics.

Administer forced nutrition in anorexic cats.

Perform peritoneal dialysis or hemodialysis in cases of severe impairment of renal function.

On the other hand, the treatment of chronic kidney disease should include the following therapy:

Control of proteinuria with angiotensin-converting enzyme (ACE) inhibitors (benazepril or enalapril).

Restriction of phosphate in the diet or use of phosphate binders, and use of renal diet in advanced stages.

Forced nutrition in anorexic cats.

Treatment of hypertension with amlodipine.

Potassium supplements in advanced stages and cats with little phosphorus.

Treatment of severe anemia with erythropoietin.

Control of dehydration with fluid therapy.

Feline infectious peritonitis

Feline infectious peritonitis is of the most contagious diseases of the cat, the most deadly, and the one with the worst prognosis. It is a fatal disease in almost all cases, with no effective market treatment. It is caused by the feline enteric coronavirus when it mutates, which happens in around 20% of cats infected with this intestinal virus. When this mutation occurs, the virus does not remain only in the intestine but also can infect macrophages and monocytes, which are cells of the immune system and are distributed throughout the body.

Depending on the competence of the cat's cellular immune system, the disease may not occur; it may produce a dry form with the formation of pus granulomas in organs, compromising their suitable functionality, or a wet form, which is much more serious and rapid in the effusions of fluid form in the abdominal and/or thoracic cavity of the affected cat.


There is no treatment for this virus, and the outcome is usually fatal. Still, symptomatic treatment should always be attempted with a protein-rich diet, use of proteolytic enzymes, vitamin complexes, drainage of effusions in wet PIF, use of corticosteroids to suppress the immune system humoral and reduce consequences at the vascular level, use of cellular system enhancers such as feline recombinant omega interferon or dexamethasone injection in cavities so that the spill does not occur.

In recent years, two active ingredients have been studied that seem to have a good chance of being an effective treatment for FIP: the 3C protease inhibitor GC376 and the nucleoside analog GS-441524, the latter appearing to be more promising. However, as we say, they are still being studied.


Although it is not frequent, the rabies virus is deadly for cats, thanks to vaccination. It also can be one of the cat diseases transmissible to humans. Rabies is a very important fatal zoonosis for humanity; cats can suffer from it and transmit it to humans. The virus is transmitted from the saliva after the bite of an infected animal. It goes to the central nervous system, causing flaccid paralysis due to a lower motor neuron syndrome that evolves into the upper and cortex, causing encephalitis and ends up causing death.


All rabies infections culminate in death, and for animals, including cats, treatment is prohibited, always performing euthanasia due to the significant public health risk that it poses as it has the power of transmission to humans and other animals.

As we can see, these deadly diseases in cats often have no specific treatment, so preventive medicine becomes the best option to avoid them or at least diagnose them as soon as possible.

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