
Feline leukemia virus (FeLV) is a life-threatening disease that can affect any cat. It's something every pet owner should be concerned about, also because it's a leading cause of infectious death in cats.

In this blog, we'll discover everything there is to know about this virus and why we should vaccinate our cats from it.
What Is FeLV?
Feline leukemia is caused by a retrovirus that attacks the immune system, suppressing it and weakening the cat's defenses. Once weakened, the cat becomes vulnerable to other types of infections and diseases. In other words, more problems.
It starts with transmission. Once a cat has it, the virus disrupts normal cell function by inserting its own genetic material into the cat’s DNA. When this happens, immunosuppression, anemia, and even certain types of cancer come into play.
How Is FeLV Transmitted?
What makes FeLV particularly concerning is how easily it can infect cats. Here’s how the virus spreads:
Saliva and Nasal Secretions
The primary mode of transmission is saliva and nasal secretions. This means that close interactions such as fighting, mating, and grooming can spread the virus from cat to cat. This also applies to objects shared by cats, such as food and water bowls.
Blood, Urine, and Feces
Though less common, FeLV can be transmitted through blood. Cats that engage in fights, particularly outdoor or feral cats, can transfer the virus when infected blood gets into wounds.
Shared litter boxes can pose a risk if cats come into contact with the urine or feces of an infected cat. While this mode of transmission is rarer, it is still possible, especially in unclean or overcrowded environments.
Birth and Nursing
Pregnant cats with FeLV can also pass the virus to their kittens, a method of transmission called vertical transmission. After birth, kittens can also get infected through nursing if the virus is present in an infected mother’s milk.
Plus, kittens have underdeveloped immune systems. As a result, they are more susceptible to the virus and the disease it causes. This often progresses to active infection more quickly than in adult cats.
What Are the Symptoms of Feline Leukemia?

The suppression of the immune system means that the infected cats can experience a wide range of symptoms. This includes:
General Signs. Many FeLV-positive cats initially show non-specific signs of illness. These include lethargy, loss of appetite, fever, and weight loss.
Anemia. Anemia is one of the most common and serious effects of FeLV. Signs include pale gums and tongue, chronic fatigue, and labored breathing.
Secondary Infections. Secondary and recurrent infections are also signs of a suppressed immune system. This can appear on the skin, respiratory system, or urinary tract.
Cancer and Tumors. FeLV is closely associated with the development of certain cancers, such as lymphomas.
Digestive Issues. A FeLV infection can also cause gastrointestinal distress, leading to chronic vomiting and diarrhea.
Behavioral Changes. Behavioral changes and shifts can be clear in affected cats because of the constant pain and discomfort they feel. Some will be irritable, while others will rather hide and rest.
Neurological Symptoms. FeLV can affect the nervous system, leading to seizures, ataxia, and behavioral changes.
Frequently Asked Questions
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