• Feline leukemia and rabies are contagious, untreatable, and commonly fatal.
  • Cats that go outside are at increased risk for exposure to feline leukemia and rabies.
  • Vaccination can protect cats from disease associated with the feline leukemia and rabies viruses.

What Are Feline Leukemia and Rabies?

Feline leukemia virus (FeLV) is contagious among cats. Unlike many other viruses that enter specific cells in the body and destroy them, FeLV enters certain cells in a cat’s body and changes the cells’ genetic characteristics. This permits FeLV to continue reproducing within the cat each time infected cells divide. This allows FeLV to become dormant (inactive) in some cats, making disease transmission and prognosis (outlook) difficult to predict.

Rabies virus is dangerous and infects animals and humans worldwide. Rabies is generally fatal in all species, and any warm-blooded animal can become infected. Foxes, skunks, coyotes, and certain rodents spread the disease in many cases. Surprisingly, cats are more commonly involved in spreading rabies than dogs are. In fact, cats are the number-one domestic animal carrier of rabies in the United States.

How Do Cats Become Infected With Feline Leukemia and Rabies?

Feline leukemia is generally transmitted through contact with saliva from an infected cat. Certain “social” behaviors such as mutual grooming and sharing food or water bowls can spread the disease. Kittens can become infected during fetal development or during the first days of life as their mothers nurse and care for them.

FeLV is killed by many disinfectants and does not live for very long in the environment, so contact with an infected cat is necessary for disease spread. However, predicting which cats can transmit the disease is complicated because some cats that are contagious don’t develop signs of infection.

Like FeLV, rabies is also transmitted through contact with saliva from an infected animal. With rabies, however, the most common means of saliva contact is through bite wounds. Cats that go outside, fight with other cats, or encounter wild animals are at increased risk for exposure to rabies.

Signs of Feline Leukemia and Rabies

Not every cat that becomes infected with FeLV develops clinical signs. The immune system of some cats can eliminate the infection before the cat becomes sick. In other cats, the virus can “hide” in the bone marrow, where it is difficult to detect until it begins to cause problems later in life. Other cats become carriers of the disease or experience various illnesses before eventually dying of FeLV-associated complications. Because FeLV can affect almost any organ system in the body, clinical signs can vary significantly. Signs include:

  • Anemia (lack of red blood cells)
  • Leukemia
  • Immune suppression
  • Fever
  • Lethargy (tiredness)
  • Chronic respiratory infections
  • Chronic dental and gum infections
  • Cancer of the lymphatic system (and other cancers)

The clinical signs of rabies can be vague and difficult to identify. The virus is usually introduced into the body through a bite wound from an infected animal. After entering the body, the rabies virus makes its way into the nervous system and then into the salivary glands (glands in the neck that produce saliva). Once the virus enters the salivary glands, the animal can pass the infection to other animals and humans through saliva. The incubation period associated with rabies can be as brief as a few days or as long as several months. Death can occur from respiratory failure, seizures, or other complications. Unfortunately, early clinical signs may not be apparent before the animal becomes infective, which means that an infected cat can spread the disease before it shows signs of being sick. Clinical signs of rabies progress through several stages, and not all infected cats show evidence of all stages:

  • Early signs: Fever, acting nervous or agitated, hiding
  • Later signs: Aggression, increased agitation, erratic behavior
  • End stage: Muscle weakness and paralysis, coma, death

Diagnosis and Treatment

Because there are several stages of FeLV infection and cats can handle the infection differently, diagnosis is not always straightforward. Blood tests detect the disease in many cats, but for other cats, the bone marrow must be examined to confirm infection. Some cats may test positive on blood tests when they are young kittens but test negative later on if their immune system has been able to eliminate the infection. Similarly, some cats may test negative at one point and test positive later on as the virus progresses through various stages in the body. Because FeLV can have many clinical presentations, your veterinarian may want to test your cat if it seems to be ill—especially if a fever is present. Some cats need to have multiple tests done to confirm infection.

No medication can eliminate FeLV. Most treatments are aimed at managing the clinical signs and complications. Therapy may include blood transfusions, intravenous fluids and feedings, chemotherapy, and antibiotics.

The tests used to confirm a diagnosis of rabies are performed by examining and testing the brain after the animal has died or been euthanized. Unfortunately, there are no diagnostic tests considered accurate enough to confirm rabies in a living animal. As with FeLV infection, there are no effective treatments for rabies in animals. Because of the high fatality rate associated with rabies, the best way to protect your cat is to minimize exposure to animals that may transmit the infection and keep your cat’s rabies vaccination up to date.

Vaccination and Prevention

Several vaccines are available for preventing disease associated with FeLV infection and rabies. Some of the available FeLV vaccines are combination vaccines that also protect against feline herpesvirus, panleukopenia (feline distemper), and calicivirus. Available rabies vaccines may be single-organism vaccines or combination formulations that protect against other feline viruses. All of the available FeLV and rabies vaccines have been tested and found to be safe and effective when administered as directed.

Kittens are generally vaccinated against FeLV around 8 to 9 weeks of age. A booster vaccination is given 3 to 4 weeks later, followed by boosters each year as long as the risk for exposure remains. If risk for exposure is low, your veterinarian may not recommend the FeLV vaccine for your cat. Initial rabies vaccinations are generally given to kittens between 12 and 16 weeks of age. A booster vaccination is given a year later. Depending on which rabies vaccine is used, subsequent boosters may be given every 1 to 3 years.

Some municipalities have regulations mandating that cats receive vaccinations against rabies. Vaccination against FeLV is not required by law but is highly recommended for cats at risk for exposure to the virus. Cats that go outside or live with other cats are at greater risk for exposure to FeLV compared with cats that stay indoors and have limited contact with other cats. Similarly, cats that go outside where they can encounter stray or wild animals are at greater risk for exposure to rabies. Ask your veterinarian about how to protect your cat from these infectious diseases.

Because FeLV is transmitted through contact, keeping sick cats separated from healthy cats can reduce the likelihood of transmission. Any new kitten or cat being introduced into the home should be examined by a veterinarian as soon as possible and separated from all other household pets for a quarantine period of at least a few weeks. During that time, the new cat should be tested for FeLV and monitored closely for any signs of illness. Any problems should be reported to your veterinarian before introducing the new cat to your other pets.

Feline leukemia is not considered contagious to humans. In contrast, rabies is contagious (and fatal) to any warm-blooded animal, including humans. If your cat is known or suspected to have either of these diseases, contact your veterinarian promptly to discuss how you can protect your other pets and family members.

This article has been reviewed by a Veterinarian.