Cytauxzoonosis in Cats

What is cytauxzoonosis?

Cytauxzoonosis is a tick-borne parasitic disease caused by a single-celled organism called Cytauxzoon felis. This organism infects cats’ blood cells. It was first reported in the USA in 1976 and is now an important emerging disease in domestic cats. 

How do cats become infected with this parasite?

The parasite’s natural host is the bobcat, but the parasite can infect all members of the cat family, both wild and domestic. While most bobcats show no obvious signs of illness, infected bobcats become persistent carriers of the disease. The infection is spread to other cats through a tick bite. Many species of ticks may bite cats, but the only species shown to transmit the infection are the Lone Star tick and the American dog tick. Cats cannot catch the infection directly from an infected cat or from eating a tick.

Is my cat at risk of becoming infected?

Currently, this infection is found in areas in the central, south-central, south-eastern, and mid-Atlantic regions of the United States, but the range of the ticks capable of spreading this disease has been expanding due to climate change and resulting local weather changes. Outdoor cats or cats that live in homes with other pets that go outdoors are at a greater risk of becoming infected. Habitats that are densely wooded or are naturalized are more likely to support populations of bobcats and ticks. Most infections occur in the months between spring and fall when ticks are most active.

What are the clinical signs of cytauxzoonosis?

Clinical signs of cytauxzoonosis usually develop about 10 days after a tick bite. The initial signs of this disease are vague and non-specific, making diagnosis difficult. Early signs include:

• Lack of energy
• Lack of appetite
• Difficulty breathing
• Pale gums

On physical examination, many infected cats will have the following signs:

• Dehydration
• Anemia (low red blood cell count)
• Jaundice (yellow gums or yellow whites of the eyes)
• Fever
• Increased heart rate
• Increased respiratory rate
• Enlarged lymph nodes, spleen, or liver 

Infected cats may appear to be in pain and may not want to be touched. As the parasites multiply within the blood, they are carried throughout the body and can infect many organs. The disease progresses quickly if left untreated, with death possible in two to three days after the spike in fever. In the later stages of infection, a cat may become hypothermic (low body temperature), may develop seizures, or may lapse into a coma.

How is cytauxzoonosis diagnosed?

• Physical examination: Finding a tick on your cat may help with the diagnosis, but cats often groom ticks away before they show signs of illness.
• Complete blood count (CBC): A complete blood count will show decreased numbers of red blood cells, white blood cells, and platelets.
• Blood smear: Examination of a blood smear may reveal C. felis organisms within red blood cells or certain white blood cells. However, in the early stages of the disease, there may be no organisms present in the blood.
• Biochemistry: These tests will reflect which organs are involved with the disease.
• Fine needle aspiration: If the spleen or liver feels enlarged, your veterinarian may recommend a fine needle aspiration to obtain samples of cells and tissues for laboratory analysis. If C. felis organisms are identified in the sample, the diagnosis is confirmed.
• PCR test: A diagnostic PCR test can detect the DNA of the parasite. 
  

How is cytauxzoonosis treated?

In most cases, hospitalization is necessary so the cat can receive supportive treatments such as intravenous fluids, blood transfusions, and drug injections. In some cases, your cat may require a feeding tube for nutritional support. Recovery may take up to a week of hospitalization. Specific drug protocols include anti-protozoal drugs such as imidocarb or a combination of atovaquone and azithromycin (an antibiotic).

What is the prognosis?

When cytauxzoonosis was first identified in cats, it was inevitably fatal. However, as awareness of this disease has increased, diagnosis and treatments have improved. Veterinarians are diagnosing it earlier and somewhat effective drug treatments have been identified. The current survival rate is about 60% with early diagnosis and treatment. It is possible that there are different strains of cytauxzoonosis that vary in their severity, with some strains causing less severe disease. 

Cats that survive infection usually have a full clinical recovery within a few weeks but may remain persistently infected and act as a reservoir for infection. Cats that recover from this disease should be kept indoors so they are not a source of infection to other cats.

How can I prevent my cat from getting infected?

The most effective way to prevent cytauxzoonosis is to prevent tick exposure. Ensure your cat is protected with an effective, veterinarian-recommended tick preventive, especially if they spend any time outdoors. Since no preventive is 100% effective, the best prevention needs to include keeping your cat indoors or at least away from areas likely to be infested with ticks.

If you find a tick on your cat, remove it as soon as possible. Wear disposable gloves and grasp the tick with fine tweezers near your cat's skin. Firmly, but slowly, pull it straight out.

There are also useful tools available called Tick Twisters or Tick Keys. However, use them cautiously, as twisting or jerking the tick may cause the mouthparts to break off and remain in the skin. If you are unable to remove the tick or are unsure of how to do so, contact your veterinarian.

Can people get cytauxzoonosis?

C. felis infection is limited to members of the cat family and poses no risk to humans, dogs, or other species of animals.