Cytauxzoonosis in Cats

Veterinarians became aware of the parasite and its ability to cause infections in house cats in the 1970s. Since that time, cases of cytauxzoonosis have gradually increased. The ticks that carry the parasite are often found in the southern and eastern United States, but can also be found rarely on the west coast. April through September are the months when ticks are most prevalent. 

The infection cannot spread from cat to cat or from mother to unborn kittens. The parasite is often found reproducing in the lymph nodes, liver, bone marrow, lungs or spleen, but can be present in other organs. Cytauxzoon felis lines the blood vessels and kills tissue cells in the organs. Some cats do survive the infection without treatment, however, this is not the norm.

The tick-borne parasite,Cytauxzoon felis, allows the infectious disease cytauxzoonosis to develop in all types of cat. The natural host of the parasite is the bobcat, however, house cats have an adverse reaction to the infection. The cat is exposed to the parasite when bit by a lone star tick carrying Cytauxzoon felis. The parasite is deposited through the wound created by the tick to feed on the cat. It can take 5-14 days for symptoms to start occurring in an infected cat. Cytauxzoonosis is a medical emergency, with many cats dying within two to three days after fever development if left untreated.

It may take one to two weeks after being exposed to the parasite for the cat to begin exhibiting symptoms. The first signs of infestation are usually the loss of appetite and the beginning of vocalizations of pain. All symptoms to watch for include:

• Pyrexia (increasing fever)
• Lethargy
• Depression
• Anorexia
• Dehydration
• Jaundice
• Enlarged lymph nodes
• Enlarged liver and spleen
• Hypothermia 
• Increased vocalization
• Fluid in the lungs (difficulty breathing)
• Anemia
• Coma

To become infected with cytauxzoonosis, a cat must come in contact with a lone star tick carrying the parasite Cytauxzoon felis. The ticks generally attach to the cat from low vegetation when the cat walks through. Areas where bobcats are known to live may carry more risk of disease exposure. Contributing factors include:

• Outdoor cats allowed to roam
• Cats who live near heavily wooded areas in rural settings

If any symptoms begin to develop in your cat, bring them into a veterinary clinic or animal hospital immediately. To make a proper diagnosis, the veterinarian will need to perform a complete physical examination of the cat. Blood tests will show indications of parasite presence. A complete blood count may reveal severe anemia and a biochemical profile will also show abnormalities and perhaps heightened liver enzyme concentration. 

Blood smears can be used to microscopically examine schizonts (a stage of Cytauxzoon felis) and identify them. Wright-Giemsa stains can clarify the visualization of microscopic organisms. When the schizonts or merozoites (the second stage of the parasite) are seen, they often are round or oval in shape. The veterinary professional will have to differentiate between Cytauxzoon felis and mycoplasma haemofelis (a parasite of the blood). Fine needle aspiration of affected organs may be used to gain samples for microscopic identification. A polymerase chain reaction (PCR) test can be used to identify the parasite through DNA samples. 

Finding the most effective treatment for cytauxzoonosis infection has taken years of trial and error. Emergency nursing can greatly contribute to a positive outcome for the cat.

Combination of Medications 

A joint prescription of atovaquone and azithromycin for the course of 10 days has shown to increase odds of survival by up to 64 percent. Hospitalization through this time may be needed to keep the cat in a stable state.

Supportive Care 

While the infection lasts in the cat, assisting the function of vital organs can give the cat enough strength to pull through. Intravenous fluids are administered to prevent and alleviate dehydration. A feeding tube may also be necessary to provide the cat with nutrients. Oxygen supplementation will be provided to assist the lungs. Heparin may be given to prevent the formation of blood clots. A blood transfusion may also be needed to give the cat higher levels of healthy blood. Anti-inflammatories may be given if fever does not begin to go down on its own. 

Fever should subside in five to seven days in cats that survive a cytauxzoonosis infection. All possible stress inducers should be removed from the cat at this time. Survival often leads to a complete recovery. Some cats may become a reservoir of the parasite for the rest of their lives. A check up appointment will be needed in two to three weeks’ time to take blood samples for testing. All blood work should come back normal at this point in recovery.

Giving your cat monthly, topical tick-prevention medication can help reduce incidents of Cytauxzoon felis exposure. This does not complete guard against infection. Only keeping your cat indoors at all times can prevent a tick from biting it.