Cytauxzoonosis

What Is Cytauxzoonosis?

Cytauxzoonosis, often called bobcat fever, is a serious blood-parasite infection of cats caused by Cytauxzoon felis. Ticks pick up the parasite from bobcats, which usually carry it without getting sick, and then pass it to domestic cats when they bite. The parasite invades white blood cells and red blood cells and can block small blood vessels, leading to rapid, life-threatening illness.

In the United States, cases cluster in the South-Central, Southeastern, and Mid-Atlantic states, including Missouri, Arkansas, Oklahoma, Tennessee, Kentucky, Georgia, and the Carolinas. The lone star tick and the American dog tick are the main carriers, so most infections happen from spring through early fall in cats that spend time outdoors near wooded areas. Dogs do not get this disease.

Signs Owners Notice

• Sudden lethargy, hiding, and refusal to eat
• High fever, sometimes followed by a dangerously low temperature late in the disease
• Yellow gums, eyes, or skin (jaundice) and pale gums from anemia
• Fast or labored breathing
• Crying out in pain, weakness, collapse, or seizures in advanced cases

Causes and Risk

Cats become infected only through a bite from an infected tick; the disease does not spread directly from cat to cat. Risk is highest for outdoor or indoor-outdoor cats living near bobcat habitat in endemic regions. Signs usually appear one to three weeks after the tick bite. Some cats in endemic areas survive and become carriers, which shows the disease is not always fatal, but it remains one of the most dangerous tick-borne infections in pets.

Diagnosis

Vets often suspect cytauxzoonosis from the history (outdoor cat, endemic area, warm season) combined with fever, jaundice, and low blood cell counts. A blood smear examined under the microscope can show the parasite inside red blood cells, and PCR testing confirms the infection. Blood work also checks for anemia, low platelets, and liver involvement, and helps distinguish it from other causes of anemia like immune-mediated hemolytic anemia.

Treatment and Outlook

• Antiparasitic medication: a combination of atovaquone and azithromycin is the most widely used treatment.
• Intensive supportive care: IV fluids, oxygen, pain control, a feeding tube, and blood transfusions when needed, usually in hospital.
• Close monitoring: the first several days are the most critical.

Even with treatment, many cats do not survive, though outcomes have improved with modern protocols and early care. Cats that recover usually return to normal health. Hospitalization costs in the US can run from a couple of thousand dollars upward, depending on how long intensive care is needed.

Practical Tips for US Pet Owners

• Keep cats indoors, especially during tick season, if you live in an endemic state.
• Use a veterinarian-recommended tick preventive labeled for cats year-round or through tick season. Never use dog-only flea and tick products on cats, as some are toxic to them.
• Check outdoor cats for ticks daily, particularly around the head, neck, and ears.
• Find a nearby practice through veterinary clinic listings.

Key Takeaways

• Cytauxzoonosis is a tick-borne parasite infection of cats carried by bobcats.
• It progresses fast and is often fatal without immediate intensive care.
• Indoor living and cat-safe tick prevention are the best protection.

FAQ

Can my cat catch bobcat fever from another cat?
No. It spreads through tick bites, not direct contact between cats.

Can dogs or people get cytauxzoonosis?
No. Cytauxzoon felis affects cats; dogs and people are not known to become sick from it.

Is there a vaccine?
There is no commercially available vaccine, so tick prevention and keeping cats indoors are the main defenses.