Cytauxzoonosis (Bobcat Fever)

Cytauxzoonosis is one of the most feared infectious diseases of cats in the regions where it occurs, precisely because it is so aggressive. It is caused by Cytauxzoon felis, a microscopic blood parasite carried by ticks and maintained in the wild by bobcats, which typically survive infection and act as a reservoir. When an infected tick feeds on a domestic cat, it passes the parasite into the bloodstream, and from there the illness unfolds with alarming speed.

Inside the cat, the parasite first multiplies within cells lining the blood vessels, particularly in the lungs, liver, spleen and lymph nodes, where growing clusters physically obstruct blood flow to vital organs. It then invades the red blood cells. The result is a sudden, overwhelming illness: a spiking fever, profound weakness, refusal to eat, difficulty breathing, jaundice and, without rapid treatment, collapse and death often within about a week of the first signs.

Diagnosis rests on finding the parasite in blood smears or tissue samples, sometimes confirmed with specialised testing, against a background of the cat’s history and season. Treatment is intensive and must begin as early as possible: the atovaquone-and-azithromycin combination together with round-the-clock supportive care offers the best chance, yet survival remains uncertain and recovered cats may carry the organism afterwards. All of this is why the emphasis falls so heavily on prevention — diligent, year-round-appropriate tick control and limiting a cat’s exposure to tick habitat are far more reliable than any cure. Owners in endemic areas should treat sudden fever and lethargy in an outdoor cat as a genuine emergency.