Vector Borne Diseases Part 4: Cytauxzoonosis

Cytauxzoon or "bobcat fever" is a disease limited to cats.  Cytauxzoon felis is a blood parasite carried by ticks (many species have been implicated).  The natural reservoir for Cytauxzoon is the bobcat (who are asymptomatic carriers) and disease prevalence is limited to the natural range of the bobcat.

Bobcat habitat

The cytauxzoon life cycle in a domestic cat includes both a blood phase and a tissue phase.  It is the tissue phase that causes the most problems.  The body recognizes the organism as foreign and attacks it aggressively.  The "clean-up" cells become so numerous and are so full of organism that they plug blood vessels leading to multisystemic disease.  The course of disease is short, with death often occurring in untreated cats within 5 days from the onset of clinical signs.

Upon presentation cats usually have a high fever, pale mucous membranes, depression, lethargy, anorexia, and icterus.  Lab work indicates anemia, low platelets, increased bilirubin and liver enzymes.  Diagnosis is suspected based on clinical signs, and history of tick exposure in an endemic area.  Recognition of organisms in the red blood cells evaluated under a microscope is definitive as is finding the tissue stage on needle biopsies (aspirates) of spleen, liver, lymph node, or bone marrow.  There is also a PCR test available.

Cytauxzoon felis in red blood cells

At the time I graduated from veterinary school this disease was considered uniformly fatal.  But now, there is hope.  At one point a drug called Imidocarb gave a survival rate of 27%.  More recently a combination of Azithromycin and Atovaquone have provided a 60% survival rate.  Owners should be forewarned though-this is by no means a guarantee of survival, the drugs are not inexpensive and ancillary treatments such as blood transfusions, feeding tube placement and several days of hospitalization might be required.

Prevention is routine use of tick prevention and keeping cats indoors.

This disease does not affect dogs or people and cannot be directly transmitted between cats, only via tick bites.