CYTAUXZOONOSIS IN THE CAT
THIS CONDITION IS CONSIDERED UNIFORMLY FATAL IN THE DOMESTIC CAT
HOW DO CATS GET THIS INFECTION?
Cytauxzoon felis is spread by tick bites. The usually implicated tick is the American Dog Tick (Dermacentor variabilis). Bobcats carry the Cytauxzoon piroplasms in their blood, ticks feed on the bobcats, and then drop off and molt to their next life stage. They are still carrying the Cytauxzoon piroplasm when they attach onto their next host and if that next host is a domestic cat, a lethal infection results.
American Dog Tick (Dermacentor variabilis)
CATS CANNOT BE INFECTED WITHOUT A TICK BITE.
HOW IS DIAGNOSIS MADE?
The cat typically has a fever with or without jaundice and is brought to the veterinarian for evaluation. In most cases the piroplasms are fairly obvious when the blood sample is evaluated. Because the tissue phase of the infection with the schizonts comes first and the blood infection with piroplasms comes after, it is possible that at the time the blood is tested no piroplasms are yet present. Because of the rapid progression of the infection, piroplasms will likely be present in a few days if they are not present at first so sometimes a second blood evaluation is needed.
Because piroplasms sometimes have variable sizes, they are sometimes mistaken for Mycoplasma hemofelis, a much more treatable infection. Cytauxzoon organisms are larger and have a thick “dot” on their ring-shape.
If diagnosis is to be made post-mortem it is usually easy to find the schizonts in many body tissues.
IS THERE ANY TREATMENT AT ALL?
In one study diminazine aceturate treatment was able to save several cats in one study. Another study has reported success in one cat using imidocarb diproprionate. Cats must be hospitalized and their blood anti-coagulated so as to prevent inappropriate clotting and vessel clogging with schizont-laden macrophages.
A milder strain of Cytauxzoon felis seems to have emerged in west Arkansas and east Oklahoma where a number of cats have survived without treatment (as do most bobcats). These cats continue to have piroplasms in their blood but seem to have no effect from this.
The most effective prevention is to keep the cat indoors where there is no tick exposure. The next best prevention is to use a tick control product on the cat and there is one currently marketed: Frontline. It is important to realize that most canine tick products are toxic to cats and cannot be safely used.
Page posted: 12/20/07