Cytauxzoon is a protozoal organism that is transmitted by ticks and causes big, big problems for cats. It is most commonly seen in cats who live in the south central and southeastern United States, although the range appears to be expanding.
Luckily for our canine friends, this is a condition that is only seen in cats. Both domestic cats and wild cats are prone, and bobcats are the reservoir for the disease. Bobcats usually only develop mild signs from cytauxzoonosis, but in our house cats, the disease is much more serious.
Ticks are infected with the protozoa when they bite a bobcat, and then they can transmit it to your cat when they bite her. The disease course is a little bit complicated, because the organism has two life stages. The most clinically relevant stage is the schizont. When Cytauxzoon organisms are transmitted to a house cat, the schizonts invade the lungs, spleen, liver, lungs, lymph nodes, bone marrow and other organs. This tissue invasion does not go unnoticed by the immune system, which mounts a rapid response. Immune cells called macrophages destroy and consume the schizonts with no problem. The trouble comes when lots of macrophages become so enlarged with schizonts that they clog the affected cat’s blood vessels. These blockages eventually cause cell death in every organ.
Clinical signs begin one to three weeks after infection. Cytauxzoonosis can be difficult to diagnose because clinical signs are non-specific. Decreased appetite, fever, lethargy and respiratory issues are common with cytauxzoonosis, but they also occur with any number of other conditions. Your veterinarian may be able to feel that your cat’s liver or spleen is enlarged, which could lead them closer to a diagnosis.
Blood samples can help with diagnosis. This is because the second phase of the organism lives in red blood cells. This stage is called the piroplasm. Piroplasms are ring shaped and can be seen in red blood cells under a microscope. However, piroplasms develop after schizonts, so cats who initially present with symptoms may not have piroplasms in their blood cells yet. The disease progresses rapidly, though, so they should be present within a few days of initial presentation.
Other confirmation tests can be performed, such as taking needle samples from affected organs (like lymph nodes or the liver) or by sending samples off for more sophisticated tests like PCR tests. However, the disease progression is so rapid that often there is not enough time to wait for test results. Cats with cytauxzoonosis will usually die within a week without treatment. As the disease progresses, central nervous system signs like seizures, confusion, or coma will occur.
Unfortunately, there is no therapy that has been proven to be effective. Cats with cytauxzoonosis are very sick and need aggressive supportive therapy. Hospitalization will be required for fluid therapy and possibly blood transfusions, which can be an expensive endeavor (unless, of course, you have pet insurance). There are two medications that have shown some promise in the treatment of cytauxzoonosis, but definitive proof of effectiveness has not been established.
Because of the danger of this tick-borne illness, prevention is key. Preventing ticks from biting your cat will prevent the transmission of disease 100% of the time. Ask your veterinarian for advice on which tick prevention is best for your feline best friend.