We see relatively few blood parasites in cats.
Cytauxzoon felis is a microscopic red blood cell parasite that infects cats. This is mostly a problem in the south-central part of the USA . It is generally fatal within a few days of the onset of illness. Transmission is via Dermacentor ticks (or blood transfusions). Signs include lethargy, fever, loss of appetite, weight loss, vomiting, dehydration and jaundice. Sub-clinical disease exists as well—these cats look just fine. It is thought that this is because they have a less nasty strain of the parasite. Diagnosis is made by running blood tests. Treatment involves fixing the anemia and dehydration, and anti-parasitic drugs may be prescribed by your veterinarian.
Feline Infectious Anemia
This condition is caused by Mycoplasma haemofelis and Mycoplasma haemominutum, formerly called Haemobartonella felis. These organisms parasitize the red blood cells causing to them burst, producing severe anemia (shortage of red cells). These mycoplasma are cell-wall deficient bacteria-like organisms, rather than true parasites. If both of these subtypes of organism are present, the disease is even more severe than usual. The disease is most commonly spread by lice and fleas. Signs may be absent, mild or severe (fever, depression, pale membranes, loss of appetite, and even death). Blood tests taken by your veterinarian will help confirm the diagnosis. Treatment involves antibiotics and possibly steroids, intravenous fluids and blood transfusions. Animals may remain carriers for life, but rarely exhibit signs of disease more than once.