Babesiosis in Cats
Babesiosis is the diseased state caused by the protozoal (single celled) parasites of the genus Babesia. The most common mode of transmission is by tick bite, as the Babesia parasite uses the tick as a reservoir to reach host mammals. Infection in a cat may occur by tick transmission, direct transmission via blood transfer from dog or cat bites, blood transfusions, or transplacental transmission. The incubation period averages about two weeks, but symptoms may remain mild and some cases are not diagnosed for months to years. Piroplasms infect and replicate in the red blood cells, resulting in both direct and immune-mediated hemolytic anemia, where the red blood cells (RBCs) are broken down through hemolysis (destruction) and hemoglobin is released into the body. This release of hemoglobin can lead to jaundice, and to anemia when the body cannot produce enough new red blood cells to replace the ones being destroyed. Immune-mediated hemolytic anemia is likely to be more clinically important than parasite-induced RBC destruction, since the severity of the condition does not depend on the degree of parasitemia.
Cats that spend time outdoors are more susceptible to tick bites, putting them at higher risk for this infection. This is especially so during the summer months from May to September, when tick populations are at their highest. Being vigilant about tick avoidance and removal is the best method for preventing the onset of Babesiosis.
- B. felis — small (2–5 µm) piroplasm that infects cats; reported in Africa
- Cytauxzoon felis— small piroplasm that infects cats; reported in the U.S.
Symptoms and Types
- Lack of energy
- Lack of appetite
- Pale mucous membranes
- Icterus
Causes
- Background history of tick attachment
- Immune suppression may cause clinical signs and increased parasitemia (parasite infection in the blood) in chronically infected cats
- History of a recent animal-bite wound
- Recent blood transfusion
Diagnosis
You will need to give a thorough history of your cat's health, including a background history of symptoms, and possible incidents that might have precipitated this condition. Your veterinarian will perform a complete physical exam on your cat. A blood chemical profile, a complete blood count, a urinalysis and an electrolyte panel will be conducted.
Your veterinarian may use a Wright’s stain to stain a blood sample for microscopic examination, since this will allow for your doctor to distinguish blood cells, making an infection of the blood more readily apparent. Immunofluorescent antibody (IFA) tests for antibodies in the serum that react with Babesia organisms may also be performed. Cross-reactive antibodies can prevent the differentiation of species and subspecies. However, some infected animals, particularly young cats, may have no detectable antibodies.
PCR (polymerase chain reaction) tests for the presence of Babesia DNA in a biological sample can differentiate subspecies and species and are more sensitive than microscopy.
Treatment
Most patients can be treated on an outpatient basis, but severely ill patients, especially those requiring fluid therapy or blood transfusions, should be hospitalized.
Living and Management
Your veterinarian will want to monitor your cat's progress, and will schedule follow-up appointments to repeat blood chemical profiles, complete blood counts, urinalyses and electrolyte panels. Two to three consecutive negative PCR tests beginning two months post-treatment should be performed to rule out treatment failure and persistent parasitemia.
If your cat is spending time in an area that is a known tick habitat, prevention is the best course of action. Check your cat daily for the presence of ticks and remove them promptly. The longer a tick stays on the body, the more likely the transmission of the parasite is to occur.