Winn Feline Foundation Progress Report
By Susan Little DVM, Diplomate ABVP (Feline)
Isolation and Characterization of Ehrlichia species Infecting Cats
Investigators: Michael Lappin, Cynthia Stubbs
Colorado State University
Ehrlichia species are members of the Rickettsial family and are microorganisms that live inside cells. Various forms of this organism infect different animals. For example, E. canis infects dogs and related species. Although disease from Ehrlichia infection is considered uncommon in cats, evidence of infection has been documented around the world. In most species, ticks play a role in transmission. In cats, however, the route of transmission is not yet known.
The most common clinical signs associated with ehrlichiosis in cats are fever, loss of appetite, weight loss and depression. The most common laboratory finding is anemia. Diagnosis of ehrlichiosis in cats is usually made by finding groups of the organism called morulae inside white blood cells. The morulae are hard to find, however, and other more sensitive tests for this organism, such as polymerase chain reaction (PCR), are not widely available. Even though many cats carry antibodies to Ehrlichia species, very few of them become ill, so diagnosis cannot be based on a positive antibody titer alone. Diagnosis is therefore often based on a combination of appropriate clinical signs, ruling out other possible diseases, finding antibodies to Ehrlichia, and response to treatment with drugs such as enrofloxacin or doxycycline.
The researchers evaluated blood samples from three cats in the United States suspected to have ehrlichiosis using a PCR test. All three cats were positive. Using primers specific for Ehrlichia equi, the species that causes ehrlichiosis in horses, it was found that all three cats were infected with this Ehrlichia species. All cats responded to treatment with either enrofloxacin or doxycycline. This work adds to the body of knowledge about ehrlichial infections in cats and provides veterinarians with another possible cause of illness for cats with anemia and fever.
For more information:
Lappin, M.R. et al. (2002) Ehrlichia equi infection of cats of the United States (abstract). Proc 20th Amer Coll Vet Intern Med Forum, Dallas, TX.