Diagnosis
The confirmation of H. felis infection rests on the microscopic identification of the organisms on the surface of red blood cells on a blood smear. It is easy to confuse the organisms with other red blood cell changes. The presence of the organisms in an otherwise normal cat may be an incidental finding. The absence of the organism in an anemic cat does not rule out the disease, since their appearance in circulation appears to be cyclical. Furthermore, the parasites clear rapidly upon treatment with antibiotics, making detection difficult. Special laboratory stains may be helpful in identifying the organism microscopically. A sophisticated test called polymerase chain reaction, or PCR, may also help establish the diagnosis. This test looks for genetic material unique to H. felis.