Mild disease is mainly an extravascular hemolytic anemia but severely affected dogs have signs of intravascular hemolysis (as the parasite lyses the red blood cell to complete its lifecycle) and may develop DIC. In general, the parasite induces a concurrent Coombs positive IHA. A hyperacute syndrome producing hypotensive shock has been seen in some dogs, and also occurs with B. bovis. This is thought to be due to liberation of kallikrein (a potent vasodilator) and is usually associated with low parasite numbers. Some dogs have a chronic syndrome of anemia and fever with lymphoid hyperplasia and lymphocytosis; parasitemia is very difficult to detect in chronic cases. Dual or triple infections with other tick-borne rickettsial organisms (Mycoplasma, Ehrlichia) can be seen in some dogs. Definitive diagnosis is based upon finding the organisms in red cells or on a positive indirect fluorescent antibody result. B. canis appear usually as single or multiple pear-shaped organisms. B. gibsoni, which is much less common in the U.S. than B. canis, is smaller than B. canis and more likely to escape recognition even when present. Red cells containing Babesia organisms have a density similar to that of reticulocytes, and therefore, are concentrated just below the leukocytes in a centrifuged microhematocrit tube. Low-grade parasitemia is more easily detected by examination of a buffy coat smear than by examining a blood smear, especially if collected from peripheral blood vessels, such as from the ear. Babesia organisms are removed from peripheral red blood cells in the spleen, resulting in asymptomatic carriers. As Babesia is endemic in Greyhounds, many blood donors are splenectomized or treated with immunosuppressive doses of corticosteroids to detect subclinical infections. Babesia felis is a rare parasite that can produce a regenerative anemia, lethargy and anorexia in cats. The parasite is very small and quite difficult to visualize. Affected cats can be icteric and hyperglobulinemic. Babesia equi causes a hemolytic anemia in acute cases. Affected animals often become asymptomatic carriers. The organism is transmitted by Dermacentor ticks. Four pyriform organisms are typically seen in infected red blood cells, forming a "Maltese cross". Other clinical signs associated with Babesiosis (or piroplasmosis) are fever, edema, icterus and leukopenia. Babesia bigemina (Texas cattle fever) and Babesia bovis (red water fever) affect cattle. B. bovis produces more severe disease and can cause red water fever in deer. They are transmitted by Boophilus ticks. They produce a hemolytic anemia, hemoglobinuria, fever, and anorexia. The hemoglobinuria in Babesiosis distinguishes the hemolytic anemia from Anaplasmosis, which is an extravascular hemolysis. Young calves < 7 months of age are often resistant to infection. B. bovis, in particular, can induce DIC and can cause autoagglutination of red blood cells in the brain which blocks capillaries, producing cerebral babesiosis. Diagnosis is by detection of the organism in blood smears or by serology (IFA or complement fixation). Babesia ovis and Babesia motasi infect sheep. B. ovis produces mild disease of short duration, whereas B. motasi causes fatal disease in acute cases. Like all Babesia organisms, sheep that recover from babesiosis become asymptomatic carriers. |
