Babesiosis of companion animals and man.

Babesiosis is caused by numerous organisms and is seen in a wide range of vertebrate hosts. The spectrum of disease is broad and ranges from asymptomatic carrier states to fulminant disease that results in rapid death. The importance of babesiosis in companion animals is well-recognized in parts of the world where virulent strains exist and where the diagnosis and treatment of both typical and atypical presentations is part of the everyday course of events for the small animal clinician. In parts of the world such as the United States where less virulent strains are found, diagnosis is more difficult. Diagnosis requires an astute eye examining the blood smear and a keen mind willing to "consider the zebras without forgetting the horses." Babesiosis is not uncommon in the United States; it is merely uncommonly diagnosed. The small animal clinician needs to be aware of the disease and its myriad possible presentations. A clearer understanding of the disease will lead to a truer picture of its importance not only in the United States but also worldwide.