Babesia are malaria-like protozoans that parasitize and reproduce within mammalian red blood cell.  Although primarily transmitted by tick bite, babesiosis can also be acquired via blood transfusion and maternal-fetal transmission.

 

The first Babesia species was discovered in 1888 by Victor Babes, a Hungarian pathologist in whose honor the organisms were subsequently named. Over 100 distinct species have since been identified within the Babesia genus, despite there being 20+known forms to date known to infect humans, current testing only looks for two of them.

 

Clinically, babesiosis appears to have a wide spectrum of disease severity. Most patients experience a viral-like illness that can last weeks to months but which usually resolves fully. A significant minority of patients are entirely asymptomatic. In patients with a complicating condition, however – such as underlying immunosuppression – the disease course can be severe and potentially fatal. Some species of Babesia, such as B. divergens, appear to be more virulent than others.