Babesia is one of the most ubiquitous and widespread blood parasite in the world based on numbers and distribution of species in animals. The clinical presentation may vary according to the incriminated species. In some states of the USA this kind of infection is endemic; the number of cases reported in Europe is inferior but more life-threatening. A better understanding of parasite specificities such as cycle and pathogenicity allowed to suggest treatment guidelines adapted to the different clinical and microbiological situations.