Babesia parasites inside red blood cell, computer illustration. This is the classic tetrad-form, or Maltese cross formation, of Babesia merozoites inside a red blood cell. Several Babesia species cause malaria-like diseases in humans and livestock. The infectious stage of babesia is the sporotoite, which is transmitted via tick bites. It enters an erythrocyte (red blood cell) and undergoes asexual reproduction producing merozoites, whose presence inside a red blood cell is used for laboratory diagnosis of babesiosis.