Experimental transmission of Babesia microti infection by the oral route.

Previously we have described the transmission of malaria by the oral route in a murine model. Due to the similarities between Plasmodium and Babesia, we tried to reproduce oral transmission in parasites of the latter genus by ingestion of infected blood and by cannibalism. In the first case, experimental mice were inoculated orally with 20, 50, or 100 microliters of Babesia microti-infected blood, and in the second, each fasted experimental mouse was offered the corpse of an infected mouse serving as the bait inoculum. B. microti infection was acquired by 3.7% of all experimental animals orally inoculated with infected blood and by 15.1% of all mice inoculated by cannibalism. The approximate period of prepatency ran from 2 to 4 weeks. No control mouse acquired the infection. This represents the first time that oral transmission of babesiosis has been described. This kind of transmission may be present in nature. Babesiosis may be acquired and maintained in nature in the absence of ticks.