Tick transmission of Babesia microti to rhesus monkeys (Macaca mulatta)

To determine whether Ixodes dammini is capable of transmitting Babesia microti to primates, infected nymphal ticks were allowed to feed on five Macaca mulatta. The monkeys were then followed for at least 60 days with daily thick blood smears for evidence of infection. Patent B. microti parasitemia developed in four of the five animals. Prepatent periods were 13, 18, 20, and 28 days. Maximum parasitemia ranged from 83 to 7,068 organisms/mm3 blood. Splenectomy 15-17 months after exposure to ticks results in recurrences of parasitemia in three of the four infected monkeys.