ABSTRACT
Babesia are transmitted only by ticks; other vectors have never been identified with certainty. Since development may take place in each stage of a tick generation, eggs, larvae, nymphs, and adults, transmission and development of Babesia differ considerably from transmission of other protozoa by insects or annelids. Development of Babesia implies transmission of the intracellular parasites from one host cell to the next, from one stage of the tick host to the next, from the tick to the mammalian host, and vice versa. Transmission patterns have been observed: typical tick species acquire infection only in the female stage; transformation of Babesia erythrocytic stages into sexual stages and finally sporokinetes occur in the gut of the replete female tick, always followed by transovarial transmission. Obviously, adaptation of Babesia bigemina to Boophilus microplus has occurred in endemic areas to the extent that the ovary and the salivary glands of the female tick become infected simultaneously, thus securing transovarial infection.
