Ultrastructure of Babesia major in the tick Haemaphysalis punctata.

Haemaphysalis punctata ticks were infected with Babesia major by allowing them to feed on an infected splenectomised calf. Heavily infected ticks were dissected and the guts and the ovaries were processed to study the ultrastructure of B major in these organs. The morphology of the parasites in the gut and the ovary was identical. It was shown that the parasite contained a reduced form of an apical complex consisting of characteristic organelles such as the polar ring, rhoptries, micronemes and microtubules. A primitive conoid was situated at the anterior end of the parasite and consisted of delicate helical rings. The occurrence of these organelles confirmed the inclusion of this parasite in the subphylum Apicomplexa.