Isolation and preliminary characterization of a large Babesia sp. from sheep and goats in the eastern part of Gansu Province, China.

Two species of Babesia were isolated from naturally infected sheep in the eastern part of Gansu province. One of the species was identified as B. ovis, while the another one seems as yet to be an unidentified Babesia species. The latter could be transmitted transovarially by Haemaphysalis longicornis. It was shown that larvae and nymphs transmit the organism to sheep and goats with a prepatent period of 5-28 days. As the carrier period of B. ovis is longer than that of the larger species and the prepatent period of the larger Babesia is shorter than that of B. ovis, it was possible to isolate the unidentified larger species. The larger Babesia is polymorphic, including double pyriform, single pyriform, ring-form, rod-like, three-leafed and budding forms. The size of typical paired pyriforms was 1.8-2.5 microm x 0.9-1.8 microm, with mean dimensions of 2.21 +/- 0.12 microm x 1.17 +/- 0.18 microm. The parasite causes a severe course of infection associated with a parasitaemia as high as 23.7% and with a high mortality rate in both sheep and goats, being very marked in lambs and imported small ruminants.