Observation of a novel Babesia spp. in Eastern Grey Kangaroos (Macropus giganteus) in Australia.

ABSTRACT

The roles and epidemiological features of tick-borne protozoans are not well elicited in wildlife. Babesia spp. are documented in many domestic animals, including cattle, horses, pigs, dogs and cats. Three cases affecting eastern grey kangaroos are described. The kangaroos exhibited neurological signs, depression and marked anaemia, and microscopic examination of blood smears revealed intraerythrocytic piroplasms. One to seven intraerythrocytic spherical, oval, pyriform and irregularly-shaped parasites consistent with Babesia spp. were seen in the blood smears and the percentage of infected erythrocytes was estimated to be approximately 7% in each case. Data suggest that the tick vector for this kangaroo Babesia sp. is a Haemaphysalis species. For Case 2, ultrastructural examination of the erythrocytes of the renal capillaries showed parasites resembling Babesia spp. and 18 of 33 erythrocytes were infected. DNA sequencing of the amplified 18S rDNA confirmed that the observed intraerythrocytic piroplasms belong to the genus Babesia. The phylogenetic position of this new kangaroo Babesia sp. (de novo Babesia macropus), as a sister species to the new Australian woylie Babesia sp., suggests a close affinity to the described Afro-Eurasian species Babesia orientalis and Babesia occultans suggesting perhaps a common ancestor for the Babesia in kangaroos.