I The occurence of the parasites in Australia
The three piroplasms studied occur naturally in Australia (Seddon, 1952). They are blood parasites of the bovine and are known locally as Babesia bigemina (Smith and Kilborne), Babesia argentina (Lignieres) and Theileria mutans (Theiler). These organisms are show in Plates 1-3.
Piroplasms are non-pigmented, protozoan parasites of variable pathogenicityj both Babesia and Theileria are foxmd in the red blood cells of the vertebrate host, whereas the latter genus undergoes development in lymphoid tissue as well (Wenyon, 1926).
Both B.bigemina and B.argentina are transmitted by the tick, Boophilus microplus (Canestrini). Because of an early observation (Dodd, 1910), it has been believed that T.mutans is also transmitted by this vector, but this was not confirmed during the present work. According to Seddon (1952), species of Haemaphysalis are probable tick vectors of T.mutans in Australia.
Species of Eperythrozoon Schilling and Borrelia Swellengrebel are other blood parasites of Australian cattle (Seddon, 1952;1953). Whereas it appears that two species of the former organism are found here (Hoyte, personal commimication and see p. 85 ), the situation regarding the latter is not clear. Mulhearn (1946) considered that the spirochaete (which has in the past been known as Spirillum, Treponema and Spirochaeta) was transmitted by B.microplus and was identical with Borrelia theileri; Wenyon (1926) stated that B.theileri was 20-30µ in length; during the present work, however, a species of Borrelia measuring 8-18µ was found. Thus, it is now not known whether one or more species of Borrelia are present in Australia. Eperythrozoon sp. and Borrelia sp. are shown in Plates 4 and 5, respectively. ...............................................