Abstract
The first Australian case of human babesiosis was recently reported (Senanayake et al., 2012), and the infection is believed to have been locally acquired. Intra-erythrocytic parasites were identified at the Camberra Hospital, by microscopic blood film-examinations, in a 56YO man from NSW. Piroplasms (Apicomplexa) are protozoa comprising the (mainly) tick-transmitted genus Babesia. Human babesiosis, is caused predominantly by B. microti (USA) and B. divergens (Europe), and has recently been found in Asia, Africa and South America, but never before in Australia.
Objective. To investigate the genes for β-tubulin and 18S ribosomal RNA (18S rDNA), and confirm the phenotypic diagnosis of babesiosis in this patient. To reconstruct strain phylogeny and tentatively infer its origin, using multiple phylogenetic markers.
Method. An 18S rDNA consensus sequence of the parasite was obtained from the patient’s blood using several available PCR primers. A BLAST-search identified, in GenBank, sequences of B. microti resembling the query. An alignment of available B. microti sequences, was used to design five novel PCR primers sets, specific for the β-tubulin gene.
Results. All the novel β-tubulin primers provided strong amplification, which allowed successful sequencing and confirmation of the blood sample’s positivity for B. microti. A phylogenetic tree revealed clustering with North American B. microti isolates derived from a tick, humans and voles.
Conclusions. The five novel β-tubulin primer sets proved useful for confirming the 18S rDNA-based identification using a second locus. This is the first step towards unravelling the intriguing questions about the origin and epidemiology of this organism in Australia.