Background: Babesiosis is an emerging tick-borne disease caused by intraerythrocytic protozoa of the genus Babesia. More than 100 species infect a wide range of wild and domestic animals worldwide. Human infection is limited to a smaller group of species. The majority of reported human infections are caused by B. microti and B. duncani in the USA, and B. divergens and B. venatorum in Europe1. The first reported case in Australia of locally acquired babesiosis, caused by B. microti, was published in 20122. This study aimed to investigate the possible presence of Babesia spp. in Australians with chronic symptoms of tick-borne illness.
Method: Whole blood and serum samples were taken from 55 test participants with symptoms of tick-borne illness and 28 age and sex-matched healthy controls. Test participants were recruited from New South Wales, Queensland, Victoria and Western Australia. Giemsa-stained thin blood smears were prepared to directly detect intracellular Babesia parasites. Polymerase chain reaction (PCR) was employed to amplify three genes to detect Babesia DNA. Indirect immunofluorescence (IFA) was used to detect IgG antibodies against B. microti and B. duncani.
Results: Thin blood smears were negative for all participants. PCR results are inconclusive at this stage. 10 test participants and 1 control demonstrated IgG sero-reactivity to B. microti while 6 test participants and 1 control were IgG sero-reactive to B. duncani via IFA. 3 test participants were sero-reactive against both B. microti and B. duncani.
Conclusions: Sero-reactivity to Babesia antigen suggests past exposure or infection with Babesia. PCR results will be confirmed via vector cloning. One sero-reactive participant had not reported overseas travel suggesting local exposure to Babesia spp. Further investigation is required to determine possible sources of exposure to Babesia in Australia.