November 21st, 2018
Human babesiosis is an emerging tick-borne disease caused by apicomplexan parasites of the genus Babesia. Clinical cases caused by Babesia duncani have been associated with high parasite burden, severe pathology and death. In both mice and hamsters, the parasite causes uncontrolled fulminant infections, which ultimately lead to death. Resolving these infections requires knowledge of B. duncani biology, virulence, and susceptibility to antiinfectives, but little is known and further research is hindered by a lack of relevant model systems. Here, we report the first continuous in vitro culture of B. duncani in human red blood cells. We show that during its asexual cycle within human erythrocytes, B. duncani develops and divides to form four daughter parasites with parasitemia doubling every ~22 h. Using this in vitro culture assay, we found that B. duncani has low susceptibility to the
four drugs recommended for treatment of man babesiosis, atovaquone, azithromycin, clindamycin and quinine, with IC50 values ranging between 500 nM and 20 μM. These data suggest that current practices are of limited
effect in treating the disease. We anticipate this new disease model will set the stage for a better understanding of the biology of this parasite and will help guide better therapeutic strategies to treat B. duncani-associated babesiosis.