Like T. gondii, Cryptosporidium parvum and Cryptosporidium hominis usually cause a self-limiting disease in healthy individuals but represent a manifest problem in immuno-compromised patients, particularly those with AIDS, where infection leads to acute and protracted life-threatening gastroenteritis (Chen et al. 2002). More recent data have led to a radical reassessment of the impact of cryptosporidiosis, with the number of Cryptosporidium-attributable diarrhoea episodes estimated at >7·5 million in children aged <24 months in sub-Saharan Africa and South Asia where infection is estimated to contribute to >250 000 infant deaths per year (Sow et al. 2016). Current treatment of cryptosporidiosis relies on a single FDA-approved drug, nitazoxanide, which has limited efficacy in those most at risk. More recently, the repurposing of antimalarials, e.g. quinolones and allopurinols, has been proposed (Gamo et al. 2010; Chellan et al. 2017).