[1] Northwick Pk Hosp & Clin Res Ctr, Dept Infect Dis & Trop Med, London, England
[2] Univ Glasgow, Inst Biodivers Anim Hlth & Comparat Med, Glasgow, Lanark, Scotland
[3] Univ Glasgow, Wellcome Ctr Mol Parasitol, Glasgow, Lanark, Scotland
[4] Imperial Coll London, Fac Med, London, England