Department of Parasitology, Liverpool School of Tropical Medicine, Pembroke Place, Liverpool, L3 5QA2, UK. john.archer.jpa@gmail.com.|Department of Parasitology, Liverpool School of Tropical Medicine, Pembroke Place, Liverpool, L3 5QA2, UK. gareth.whiteley@lstmed.ac.uk.|Department of Parasitology, Liverpool School of Tropical Medicine, Pembroke Place, Liverpool, L3 5QA2, UK. nicholas.casewell@lstmed.ac.uk.|Department of Parasitology, Liverpool School of Tropical Medicine, Pembroke Place, Liverpool, L3 5QA2, UK. robert.harrison@lstmed.ac.uk.|Department of Parasitology, Liverpool School of Tropical Medicine, Pembroke Place, Liverpool, L3 5QA2, UK. simon.wagstaff@lstmed.ac.uk.