Comparison of the degree of red blood cell contamination using two different purification methods. Enriched ookinete preparations were resuspended in an equal volume of oocyst medium and the degree of contamination by red blood cells and debris was assessed using an equal volume of parasite material. Preparations were viewed at a magnification of × 400. Ookinetes are indicated by an arrow. Scale bar = 10 μm. Note heavy contamination with other parasite stages/cellular debris following purification on a Nycodenz cushion.