P. yoelii 17XL induces ultra structural changes in mouse cerebellum at peak parasitaemia (day eight post-infection) [scale bar: 1 μm]. Cerebellum from parasitized mice was ultra structurally analysed by transmission electron microscopy to evaluate effects of P. yoelii 17XL infection on brain micro vessels. Uninfected mice (Mag. × 15000) show normal intact micro vessel endothelia (ME) at blood brain barrier (BBB). Infected mice (six out of 10) [Mag. × 15000] show disintegrating ME and BBB (arrow) of brain vessels examined at day eight post-infection. Erythrocytic (RBC) adherence in the microvessels, but not leukocytic (WBC) adherence, was observed in the infected mouse brains examined.