Type II and III parasites are more

Type II and III parasites are more efficient than type I parasites at establishing infection in vivoTo determine if parasite strain can affect parasite burden and host response in our zebrafish model, we infected larvae with ~5×103 type I, type II or type III Toxoplasma-GFP (Sup. Fig. 2A). In all cases, infected larvae show 100% survival and no adverse effects up to 48hpi (Sup. Fig. 2B). Analysis by fluorescent stereomicroscopy showed, from initial parasite input, parasite burden is reduced ~95% by 6hpi, suggesting ~5% of parasites successfully invade zebrafish cells and establish infection. To quantify parasite burden in a high-throughput manner we optimized an automated quantification pipeline using ZedMate (37) for the different strain types at 6 and 24hpi. Strikingly, type II and III parasite burden is ~3x higher than type I parasite burden at 6hpi (Fig. 2A and B, Sup. Fig. 2C). However, once established at 6hpi, all 3 strain types persist equally and decrease by ~20% between 6 and 24hpi.