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.To test if host mitochondrial association is observed across the three strain types, we stained host mitochondria in the HBV of infected zebrafish larvae. In agreement with in vitro observations (36), both type I and type III parasites (and not type II parasites) show clear host mitochondrial association (Fig. 2C). These results demonstrate that strain type-dependent host mitochondrial association characteristics are conserved in zebrafish in vivo.