These data were generated related to the study of the Genetic architecture of transmission stage production and virulence in schistosome parasites. Abstract: Both theory and experimental data from multiple pathogens suggest that the production of transmission stages should be strongly associated with virulence, but the genetic bases of parasite transmission/virulence traits are poorly understood. In the blood fluke Schistosoma mansoni, parasite genotypes show extensive variation in numbers of cercariae larvae shed from infected snails. Furthermore, high shedding parasites cause high mortality to snails while low shedding parasites cause low mortality, consistent with expected trade-offs between parasite transmission and virulence. To understand the genetic basis of transmission stage production/virulence, we conducted reciprocal crosses between schistosomes from two laboratory populations that differ 8-fold in cercarial shedding and in their virulence to inbred snail hosts. Each parasite generation, we determined four-week cercarial shedding profiles in inbred Biomphalaria glabrata snails infected with single parasite larvae. We sequenced the whole genome of the F0 parents and the exome of the F1 progeny and 188 F2 progeny from each cross, and used linkage mapping to reveal quantitative trait loci (QTLs) underlying transmission stage production. Cercarial production is polygenic: we found three major QTLs on chromosome 1, 3 and 5 (Log-of-the-odds (LOD) = 5.61, 8.19, 6.25) and two minor QTLs on chromosome 2 and 4. These QTLs act additively and explained 28.56% of the phenotypic variation in cercarial shedding. Alleles inherited from the high and low shedding parents were co-dominant at all QTLs, except for chr. 1 and chr. 4 where the “high cercarial shedding” allele is recessive. These results demonstrate that the genetic architecture of key traits directly relevant to schistosome ecology can be dissected using classical linkage mapping approaches, and set the stage for fine mapping and functional validation of the genes involved using the growing armory of functional and cell biology tools available for this parasite. This dataset is made of 4 tables: F0_parental_populations.csv F1.csv F2.csv sex.tsv F0_parental_populations.csv This table contains the number of cercariae produced by each individual Biomphalaria glabrata Bg26 snails infected with single genotypes of Schistosoma mansoni parasite. We have compared the transmission stage production between two different populations of S. mansoni parasite. This dataset was originally published in Le Clec'h et al., 2019 (Striking differences in virulence, transmission and sporocyst growth dynamics between two schistosome populations. Parasites and Vectors. 2019 Oct 16;12(1):485. doi: 10.1186/s13071-019-3741-z). This table is made of 9 columns: id: the unique identifier of each sample. schistosoma_population: the population of schistosome used for the infection of the snail. Each snail was infected with a single parasite genotype. We have used SmLE (high shedder/highly virulent population) and SmBRE (low shedding/low virulent population). Shed.1: the number of cercariae produced by each parasite genotype at the first shedding week (4 weeks after exposure to parasite). Shed.2: the number of cercariae produced by each parasite genotype at the second shedding week (5 weeks after exposure to parasite). Shed.3: the number of cercariae produced by each parasite genotype at the third shedding week (6 weeks after exposure to parasite). Shed.4: the number of cercariae produced by each parasite genotype at the fourth shedding week (7 weeks after exposure to parasite). sum: the sum of the cercariae produced by each parasite genotype over the 4 weeks of shedding (Shed.1 + Shed.2 + Shed.3 + Shed.4). average: the average number of cercariae produced by each parasite genotype over the 4 weeks of shedding. sex: the sex of each parasite genotype determined by PCR 1. F1.csv This table contains the number of cercariae produced by each individual Biomphalaria glabrata Bg26 snails infected with single genotypes of F1 progeny from the cross SmLE x SmBRE (see the manuscript for details). This table is made of 11 columns: id: the unique identifier of each sample. cross: F1A or F1B cross. Each snail was infected with a single parasite genotype from either F1A or F1B progeny. Shed.1: the number of cercariae produced by each parasite genotype at the first shedding week (4 weeks after exposure to parasite). Shed.2: the number of cercariae produced by each parasite genotype at the second shedding week (5 weeks after exposure to parasite). Shed.3: the number of cercariae produced by each parasite genotype at the third shedding week (6 weeks after exposure to parasite). Shed.4: the number of cercariae produced by each parasite genotype at the fourth shedding week (7 weeks after exposure to parasite). sum: the sum of the cercariae produced by each parasite genotype over the 4 weeks of shedding (Shed.1 + Shed.2 + Shed.3 + Shed.4). average: the average number of cercariae produced by each parasite genotype over the 4 weeks of shedding. PO: the total phenoloxidase activity in infected snail hemolymph, measured at 7.5 weeks post-exposure 2. Hb: the hemoglobin rate in infected snail hemolymph, measured at 7.5 weeks post-exposure 3. sex: the sex of each parasite genotype determined by PCR 1. F2.csv This table contains the number of cercariae produced by each individual Biomphalaria glabrata Bg26 snails infected with single genotypes of F2 progeny from the cross SmLE x SmBRE (see the manuscript for details). This table is made of 10 columns: id: the unique identifier of each sample. cross: F2A or F2B cross. Each snail was infected with a single parasite genotype from either F2A or F2B progeny. Shed.1: the number of cercariae produced by each parasite genotype at the first shedding week (4 weeks after exposure to parasite). Shed.2: the number of cercariae produced by each parasite genotype at the second shedding week (5 weeks after exposure to parasite). Shed.3: the number of cercariae produced by each parasite genotype at the third shedding week (6 weeks after exposure to parasite). Shed.4: the number of cercariae produced by each parasite genotype at the fourth shedding week (7 weeks after exposure to parasite). sum: the sum of the cercariae produced by each parasite genotype over the 4 weeks of shedding (Shed.1 + Shed.2 + Shed.3 + Shed.4) average: the average number of cercariae produced by each parasite genotype over the 4 weeks of shedding. PO: the total phenoloxidase activity in infected snail hemolymph, measured at 7.5 weeks post-exposure 2. Hb: the hemoglobin rate in infected snail hemolymph, measured at 7.5 weeks post-exposure 3. sex.csv This table contains the in silico sexing of F0 parents, F1 parents and F2 progeny of S. mansoni parasites. This table is made of 4 columns: id: the unique identifier of each sample read_depth: the read depth ratio between the Z-linked and pseudo-autosomal regions. ratio: computed ratio between the Z-linked and pseudo-autosomal regions. sex: the sex of each parasite genotype determined in silico: a ratio around 1 corresponds to a male carrying two Z chromosomes while a ratio around 0.5 corresponds to a female carrying only one Z chromosome. Notes: 1. Le Clec’h W, Chevalier F et al. Real-time PCR for sexing Schistosoma mansoni cercariae. Mol Biochem Parasitol. Jan-Feb 2016; 205(1-2):35-8.doi: 10.1016/j.molbiopara.2016.03.010. Epub 2016 Mar 26. 2. Le Clec’h W et al. Characterization of hemolymph phenoloxidase activity in two Biomphalaria snail species and impact of Schistosoma mansoni infection. Parasit Vectors. 2016 Jan 22; 9:32.doi: 10.1186/s13071-016-1319-6. 3. Le Clec'h et al. Striking differences in virulence, transmission and sporocyst growth dynamics between two schistosome populations. Parasit Vectors. 2019 Oct 16; 12(1):485. doi: 10.1186/s13071-019-3741-z.

Le Clec'h Winka was supported by Cowles fellowship from Texas Biomedical Research Institute (13-1328.021).