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Fig. 1 | Parasites & Vectors

Fig. 1

From: Extreme-QTL mapping of monepantel resistance in Haemonchus contortus

Fig. 1

Genetic cross between Haemonchus contortus isolates with extreme phenotypes for monepantel resistance. Sheep hosts were infected with 10,000 infective larvae (L3) of H. contortus from monepantel-susceptible (Par-S L3, in green) or monepantel-resistant (Par-R L3, in red) isolates. Hosts were euthanized after 14 days of infection and immature-stage larvae collected from the abomasum were sexed. Approximately 50 male and female H. contortus immature-stage larvae of the susceptible isolate (Par-S immature) were surgically inoculated into the abomasum of another sheep host as the parent to be crossed, respectively, with ~ 50 females and males of the resistant isolate (Par-R immature), resulting in two F1 progenies (F1-SR and F1-RS) after 36 days. The F1 generation was recovered as eggs on feces and cultured to L3, and approximately 5000 L3 were used to orally infect new sheep hosts for F1 intercrossing. Then, the obtained descendants (F2 generation; after 29–36 days) were used (n = 5000) to orally infect new sheep hosts. Sheep hosting the H. contortus F2 generation were treated with 2.5 mg/kg monepantel. Before treatment, eggs recovered on feces (after 28 days) were cultured to L3 to obtain the unselected group (US-SR and US-RS), consisting of a mix of susceptible and resistant worms of the F3 generation progenies. The same process was performed after monepantel treatment, resulting in the selected group (S-SR and S-RS), consisting of only surviving resistant worms, recovered after 39–40 days. Pools of 30,000 H. contortus L3 from the parental resistant isolate (Par-R) and from unselected and selected F3 generation progenies (US-SR, US-RS, S-SR and S-RS) were subjected to DNA extraction and genomic sequencing (Pool-Seq). White sheep: Ile de France breed; black sheep: Santa Ines breed

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