(A) CRISPR-Cas9 editing of the parasitic flatworm Opisthorchis viverrini (left) involved using a technique called electroporation. This forced cells to accept a bacterial plasmid construct (black circle) that encodes a Cas9 enzyme (red) and a guide RNA (green) that targets the Ov-grn-1 gene in the flatworm. The gene codes for a protein that may help trigger liver cancer in infected individuals. (B) The adult female Schistosoma mansoni (thinner dark gray worm of the pair) produces eggs while embraced by the male worm (broader light gray worm of the pair). Two methods were used to introduce CRISPR-related materials into these eggs. Electroporation helps the pre-complexed Cas9 protein (red) and strand of guide RNA (green) to get inside the eggs. Alternatively, a lentiviral virion (a particle derived from a virus; circle with black spots) can encapsulate and deliver these elements into cells. The virion also carries several plasmids – pLV-ω1 × 1 (green and red), pHIV spg (magenta), VSVG (blue) – which help the virus package and insert Cas9 and the single guide RNA inside cells. Both approaches target the Sm-omega-1 gene, which codes for a protein that may be involved in damaging the organs of people who carry the worm.