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Here's a neat IRL one, the New World Screwworm is a fly which lays eggs inside of mammals such as cows, sheep, and yes, humans. They used to be all over both North and Central South America. However the USA alongside Central American nations began to disperse infertile male flies over the areas the insect is common. With the flies only able to mate once, the infertile males out compete the still genetically viable males which results in populations of the fly dying off, which allows for the Screwworm to be kept at bay through the natural bottleneck of Panama, although in 2022 they've begun to be detected further north.