> We already have medicines that treat the problem

We do have treatments of screwworm infestations, but it involves physically removing the larva and usually removing tissue as well as systemic treatments like antiparasitics. It's labor intensive and not cheap.

It also doesn't actually fix the _overall_ problem because screwworms will happily lay eggs in wild mammals too and so you will constantly be treating your livestock.

> We've had it solved for a long time

Yes, we solved it with mass releases of sterile flies over decades.