Honestly I don't get how they deem the risk of infection acceptable, especially with leeches of unknown origin. They could carry a myriad or blood-born diseases

Honestly I don't get how they deem the risk of infection acceptable, especially with leeches of unknown origin. They could carry a myriad or blood-born diseases. They are more than likely to have been used on ill humans before. Are they thoroughly tested for all cases? I honestly doubt it. Just incinerate them and breed clean ones. And it's not like their anti-coagulant abilities are irreplaceable. Sure, they come in a convenient package but that's all.