He bred his mosquitos in a bio-containment lab and he also used a species that's not native to the US so that even if some did escape, they'd just die off, there'd be nothing for them to mate with.
Allevò-le zanzare in un laboratorio  di bio contenimento e usò anche specie non autoctone, cosicchè se qualcuna scappasse morirebbe, poiché  non si potrebbe accoppiare.