MEXICO CITY — Illegal cattle ranching in Central America has led to the spread of a deadly parasite long thought to be eradicated, and conservationists are calling for tighter controls before it reaches Mexico and the US. An outbreak of new world screwworm (Cochliomyia hominivorax)  — a fly that infects warm-blooded animals — is the … Continue reading A deadly fly is spreading through Central America. Experts blame illegal cattle ranching