Coming from a family that has cattle and dairy cows in south eastern Brazil, where screwworm is endemic, I was surprised when I listened to a podcast about screwworm, and some of the descriptions about how huge the problem was in the US. After some research it appears it affects more climates that are always hot and humid, and big operations where the animals are not being checked frequently. Also the handling at the 60s was probably much worse than modern techniques for avoiding animals being hurt and treating when they are infected.
