Humans living in areas where the population of parasitic flies is particularly dense are at risk of contracting myiasis. Flies reproduce by laying their eggs in animal tissue, but not every animal is an equally suitable host. For most animals, larval infestation is relatively rare, but domestic sheep are unusually prone to infection by parasitic flies. And sheep are especially common in proximity to human populations, in areas where they are kept as livestock.
The information in the passage most strongly supports which of the following?