just as a precaution, i try to avoid wild filth flies because they do visit some truly nasty stuff. its still going to happen occasionally anyway. i am sure he will be fine, even if some undesirable was transmitted , it wouldnt likely make him sick anyway. many chams go years with parasitic infections and no obvious physical signs of infection,(thats why we do fecal microscopy) that being said, i believe, it is still good husbandry to try to reduce the risk of infection by offering only wholesome feeders, many wild feeders would be on that list, but i do not consider wild flies one of them. thats why its still a good practice to do yearly fecals regardless of what they have ingested. thats not to say you need to run out and do a fecal because you saw him eat a wild fly, even if there was some sort of transmission, it could easily be months or longer before it would show up on a fecal. so i would say do your best to offer only wholesome feeders, but no need to worry about the occasional wild fly, as long as you do yearly fecals, just a good practice anyway. jmo