Can a porch potty become infected with worms I found a worm on the porch potty but according to my vet the dog doesnt have worms and I've never seen them in his poo?

It is caused by flies when they land on dog pooh. They lay their eggs, which can be 40-50 at a time. the larvae first appears as tiny looking brown seeds. when they hatch into what is called pupae theybtorn into tiny maggots.. it only takes one fly. I have stopped it by cleaning up the pooh immediately after my dig goes, and I have an 80 lb. mix. when he occasionally has a loose stool, I have a mix of Mr Clean, the new one that has fabreeze in it, in a spray bottle mixed with water and immediately clean it. stops odor and doesn't stop my dog from using it.