Bottle flies are not just an annoyance. It is important to remember that bottle flies feed on garbage, sewage and animal carcasses. As a result, bottle flies may carry pathogenic bacteria that can infect the food in your home. In addition, fly larvae can infest human tissues. An infestation can sometimes even be created on unbroken skin. These infestations, called myiasis, can lead to severe irritation and pain. In extreme cases myiasis infections can be fatal.