Flies pick up bacteria from decaying matter and transfer it to food. Flies defecate every four to five minutes on average and are known to carry more than 100 pathogens. They can transmit serious diseases like typhoid, tuberculosis, cholera, dysentery, hepatitis, salmonella and parasitic worms. They can also be problematic for livestock or pets, sometimes laying eggs in the crotches of livestock. Larvae can infest on livestock, while adults are both a nuisance and spread germs.