Some of them hide their eggs in little pockets all over the body. The eggs won't hatch until the mother dies off. She puts off a hormone to keep them dormant, so she won't have to compete with them for food. Other parasites have tiny little eggs that float in the air. If you leave a glass of water uncovered over night, eggs drifting in the air like dust will settle in the water. The next morning you drink parasite eggs along with the water. They are ubiquitous. That is why routine maintenance is necessary. Once a host, always a host, unless we can figure out how to get our immune systems to kick in and prevent them from coming back. I have heard that blood cleansing can do that. So I am taking herbs to cleanse my blood regularly. And make smoothies with raw beets.