It is rare for a dog or cat to make it through life without at least one parasite trying to make your pet it's home. A parasite is any organism that finds food or shelter on or in a dog or cat. A few examples are fleas, lice, ticks, worms, ear mites, maggots, etc. Parasites can live in your pets' ears, eyes nose, mouth, intestines, bloodstream, not to mention just about anywhere on their body.