The dog and the flea
There was a dog named chester and a fleas named charlie. One day chester was walking in the park with his owner, Sally. While he was walking there was a flea who liked him so she was following him and then jumped on him into his fur. The flea was bitting chester making him very itchy. The flea is playing the roll of the host and the dog is playing the roll of the prey. Charlie, the flea is advantaging because she is getting the blood from the dog and the dog has disadvantages because as the flea is taking blood its hurting him.