Cooking oils will not be effective because they will be digested. The feeding of Vaseline, however, should be separated from meals in order to minimize the loss of fat soluble vitamins. Most animals, if gently initiated, will consider this ritual a treat. Worms can usually be detected by a simple stool sample analysis. To check for tapeworms, however, you must see the worm segments in the stool of your animal.
Dogs acquire tapeworms primarily by eating fleas.
Cats acquire tapeworms also by eating other animals. Whip worms are often difficult to find in the stool, making repeated analyses necessary. Heart worms are detected by a blood test. Parasite eradication is necessary for the general well-being of your animal. In the context of this hand-out, it is necessary because parasites activate the immune system, making it more responsive to other stimuli which might cause itch.