Dogs, cats and rabbits all get parasites, in fact most puppies and kittens have worms which they pick up from their mothers, as pregnancy usually reactivates dormant worms in the mother.
Parasites, such as worms living inside the animal, or fleas, ticks or mites living on the skin, will often cause some signs of disease. However, it is also possible for pets to be infected with parasites without any obvious signs that they are carrying them. Some of these parasites can affect humans, and it is therefore important to treat your pet regularly for parasites, even if you do not think that there is a problem. This is particularly true of treatment for roundworms, as they can occasionally cause serious sight-threatening disease in people.