Toxoplasma gondii is a tiny organism, slightly bigger than a bacterium, called a protozoa. This parasite has a worldwide distribution, except in the absence of cats. Cats are the only animals capable of completing the life cycle of this organism. Other warm blooded animals, including cats can serve as intermediate hosts for the parasite. The organism has a very high prevalence, but rarely causes clinical disease in dogs and cats. This is an important parasite to be aware of due to the fact that it is an important zoonosis, meaning it is an animal disease that can be transmitted to humans.