The ancient Greeks, for example, were aware that rabies could be transmitted through dog bites. The list of known animal-transmitted diseases constantly changes, as improved diagnostic techniques identify zoonoses previously mistaken for more common exclusively human diseases. For example, in the 1960s, the role of felines in transmitting toxoplasmosis in their feces was discovered. In addition, travel to more remote parts of the world by people and the increased international commerce in exotic animals have added to the list of zoonoses. Fortunately, most zoonoses are rare, and almost all can be treated once a diagnosis is made.
Scientists estimate that virtually all puppies have roundworm.
Symptoms of roundworm in humans are fever, headache, cough, and poor appetite. However, it is more resistant to elimination with anthelmintic drug treatment than the egg-producing contagious type of infection found in the puppies. Egg-producing infections may be found in adult dogs, although less frequently than in puppies. This can be risky, though, because immature animals, including dogs, are very sensitive to any drug therapy. Such treatment should only be undertaken if it is recommended by a veterinarian.