Diseases We Can Acquire From Dogs
( Originally Published 1936 )
Hydrophobia is the most serious disease which can be transmitted from the dog to man. It is, in fact, the most serious disease that an animal can transmit to man.
Of course, it can only be transmitted in one way—that is, by a rabid or mad dog's biting a human being or dripping saliva on an open wound or break in the skin.
As is pointed out in more detail on page 104, there is a special danger in trying to help a pet dog which appears to have a bone stuck in the throat. The symptoms of rabies include a paralysis of the muscles of the jaw, and what appears to be a bone stuck in the throat is actually this paralysis. When somebody tries to put his finger down the dog's throat to dislodge the bone, the infective saliva frequently gets into an opening in the skin and produces hydrophobia.
Man is not nearly so liable to the disease as the dog, and apparently only about 15 per cent of human beings who are exposed take the disease.
Another disease which is transmitted from the dog is called "echinococcus." It is rare in this country, but frequent in countries where sheep herding is carried on. It is endemic in Norway and in Greece. Most of the patients with the disease seen in the United States are immigrants from one of these countries.
Echinococcus disease comes from the tapeworm of the dog. The dog gets it from the sheep. Like all parasitic diseases, the cycles in different animals are extremely interesting. In the sheep, a larval form of the worm is found, and this gets into pools of water and enters the dog's intestine when he quenches his thirst at such a pool. In the dog the larvae develop into adult tapeworms; their eggs are cast out and the sheep eat them, and in the sheep's body the eggs develop only into the larval forms. The worm requires two hosts. In the sheep it develops only into young forms. In the dog alone does the adult form develop.
If the egg should get into a man's body a curious intermediate form is found, which burrows its way through the wall of the intestine and gets to various internal organs, usually the liver. Here it spins itself a sort of shell, and eventually a large cyst is formed. These cysts can be removed by surgery.