Diseases that pet dogs can transmit

By EDUARDO GONZALES, MD

December 20, 2010, 4:37pm

Q: My six-year-old son is very fond of dogs that is why I am thinking of gifting him with one, but I am wary of possible diseases that a dog can transmit to him. Are there diseases that dogs can transmit to humans?
--Liza B., Manila

A: Animals, like humans, are susceptible to a multitude of infectious and parasitic illnesses. Fortunately, most infections are species specific, which means the majority of microorganisms that cause disease in lower animals do not affect people. Thus, illnesses that are common and highly fatal among pet dogs such as distemper, canine parvovirus, and heartworms cannot be transmitted by dogs to humans.

However, and this should answer your question, there are infectious diseases, called zoonoses, that animals can transmit to humans. In fact, there are more than 200 of these zoonoses that are caused by bacteria, viruses, parasites, and fungi that animals harbor, but only a few can be passed on by dogs.

The most dreadful disease that pet dogs can transmit to humans is, without doubt, rabies. Rabies is caused by a virus that resides in the saliva of infected animals and is transmitted to a human through a bite, or rarely, when the animal’s saliva gets in contact with a scratch or fresh break in the skin. Incidentally, humans cannot get infected with the rabies virus by eating the meat of a rabid animal, provided the meat is cooked. Signs of rabies include personality and behavioral changes, incoordination, hydrophobia, muscle spasms, and seizures. There is no cure for rabies and it is always fatal.

Another common infection that can be passed on by dogs is campylobacter infection, which causes diarrhea, abdominal pain, and fever in people. This illness is brought about by campylobacter jejuni, a bacterium that inhabits the intestinal tract of dogs, cats, hamsters, birds, and some other domestic animals. The bacteria can infect a person by direct contact or by intake of contaminated water or undercooked meat (of fowls).

Skin disorders that can be acquired from pet dogs include ringworm and scabies (galis aso, in Filipino). Ringworm is caused by several types of fungi that humans can get by touching infected pets. Typically, the lesions of ringworm consist of itchy ring-shaped skin patches.  Scabies, on the other hand, is caused by mites that burrow under the skin. It is characterized by an itchy pinpoint red rash, scaly skin, and hair loss.

Ectoparasites that infest pets such as fleas and ticks can turn on, and bite, humans and give rise to itchy lesions that are prone to secondary bacterial infection. Ectoparasites are also vectors for a number of infectious diseases, which happily rarely occur nowadays.

Parasites that plague dogs such as the round worm Toxocara canis can also affect humans. Toxocara worms reside in the intestines of infected dogs. When their eggs pass in the stools, they contaminate the soil. If ingested by humans, the eggs hatch in the intestines and the larvae migrate all over the body. Often, toxocara infestation is mild and causes no symptoms but sometimes it can give rise to fever, cough, skin rashes, and swollen lymph nodes (kulani, in Filipino). Migrating larvae can also damage various organs especially the liver and the eyes.

Thus, a pet dog can really transmit infections to your kid, but this should not prevent you from buying him one and making him miss out on the companionship and affection that a pet can offer. In the first place, the chance that a dog can make your son sick is small.  You can even reduce this risk further by practicing these measures: keep you and your dog’s house clean and free of fleas and other ectoparasites; have your dog completely and regularly immunized and dewormed; and, teach your son good personal hygiene.

When in Cebu City, please visit gregmelep.com for your real estate and retirement needs.

 (Email inquiries on health matters to: medical_notes@yahoo.com)