Your vet tells you to prevent your pets from licking the family's face. She lists the numerous parasites and bacteria possibly present in pet saliva that can affect family members. However, recent research suggests that the ancient practice of licking dogs can aid wound healing.
So is pet saliva a health hazard or a benefit? The answer is probably both. However, routine veterinary care and simple sanitary practices can reduce fears that your pet's licking is a risk to family health.
Why are your pet's kisses dangerous to health?
The mouth and intestines of pets can harbor bacteria and parasites that can be transmitted to humans. They can cause a variety of medical conditions in humans. Diseases transmitted from animals to humans are called "zoonotic" (zo-not-ick).
Pastuerella is a normal inhabitant of the mouth in cats and dogs that can cause skin infections, lymph nodes, and sometimes more serious infections. Bartonella henselae, a bacterium that is transmitted to cats from infected fleas through their feces. It is the cause of a serious infection of the skin and lymph nodes called cat scratch fever. The Center for Disease Control reports that most pastuerella and bartonella infections are the result of scratches. Little data is available to substantiate that being licked by a pet is an important means of infection.
Salmonella, E. coli, Clostridia, and Campylobacter are intestinal bacteria from pets that can cause serious intestinal diseases in humans. Pets can be symptom free and pass these bacteria in their feces (poop). Most human infections are generally due to oral contact of hands contaminated by pet feces or feces. Because pets lick their anus, these bacteria can also be present in their mouths. Facial and lip licking is a potential route of infection from pet to human. Again, there is little evidence that this is actually an important transmission medium.
Pets are hosts for many parasitic worms and single-celled parasites. Human infection by these parasites can lead to intestinal diseases, skin problems, blindness, and brain disorders. Pets can live with these parasites in their intestines without signs of disease. But the eggs that pass in the feces of pets can infect humans. Like bacteria, the main route of infection in humans is fecal-oral. Pets that have licked their anus can pass parasite eggs to humans during facial licking.
With the exception of two single-celled parasites, Giardia and Cryptosporidia, this type of infection is not likely. Most parasite eggs are not infectious directly from the anus. They must undergo a maturation period in feces or contaminated environment to infect humans. Transmission to humans would require dogs to lick human faces after having bitten or eaten feces that were one to 21 days old, depending on the parasite. Because cats are not fecal eaters (coprophagic), humans are unlikely to be infected with parasites from their cats.
Giardia and Cryptosporidia are immediately infectious so they could potentially be transmitted through a lick.
The benefits of pet saliva
The belief in the healing power of a dog's licking dates back to ancient Egypt and persisted through time. In modern France, a medical saying translates to "The language of a dog is the language of a physician." Recent research has identified products in saliva that actually aid healing.
Researchers in the Netherlands identified a chemical in pet saliva called histatins. Histatins accelerate wound healing by promoting the spread and migration of new skin cells.
Dr Nigel Benjamin from the London School of Medicine has shown that when saliva comes into contact with the skin, it creates nitric oxide. Nitric oxide inhibits bacterial growth and protects wounds from infection.
Researchers at the University of Florida isolated a protein in saliva called nerve growth factor that cuts wound healing time in half.
Prudent precautions with pet saliva
The risk of bacterial or parasitic infection from pets is greatest for very young children, the elderly, and immunosuppressed individuals receiving chemotherapy or suffering from AIDS. People with healthy immune systems are unlikely to be infected. Despite the relatively low risk of infection from pets, some sensible precautions on the part of pet owners are in order. The Companion Animal Parasite Council recommends:
Regular deworming programs
Annual pet fecal exams with appropriate deworming treatment
Treatment to control fleas and ticks
Daily removal of pet feces and compliance with pooper-scooper laws
Covering children's litter boxes when not in use
Feeding cooked, canned, or dry pet food
Washing or cooking vegetables for human consumption
Proper hand washing after exposure to feces or fecal contamination.
By Ken Tudor, DVM