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How man’s best friend can become his worst enemy

Showing affection towards a cute and friendly domestic pet has become more than just a habit or interest - it has become a necessity in some cases. However, as Laleh Lohrasbi explains, animals such as dogs can transmit diseases to their owners that are irreversible.

The modern world has affected human lifestyle and manners a lot. More work, fewer marriages, less human interaction and more loneliness have led people to substitute animals for normal human contacts with partners, children or family members. Many elderly people for instance, like having a dog instead of being alone at home. There are approximately 93 million pet dogs in the U.S., Canada and Western Europe. Most of these pets live with their owners inside the house, sleep with them in their beds, take care of their little babies, hug them, lick their faces and sometimes even eat with them, following the old myth that a dog’s mouth and body are much cleaner than a human’s. In France, a medical saying translates to “A Dog’s Tongue is a doctor’s tongue”. Unfortunately, it seems that  the licking and kissing of owners’ faces by their dogs has become acceptable.

There are hundreds of different types of bacteria, parasites and viruses of all sorts in a dog’s mouth. Just looking and monitoring what a dog does during the day makes it very easy to understand why. Dogs not only use their tongues to clean themselves but just shove their faces into anything smelly like dead birds, animal carcases, the litter box, other animal droppings or the posterior of another dog! The germs in their mouth can also easily spread to other parts of their body by scratching and itching of the body with the tongue which means other parts of the body will also be unclean. So kissing dogs on their snout or the top of their heads is not safer than kissing them on the mouth.

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Recent research has identified products in saliva that indeed aid in healing wounds. One of these compounds is called histatins, which speed wound healing by promoting the spread and migration of new skin cells. Dr Nigel Benjamin of the London School of Medicine has also shown that when saliva contacts 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 halves the time needed for wound healing. But Dr Nandi, an assistant professor of medicine at Drexel University College of Medicine in Philadelphia, believes that although dog saliva has proteins that may help cleanse or heal its own wounds, there are also some organisms unique to dogs that humans are simply not meant to tolerate or combat.

“Most animals’ mouths are host to an enormous oral microbiome of bacteria, viruses and yeast.” Dr Nandi told the New York Times. Some of these bacteria are zoonotic bacteria which mean that if they pass  from animals to humans they can cause diseases. Some of these zoonotic bacteria are Pasteurella, clostridium, E-coli, salmonella and campylobacter which can cause severe gastrointestinal disease in humans.

If dog saliva touches intact skin in a healthy person, it is unlikely to cause a serious problem, because there will be very little absorption through the healthy skin. However, a dog’s saliva and its germs can easily be absorbed through the mucous membranes of a person’s nose, mouth and eyes. That is why vets strongly advise against dog’s licking the faces of their owners.

According to the New York Times, Dr Nandi believes that hookworms and roundworms are other infections which can be transmitted from dogs to a human in a practice called coprophagia, in which animals ingest one another’s stool or lick each other’s anuses. It can even happen when dogs lick themselves. Studies show that a puppy could have as many as 20 million to 30 million roundworm eggs in its intestinal tract in one week. Dr Joe Kinnarney, of the American Veterinary Medical Association, said a client’s child at his practice in Greensboro, N.C., nearly lost an eye from a roundworm infection. However, pets may live with these parasites in their intestines with no signs of illness.

The experts believe that not all people can get sick from dog licking, but some people are more susceptible. For example kids and little babies whose immune systems are not fully developed are the most vulnerable groups. Those with compromised immune systems including diabetic patients, and patients receiving chemotherapy are another high-risk group. Pregnant women, elderly people and people with open sores on the face like teenagers with pimples are also at a greater risk.

It is interesting that in Islamic tradition the Prophet Muhammad(s) has been reported to have said that when a dog licks a utensil, rub it with earth (sand) and wash it three times. Keeping and raising guard dogs and sheepdogs for some people is a necessity. Islam allows and encourages kindness and compassion towards animals, but treating animals as part of the human family could be hazardous for humans.

 

Lohrasbi

 

 

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