Map of life expectancy at birth from Global Education Project.

Wednesday, March 07, 2007

Man Bites Dog

Since this is a popular topic here, and also, as it turns out, in the medical profession, I thought I should do a bit more with the question of dog bites. Just after I first posted on the subject, BMJ happened to come out with a substantial discussion of the issue. Physicians see dog bites so often, whether in primary practice or the ED, that proper treatment is one of their most important skills. In a clinical review (subscription only) Marina Morgan and John Palmer write:

Bites and maulings by dogs, sometimes fatal, are a worldwide problem and particularly affect children. Every year 250 000 people who have been bitten by dogs attend minor injuries and emergency units in the United Kingdom, and some of them are admitted to hospital for surgical debridement or intravenous antibiotics. . . The “hole and tear” effect—whereby canine teeth anchor the person while other teeth bite, shear, and tear the tissues—results in stretch lacerations, easily piercing immature cranial bones. The biting force of canine jaws varies with the breed, from 310 kPa* to nearly 31,790 kPa in specially trained attack dogs. Large wounds, significant devitalisation, and high mortality can result, with the highest mortality in neonates (six times that in toddlers), who are usually bitten by household pets.

Eeew. Trevor Jackson, writing in the same journal in 2005 (and yes, even you common rabble can read this because it's more than six months old) asks, "Is it time to ban dogs as household pets?":

After tobacco, alcohol, and sports utility vehicles, how long will it be before public health experts get serious about the menace of widespread dog ownership? Despite ongoing research into dog bites and zoonoses, the occasional media outcry about pit bull terrier and rottweiler maulings, and legislation such as the United Kingdom's Dangerous Dogs Act of 1991, pet dogs and their owners have mostly been given a rather long leash. And yet it increasingly seems extraordinary to me—considering all the things that the law prevents us from doing—that it is legal for people to keep a potentially dangerous wild animal in their home. Or even, as many postmen and postwomen have discovered to their cost, in their front gardens. . . .
The usual rejoinder to complaints about dog behaviour is that it is the owners, and not their pets, that are to blame—which is precisely why dog ownership should be curbed. We need responsible dog owners, people say. Call me dogmatic, but responsible dog ownership is mostly a contradiction in terms . . .

By now, I can envision readers barking in outrage and wacking their computer monitors with a rolled up newspaper. There is absolutely no way that such a measure would even be proposed by any politician who wanted to avoid impeachment, followed by tarring and feathering and being run out of town on a rail. But that happens to be what I find interesting about this question. Why are we so devoted to Canis lupus familiaris? What is this relationship all about?

In the same issue, June McNicholas and colleagues discuss the broad evidence on pet ownership and human health. Despite some early studies showing benefits, the evidence generally does not support a conclusion that owning pets is associated with measurable reduction in disease. However, these authors invoke a broader definition of health, in which the emotional bonds people have with pets are valuable in and of themselves.

So what is this cross-species relationship all about? I'm not an expert on the subject, but it seems pretty obvious that the symbiosis between humans and wolves -- which is what dogs actually are -- arose in the context of hunting. It is easy to imagine packs of human and canine hunters discovering that they could benefit from cooperation. When humans domesticated food animals, it was a short step from hunting to herding. Today, a small minority of dogs still work as herders, and as hunting partners. Dogs also use their talents in law enforcement to sniff out drugs, bombs, fugitives and bodies, and in private security to guard junkyards and other places where valuables are stored. The United States military, uniquely among nations, uses dogs to torture prisoners. And of course, blind people use dogs for guidance.

However, the vast majority of dogs are simply family members, pampered and generally useless. As McNicholas et al put it, "Companionship—a commonly stated reason for pet ownership—is regarded as theoretically distinct from social support in that it does not offer extrinsic support but provides intrinsic satisfactions, such as shared pleasure in recreation, relaxation, and uncensored spontaneity, all of which add to quality of life." But people most certainly are not interested in inviting wolves into their families. What has happened is that through selective breeding, people have developed a subspecies of wolf that retains juvenile characteristics throughout life. These eternal wolf puppies see us as the adults in their lives, and yield (sometimes reluctantly) to our authority. As pack hunters, humans and wolves share enough of the basics of social interaction that our behavior is mutually interpretable, and we have found a way to live together.

But I suspect that a visitor from Alpha Centauri would find this situation quite surprising. We actually take the quite non-trivial risk that a predatory animal might maim or kill our children, just to keep it around for yucks and cuddles. That's the just way it is -- it is bedrock in our culture, dogs mean a lot to us, and that's all there is to it.

However, people need to understand that all dogs, even the sweetest tempered, can in fact be dangerous. Yet we take them for granted and treat them far too casually. Most authorities recommend that dogs and children not be allowed together unsupervised, but that is completely alien to our usual practice. Morgan and Palmer write, "Generally, children should be taught to treat dogs with respect, avoid direct eye contact, and not tease them. They should be taught not to approach an unfamiliar dog; play with any dog unless under close supervision; run or scream in the presence of a dog; pet a dog without at first letting it sniff you; or disturb a dog that is eating, sleeping, or caring for puppies." In other words, folks, love them all you want, but that means taking them seriously.

*KPa, KiloPascal, is a unit of pressure equivalent to 1,000 Newtons per Square meter. A Newton is a unit of force equal to the force of earth's gravity at the surface on a mass of 102 grams. An adult of approximately average weight (70 kg) experiences gravitational force of approximately 700 Newtons. 31,790 KPa is a helluva lot of pressure.

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