My Flu Prevention Advice

by Amy Fernandez

Flu season is here. In case you momentarily forget that fact, every news report features helpful recommendations to ward off the virus by strengthening your immune system. Drinking tea, taking vitamins, and eating garlic offer debatable immunological protection. But this year, a new tip has appeared on this obligatory list of flu prevention advice- GET A DOG! A widely cited study suggests that contact with dogs triggers damn good immune function.

This surprising fact was uncovered by Dr. Eija Bergroth, a pediatrician at Finland’s Kuopio University Hospital. Between September 2002 and May 2005 Bergroth and her colleagues tracked the health of 397 children throughout their first year of life. They were enrolled in this study prior to birth and it’s particularly significant for that reason. As dog breeders know, the immune system requires several months to mature and become fully functional as passive immunity wanes and the body begins producing its own antibodies.

Although this study focused on a very small group of children, Kuopio is a recognized leader in the fields of health care, pharmacology , environmental science, and nutrition. And perhaps they weren’t looking for these results when they embarked on this particular research.

Babies who had close contact with a dog during their first year were 31 percent more likely to be healthy and those in homes with a cat were 6 percent less prone to illnesses. Overall, babies in homes with pets were 44 percent less likely to develop common childhood ear infections and 29 percent less likely to receive antibiotics. These results defy conventional wisdom. An immature immune system predisposes an individual to a host of opportunistic infections. Therefore, it seems logical to keep the environment as clean and sterile as possible. Of course, for most parents that’s easier said than done, especially in homes with multiple children and pets. Like puppies, kids don’t hesitate to explore and taste anything interesting that comes their way, thus introducing pathogens that might never enter the picture when they are older and more discerning. There might be an evolutionary justification for this alarming behavior.

This wasn’t the first study to conclude that low level exposure to common pathogens gives the immune system a valuable workout as matures. These challenges also mobilize its regulatory response and fine tunes its ability to respond appropriately to the millions of microbes we routinely encounter. In other words, it learns the difference between harmful and harmless microbes, and knows when to call 911 . The Finnish study clearly showed that early exposure to pets lowered a child’s risk of developing allergies and asthma.

But that wasn’t all. Modern society’s obsession with ultraclean environments and antibacterial products is based on sound scientific principles. But overreliance on this strategy encourages antibiotic-resistant strains of disease-causing pathogens. Microbes always seem to stay a step ahead of our efforts to kill them off.

On the other hand, limited exposure to common germs activates a primary immune response. Fighting an infection triggers the production of neutralizing antibodies. After recovery, they remain in the bloodstream, ready for action whenever they encounter similar pathogens. Depending on the diseases, this immunological memory can persist for a few months or a lifetime. And don’t underestimate the defensive capability of naturally acquired immune response. It has kept us ahead of nature’s microbial arms race for thousands of years.

A smorgasbord of infectious disease pathogens emerged hand in hand with human civilization. The concurrent rise of civilization and disease had a crucial common denominator, the presence of numerous wild species that were easily domesticated. After a few thousand years of upclose personal contact with domestic animals their pathogens inevitably adapted to new hosts and vectors and jumped the species barrier. Of the 1,415 documented pathogens known to infect humans, 61 percent are classified as zoonotic. This doesn’t include old favorites that abandoned their former hosts to become strictly human diseases, like measles, smallpox, influenza, diphtheria, tuberculosis and cold viruses to name a few.

Pigs, ducks, and chickens can be thanked for various strains of influenza. Measles, smallpox, distemper, and tuberculosis came to us courtesy of cattle. The measles virus diverged from rinderpest around the 11th or 12th century- and it was equally contagious. Before the advent of vaccines over 90 percent of children became infected with it by age 15. Of course, livestock guaranteed an abundant food supply and a rising population density, which was the basic recipe for disease epidemics. We are very familiar with that part of the story, along with the breakthroughs in germ theory and basic sanitation measures that got them under control.

However, historians often overlook another critical factor in this equation. Thousands of years of contact with domestic animals also fostered disease tolerance in these populations. This is a very slow defensive response, but natural selection gradually changed gene frequencies to create a degree of genetic immunity to particular pathogens.

This theory was first proposed by B. S. Haldane in the 1940s in conjunction with his research on malaria. According to Haldane’s hypothesis, resistance alleles to certain pathogens emerge in various populations. These genetic variants are inheritable and become more prevalent over the course of generations. This explains why previously unexposed individuals develop tolerance for potentially lethal diseases that were endemic in many civilizations.

genetically based disease resistance spread throughout many human populations over the last millennium. For instance, smallpox first appeared in Egypt around 1600 BC. Countless smallpox epidemics decimated Europe between the 4th-15th centuries. By the late eighteenth century it was still killing approximately 400,000 Europeans annually. But after thousands of years, they possessed a degree of genetic resistance, and it was far less deadly. Another ancient disease, lassa fever, continues to infect millions of West Africans. But researchers have documented natural resistance to the virus in 50 to 90 percent of the population of several affected West African countries. These were endemic, lethal diseases, but their virulence abated as populations developed genetic resistance.

In contrast, when a new pathogen was introduced into a population, all hell broke loose. In the 1300’s, Mongol invaders from Central Asia transmitted the bubonic plague to Europe. Within a couple of hundred years, the Black Death killed a third of Western Europe’s population. Europeans, Asians, and Africans had some natural resistance to Old World endemic diseases when these pathogens hit North America in the 1500s. These civilizations were promptly decimated by smallpox, measles, typhoid, diphtheria, tuberculosis, and influenza. Estimated mortality rates range from 70-95 percent. Although it’s small consolation, current theory suggests that they repaid the favor by sending syphilis back to Europe where the population possessed absolutely no immunity to this little gem.

The sad fact is that daily life translates into a continuous bombardment by millions of microbes. Some familiar and some brand new. Our amazing immune system has multiple strategies to keep us ahead of the game and science is just beginning to understand them. For instance, well documented evidence confirms the emotional benefits of pet ownership and its correlation with physical health. This helps to explain why dog people never seem to get sick. Well, technically we do, but we seem to have an amazing capacity to overcome health challenges. We often attribute this to our innate toughness. We get out of bed to feed our dogs when we are deathly ill with the flu and gamely limp off to shows with just about any injury short of fatal. Our dogs definitely motivate us to keep going. And now we have proof that contact with animals improves our immune function. Hey….in few thousand years dog people will probably be immune to almost everything.

Thankfully, vaccines came along to jumpstart this process and prevent many contagious diseases in both humans and animals. Inducing immunity through vaccination had been practiced in China and India for centuries before Edward Jenner made his breakthrough discovery in 1796. Earlier methods utilized direct exposure to minute quantities of the causative agent. Because of the close genetic relationship between human and animal pox strains Jenner’s technique of using cowpox virus to inoculate against smallpox was significantly safer and more effective. It was the first of many discoveries that got this killer under control. The last recorded smallpox endemic occurred in Somalia in 1977, and the last human infection was due to a laboratory accident in England in 1978. In 1980, the World Health Organization officially declared smallpox eradicated. The last confirmed case of rinderpest was diagnosed in 2001, and it became second disease in history to be eradicated through comprehensive vaccination programs in 2011.

Vaccinations have saved millions of lives. Never take them granted. So get your flu shot, and just to be sure that your immune system is running on all cylinders, give all your dogs a nice big hug and a kiss.

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Posted by admin on Jan 22 2013. Filed under Current Articles, Featured. You can follow any responses to this entry through the RSS 2.0. Both comments and pings are currently closed.