Zoonotic Disease Transmission

Good Hygiene is Essential but other Humans are the Greatest Risk


When the Europeans came to America they brought diseases that we as a people only scarcely survived. Because of the Europeans’ close association with their animals they were immune to most of the diseases that we were not. My question: A lot of people kiss and do other questionable things with their animals, the animals kiss and lick other animals’ butts and parts, is this how diseases were and still are transmitted to humans?


Dr. Nichol:

Zoonotic diseases are central to our concerns about worldwide epidemics. There are about 150 infections shared between humans and other species. Most are spread orally or by bites, scratches, or carrier insects. Infectious organisms are pretty much everywhere; failing to wash your hands before eating puts you at risk even if you don’t interact with animals.


It’s been in just the last several hundred years that zoonotic epidemics have become a serious problem. In the days of nomadic tribes human populations were small and rodents and mosquitoes didn’t accumulate in great enough numbers to carry out much damage. As communities grew, vulnerable populations started getting sick because of their contact with animals.


By the Middle Ages there were hoards of rodents in European cities feeding on garbage. Along with their fleas they spread plague, wiping out huge numbers of humans. When the Spaniards came to this continent with their infectious diseases everything changed for the Native Americans. The indigenous peoples had no natural protection against infections like smallpox and measles. But by then these viruses had long outlived their link with animals.


In those days it was minor exposure to contagious organisms that stimulated natural immunity in the lucky ones who survived these epidemics. Today we have vaccines but now there are new infections, some involving domestic animals. Human fetuses, children, and the elderly are especially vulnerable to intestinal parasites of pets. But that’s only part of the story. Wildlife has always served as a reservoir of infectious diseases.


In our modern world people and livestock are constantly on the move, never mind vectors (carriers) like exotic species of mosquitoes traveling the world in cargo ships. Our society is rightly concerned about terror threats but the rapid spread of infections like West Nile virus, swine flu, avian influenza, SARS, and Lyme disease has the potential of much greater devastation.


The truth is that the greatest infectious disease risk faced by any of us is not from animals but members of our own species. There’s a lot you can do to stay healthy. I agree that animals kissing and licking butts and other parts is disgusting. Just don’t hang out with people like that. If you love your pets despite their questionable hygiene have them checked annually for parasites and for cryin’ out loud wash your hands before eating that sandwich.