Even the thought of worms inside your dog is pretty sickening, but with TV shows like Monsters Inside Me creating alarm, I get questions like “Can my dog give me worms?” a lot. If I go into the exam room with a new puppy and announce the results of my fecal exam to a mom and kids, for example, the mom’s eyes often widen as she glances at her children cuddling the puppy.
When I was little, my mother did not like us to let the dog lick our faces, and this fear was probably part of the reason why. So when your dog licks your face, should you be afraid?
First of all, there are parasites that are found in dogs that can infect humans (maybe not exactly in the way you think) but it is true. Worms have evolved to live inside their hosts. They want to live and to thrive so that they can produce offspring that can be passed on to the next viable host. The most successful parasites do not kill their hosts, at least not before the host can assist them in propagating their species.
I think that people think they can catch intestinal worms from pets and that these worms will similarly infect their GI tracts, causing mild to no symptoms and then be easily removed with no permanent issues. The common zoonotic parasites infect people in ways different from pets and it is not simple or harmless.
Zoonotic (animal to human transmission) diseases are an important issue in the public health.
Roundworms
Roundworms (Toxocara spp.) are a zoonotic risk. Roundworms become a threat when the eggs are ingested from a contaminated environment, not typically from an infected dog licking faces. Small children who put environmental items or soil in their mouths are most at risk. Because human beings are not an ideal host for the larvae, they tend to migrate away and not settle in the gastrointestinal tract like they would for dogs. These migrations can be in multiple organs and since the worm is not adapted for life outside the GI tract, the migrations are extremely destructive. They have been known to cause permanent blindness when they migrate in ocular tissue and multiple other organ systems may be damaged depending on where the larvae travel. Make sure your dog is on a regular deworming program that covers roundworms to protect you both.
Hookworms
I see lot of puppies infected with hookworms. These worms are a zoonotic threat and cause a severely itchy skin migration called cutaneous larval migrans. At my first job out of school, I will never forget one of the senior clinicians telling a story. Somehow he had been recruited to help with a surprise puppy delivery in a seamy part of town. He said that he remembers that he was wearing really nice shoes and the lot where the mother dog was struggling was deep in mud. He wanted to help the dog, but not ruin his shoes so he stripped off his nice shoes and socks and waded into the mud barefooted. I recall his sheepish grin as he told about the cutaneous larval migrans that he developed on his feet from the hookworms in that mud. Hookworms can also cause organ migrations (although less commonly than roundworms) that can be very dangerous.
The moral of that story is not that veterinarians should never wear nice shoes (although I have ruined a few). It is that all dogs should be carefully and regularly dewormed. All animal lovers must remember that moist soil can harbor parasites and the soil where your dog lives is more of a threat than the actual dog. Wear shoes in the soil and gloves when you garden and discourage small children from putting soil or objects in their mouths.
Can your dog give you worms?
Technically, yes. But stray dogs and cats that are not routinely dewormed and defecate in soil of your environment are a much greater risk. Remember, deworming is an ongoing maintenance. Deworming one time will not cover your dog forever. Worms are ubiquitous. Much like you wouldn’t think that changing the oil in your car is a one-time only process, your dog must be regularly dewormed according to your vets recommendations.
