Pet Parasites: A Danger to Human Health

Why should I care about my pets’ worms?

Hidden from view, the intestinal parasites of our pets don’t share the spotlight given to fleas or even mosquitoes. In fact, many pet owners would just as soon forget that their pets could be carrying these “worms”. People, especially children, can get infected with worms directly from our pets so this is not a problem to be ignored.

How do our pets get worms?

Most people don’t realize it, but almost all puppies and kittens are born with roundworms, hookworms or even both. In the vast majority of cases, these worms are passed from mom to the babies either during pregnancy or during nursing after birth. Left unchecked, these tiny monsters can cause poor growth, diarrhea, vomiting, or even death in young animals.

Your vet will regularly worm kittens and puppies to kill these parasites that were passed down from mom.

Adult pets aren’t immune to these parasites either. Pets who consume other animals’ feces, eat grass, or even those who catch and eat infected rodents might end up with bloody, runny stool or vomiting caused by the worms.

A dog or a cat can pick up roundworm or hookworm eggs by digging or just walking on dirt or grass where another dog or cat defecated. The feces can be long gone but the eggs remain in the soil over years of heat and frost. Once ingested roundworm larva migrates through the liver and lungs on the way to the dog or cat intestine. The larva can be coughed up and be in the saliva of your pet and transmitted when they lick you.

How do people get worms?

Pets share our homes, our kitchens, and, in some cases, even our beds. Unfortunately, they might also be sharing some unwanted guests – WORMS! Unlike fleas and mosquitoes who sometimes give us a break during colder weather, these parasites can cause problems all year long!

But beyond their immediate effects on the animals, there is an even more sinister side to these pests. Both roundworms and hookworms are zoonotic, meaning that they can be passed to humans. Children are especially susceptible and can suffer blindness, seizures or organ dysfunction. In extreme cases, young children have lost an eye to roundworm infections.

Humans are not the end host so worms wander around in us not knowing where to go. They can end up in our eyes and migrate through our body. Hookworm larva migrate just under our skin and a serpentine line can be seen and it migrates over time under the skin. Disgusting? Yes!!!

At our practice, we biopsied a bump on a dog’s nose and the pathologist returned a report stating the lump was an encysted roundworm larva. That’ s proof that our dogs and cats can cough up a migrating larva, lick us and transmit the disease to us. Once I was explaining the parasite life cycle to one of our clients and she told me she absolutely knew about the life cycle because her sister had lost an eye to the parasite. Ophthalmologists find them swimming in the vitreous humor, or liquid part, of the eye.

Why aren’t we aware of this danger?

The Centers for Disease Control (CDC) estimates that almost 14% of the U.S. population is infected with roundworms. That’s nearly 40 million people!

The answer lies in the life cycle of these parasites. After the larval worms make their way to the puppies’ digestive tract, they mature into adults over a 3 week period of time. Then, the real danger begins. Adult female worms begin shedding enormous numbers of eggs into the environment. It’s not unusual for more than 200,000 eggs to be shed every single day by a single female.

Now, imagine a mother dog with a litter of 9 puppies. Including mom’s contribution, even if each pup had only one female worm, more than 2 million eggs are being deposited daily into the yard where the puppies…and your kids, play. Multiply that by the number of days until the pups get an initial de-worming and you can see why this is a problem that has not gone away.

Thankfully, hookworm eggs are often killed by freezing temperatures, but in areas of the Southeastern U.S., hookworm larva can survive in sandy soil, emerging to penetrate the bare skin. In people, this infection causes an intense itching sensation along with redness and swelling along the migratory track of the hookworm larva. Dogs often present with hair loss on all four feet and thickened, damaged skin on the lower legs.

Due to the prevalence of these worms in our pets, the Companion Animal Parasite Council (CAPC, has developed “strategic de-worming” protocols as a means to help protect both people and pets. Starting with puppies and kittens, CAPC recommends providing a de-worming medication every 2-3 weeks from two weeks of age until 12 weeks. In addition, pet owners are urged to contact their veterinarian for a recommendation on the proper monthly parasite prevention product that contains medication to control these intestinal parasites. Many of the products control heartworm and the parasites that spread to humans. Both dogs and cats should take one of these products every month, all year round! It’s a safe and easy way to protect the whole family! Instead of forgetting the medication in the drawer set up an alert for yourself monthly to give the medication. If you need a visual cue the products come with stickers you can place on a calendar.

Parents should teach children to wash their hands after playing with the pets or playing in the yard where pets defecate. Since the eggs are microscopic, you won’t see any evidence in the kid’s hands, but a thorough washing will help ensure these parasites won’t end up infecting your children. Ideally, the pet waste is picked up regularly in the yard.

It’s also a good idea to check your pet’s stool sample routinely. The short life cycle of these parasites means that a severe infestation can occur quickly. Also, many other parasitic worms and protozoans pose some danger to our pets and these can all be found with a routine fecal sample. Your veterinarian can help you determine how often to test your pet’s stool-based on previous exposure and geographic area.

Our pets are a big part of our lives and we want to share as much as we can with them. Playing it safe and following your veterinarian’s guidelines for de-worming could mean that you can share a much longer, healthier life together

Dr. Elizabeth Bradt is a 1986 graduate of Tufts University Cummings School of Veterinary Medicine and is owner of All Creatures Veterinary Hospital in Salem MA

E-mail your pet questions, experiences you’ve had with your pet at [email protected]. Please title your e-mail Vet Connection.