Humans can get worms from dogs through three main routes: swallowing parasite eggs from contaminated soil or surfaces, skin contact with hookworm larvae in the ground, or accidentally ingesting an infected flea. You don’t catch worms by simply petting your dog. The transmission almost always involves parasite eggs or larvae that have passed through the dog’s feces and developed in the environment, or in the case of tapeworms, a flea that carries the parasite internally.
Roundworms: The Fecal-Oral Route
The dog roundworm is the most well-known zoonotic worm, and the way it reaches humans is surprisingly indirect. Infected dogs shed unembryonated (not yet infectious) eggs in their feces. Those eggs need one to four weeks sitting in soil before they mature into an infectious stage containing larvae. Once they reach that stage, they can survive in the environment for months or even years thanks to a tough protective shell.
Humans become infected by swallowing these matured eggs. This happens most often when contaminated soil gets on your hands and then reaches your mouth, which is why young children who play in dirt and put their hands in their mouths are at highest risk. You can also ingest the eggs through unwashed vegetables grown in contaminated soil or through contact with surfaces where eggs have been deposited.
The important detail here is that fresh dog feces aren’t immediately dangerous for roundworm transmission. The eggs need that incubation period in the environment first. This is why prompt cleanup of dog waste is one of the most effective prevention strategies: removing feces before eggs have time to become infectious breaks the cycle.
What Roundworms Do Inside the Human Body
Humans are accidental hosts for dog roundworms. The larvae hatch in your intestines but can’t complete their normal life cycle, so they wander. They migrate through organs and tissues, causing a condition called visceral larva migrans. Symptoms include fever, coughing, wheezing, abdominal pain, and an enlarged liver.
In some cases, a larva migrates to the eye, causing ocular larva migrans. This typically affects only one eye and can cause redness, seeing spots or flashes of light, a discolored pupil, and in serious cases, vision loss. Children between ages two and seven are diagnosed with this most frequently, likely because of their play habits and hand-to-mouth behavior.
Hookworms: Through Your Skin
Dog hookworms have a completely different entry point. Their larvae don’t need to be swallowed. Instead, they burrow directly through exposed skin. This happens when you walk barefoot or sit on soil or sand contaminated with dog (or cat) feces. The eggs in the feces hatch and release larvae into the ground, where they wait for a host to make contact.
Once hookworm larvae penetrate your skin, they cause a condition called cutaneous larva migrans. You’ll typically see red, intensely itchy, winding tracks under the skin as the larvae tunnel through the upper layers. The tracks move and extend over days because the larvae are literally migrating beneath the surface. Cases are especially common in people who’ve spent time in tropical or subtropical regions where warm, moist soil allows larvae to thrive. Beaches, sandboxes, and shaded backyards in warm climates are common exposure sites.
In rarer cases, hookworm larvae can make it to the small intestine and cause inflammation there, along with digestive symptoms.
Tapeworms: The Flea Connection
The dog tapeworm takes the most unusual route to humans. You can’t get it from touching your dog or from contact with dog feces directly. Instead, you have to swallow an infected flea. Flea larvae eat tapeworm egg packets from the environment. The tapeworm develops inside the flea as it matures from larva to adult. If a person accidentally swallows that adult flea, the tapeworm is released in the intestine and establishes an infection.
Children are the most commonly affected group, likely because of their close face-to-face contact with flea-carrying pets. A child lying on the floor with a dog, or letting a dog lick their face, could inadvertently ingest a flea. This type of infection is generally mild and treatable, but it underscores why flea control on your pets matters for human health too.
Who Faces the Greatest Risk
Children under five are the most vulnerable group, both because of how they interact with the environment (crawling, playing in dirt, touching everything and then their mouths) and because their immune systems are still developing. Adults over 65, pregnant women, and anyone with a weakened immune system are also more likely to develop serious illness if infected.
The behavioral risk factors matter as much as biology. Gardening in soil where dogs defecate, walking barefoot in areas frequented by dogs, and failing to wash hands after handling soil or playing outdoors all increase exposure. Stray and undewormed dogs carry far higher parasite loads. One study found intestinal worm prevalence of about 25% in regularly dewormed pet dogs compared to nearly 79% in dogs that hadn’t been dewormed, and puppies had the highest infection rates of all at roughly 87%.
Practical Prevention
The single most effective habit is picking up dog waste promptly, before roundworm eggs have the one-to-four-week window they need to become infectious. If feces sit in your yard for weeks, you’re building up a reservoir of long-lasting parasite eggs in the soil.
Washing your hands after being around animals, gardening, or playing outside is the other cornerstone. The CDC identifies handwashing as the most important step for preventing zoonotic infections, even if you haven’t directly touched an animal. Roundworm eggs are microscopic and can cling to surfaces, shoes, and garden tools.
For hookworm prevention, wearing shoes and using a towel or blanket when sitting on soil or sand in warm climates eliminates the skin contact larvae need to penetrate. Keeping your dog on a regular deworming schedule dramatically reduces the number of eggs and larvae entering the environment in the first place. And consistent flea prevention on your pets closes the door on the tapeworm route entirely.
Sandboxes deserve special attention if you have children. Covering them when not in use prevents dogs and cats from using them as a litter box, which would deposit eggs right where kids play with their hands.
How These Infections Are Diagnosed
If you suspect a worm infection, your doctor will choose a diagnostic approach based on your symptoms. Hookworm skin infections are often diagnosed visually by the characteristic winding red tracks. Roundworm infections are trickier because the larvae are wandering through organs, not the gut, so standard stool tests may not detect them. Blood tests that look for antibodies to the parasite, along with elevated levels of certain white blood cells, are typically used instead. For eye involvement, an ophthalmologist can sometimes spot larvae directly during an exam.
Tapeworm infections are usually noticed when segments of the worm, which look like small grains of rice, appear in stool or around the affected person’s clothing. Stool examination can confirm the diagnosis.