"My dog has worms — how do I treat it and is it contagious to humans?"

Why dogs get worms — and what they're actually doing inside

The word "worms" covers several distinct parasites that live in your dog's intestinal tract — most commonly roundworms, hookworms, tapeworms, and whipworms. Each has a different life cycle, transmission route, and set of symptoms, which is why the blanket term can be misleading. Roundworms are the most prevalent, especially in puppies; they look like spaghetti strands and are often passed from mother to pup before birth or through nursing. Tapeworms are acquired by swallowing an infected flea — a single flea ingested during grooming is enough — and show up as rice-like segments around the tail. Hookworms are microscopic blood-feeders that can penetrate skin directly from contaminated soil, and whipworms live in the large intestine and are picked up from soil or feces.

What makes worms particularly insidious is that many dogs show no outward signs at all, especially in the early stages of infection. When symptoms do appear — a pot-bellied look, dull coat, weight loss despite eating normally, scooting, diarrhea, or visible segments in the stool — the infection is often already well-established. Puppies and immunocompromised dogs tend to show symptoms more dramatically; healthy adult dogs can carry significant worm burdens for weeks before you notice anything wrong.

The diagnosis is confirmed with a fecal flotation test — your vet mixes a small stool sample with a solution that causes worm eggs to float to the surface, where they can be identified under a microscope. This matters because different worms require different dewormers, and treating with the wrong one wastes time and money while the infection continues.

Dog worms don't all look — or behave — the same way

Your situation will shape which worm is likely responsible and what the right next step is. Pick the description that fits your dog most closely.

What happens if dog worms go untreated — to your dog and your family

For most healthy adult dogs, a moderate worm burden won't be immediately life-threatening — but it won't resolve on its own either. Worms reproduce, the infection deepens, and over weeks to months you'll see progressive weight loss, nutritional deficiency, anemia (especially with hookworms), and immune system suppression that makes your dog vulnerable to other illnesses. In puppies, severe roundworm or hookworm infections can be fatal. Tapeworms are less immediately dangerous but cause chronic discomfort and won't clear without the right treatment. The earlier you treat, the less damage is done.

The human risk is real but manageable. Roundworm larvae can migrate through human tissue — a condition called visceral larva migrans — causing fever, fatigue, and in rare cases affecting the eyes or nervous system. Hookworm larvae from contaminated soil can penetrate bare human skin (cutaneous larva migrans), causing an intensely itchy, winding rash. Children who play in soil where dogs defecate are at the highest risk. Tapeworms can technically infect humans but only if you accidentally swallow an infected flea — it's uncommon. Whipworms do not infect humans at all.