Hookworms spread easily between dogs, though not through direct contact like a cold or flu. Instead, one infected dog contaminates the environment with hookworm eggs in its feces, and other dogs pick up the infection from that contaminated soil, grass, or sand. The larvae can survive in favorable conditions for three to four weeks, turning any shared outdoor space into a potential source of infection.
How Hookworms Spread Between Dogs
Dogs don’t pass hookworms to each other nose-to-nose. The cycle works through the environment. An infected dog sheds microscopic hookworm eggs in its stool. In warm, moist, shady conditions, those eggs hatch into larvae within one to two days. Once hatched, the larvae sit in the soil waiting for a new host.
A second dog can become infected in two main ways. The most common is swallowing larvae while sniffing, licking, or eating contaminated soil or grass. The second is skin penetration: larvae can burrow directly through the skin of a dog’s paws or belly when it lies on infested ground. Both routes lead to an active infection as the larvae migrate through the body and eventually settle in the intestines, where they latch onto the intestinal wall and feed on blood.
There’s also a third route that matters specifically for puppies. An infected mother dog can pass hookworm larvae to her nursing puppies through her milk. This transmammary transmission is one reason hookworm infections hit puppies especially hard, sometimes before the puppies are even old enough to go outside.
Why Puppies Are at Greatest Risk
Hookworm infections in young puppies can be severe and even fatal. Because the parasites feed on blood (a single worm can consume up to 0.1 mL of blood per day, and infections often involve dozens or hundreds of worms), puppies can develop serious anemia rapidly. The earliest sign is often pale gums, followed by weakness and dark, tarry diarrhea. Puppies that survive develop some immunity over time, but malnourished or debilitated animals may struggle with chronic anemia, poor growth, and weight loss well beyond the initial infection.
This vulnerability is why veterinary guidelines recommend starting deworming treatment as early as two weeks of age, then repeating it every two to three weeks until puppies are at least eight to twelve weeks old. Re-treatment is critical because deworming medications kill adult worms in the intestines but don’t always reach larvae still migrating through other tissues. Those larvae mature into new adults over the following weeks, requiring another round of treatment to clear them.
Signs of Hookworm Infection in Dogs
Symptoms depend on how heavy the infection is and how old the dog is. In adult dogs with a mild infection, you might not notice anything obvious. As the worm burden increases, common signs include:
- Dark, tarry stools caused by digested blood from intestinal bleeding
- Diarrhea that may come and go or persist
- Weight loss and poor appetite
- Weakness and lethargy from progressive anemia
- Dull, dry coat
- Irritated paws in cases where larvae entered through the skin
The bleeding happens because hookworms physically attach to the intestinal lining and feed, then shift to new feeding sites, leaving behind small ulcerations that continue to bleed. In severe cases, especially in puppies, the anemia progresses quickly from mild to life-threatening.
Hookworms Can Also Infect Humans
This is the part many dog owners don’t expect. Hookworm larvae in contaminated soil can burrow into human skin too, typically through bare feet or any exposed skin that contacts infested ground. The CDC notes this commonly happens when people walk barefoot or sit on contaminated soil or sand.
In humans, dog hookworm larvae usually can’t complete their full life cycle. Instead, they get trapped in the skin and cause a condition called cutaneous larva migrans: intensely itchy, raised red lines or tracks that creep across the skin as the larvae tunnel beneath the surface. The symptoms resolve on their own after several weeks as the larvae die, though treatment can speed relief. In rare cases, certain hookworm species may penetrate deeper into the intestine, lungs, or eyes.
The practical takeaway: if your dog has hookworms, pick up feces from your yard promptly, wear shoes outdoors, and avoid sitting on bare ground in areas where infected dogs have been.
Diagnosis and Treatment
Veterinarians diagnose hookworms through a fecal flotation test, which detects eggs in a stool sample under a microscope. One limitation is timing: newly infected dogs may not shed eggs for several weeks after infection (the “pre-patent period”), so a negative test doesn’t always rule out hookworms if symptoms are present. Repeat testing may be needed.
Treatment involves deworming medications. The most commonly used options include pyrantel (often the first choice for puppies because it’s safe at very young ages), fenbendazole (which also covers whipworms and some tapeworms), and ivermectin-based products. A single dose kills the adult worms currently in the intestines, but a follow-up dose two to three weeks later is essential to catch any larvae that have since matured into adults.
One growing concern is drug-resistant hookworms. Multi-drug resistant strains of the most common dog hookworm have been confirmed across multiple breeds and regions in the United States, no longer limited to greyhounds where they were first identified. If a dog’s hookworm infection doesn’t clear after standard treatment, your vet may need to adjust the approach or use combination therapies.
Preventing Reinfection
Because hookworm larvae can persist in soil for weeks, clearing an active infection is only half the battle. The Companion Animal Parasite Council recommends year-round broad-spectrum parasite prevention for all dogs. Many monthly heartworm preventives also contain ingredients that protect against hookworms, making this a straightforward addition to routine care.
Fecal testing should happen at least four times during a dog’s first year of life, then at least twice a year for healthy adults. Dogs with higher exposure risk (those who spend a lot of time outdoors, visit dog parks, travel, or live in warm, humid climates) may need more frequent screening.
Environmental management makes a real difference. Pick up your dog’s stool daily, since eggs need one to two days in the soil before they hatch into infectious larvae. Prompt removal breaks the cycle before new larvae ever develop. Avoid letting dogs roam in sandy, shaded areas with poor drainage, which are ideal conditions for larvae survival. If you have a yard where an infected dog has been, keep in mind that larvae already in the soil can remain infectious for three to four weeks, so continue to exercise caution with bare skin contact during that window.