What exactly are hookworms and how do they infect a dog?

Canine hookworms are small nematodes, most commonly Ancylostoma caninum in the United States, that live attached to the wall of the small intestine using hook-shaped mouthparts and feed directly on the dog's blood (Merck Veterinary Manual, 2023). A single worm is only about 2 to 3 millimeters long, so infected dogs rarely show visible worms in their stool, which is one reason infections go unnoticed until blood loss becomes significant. Adult female hookworms are prolific egg producers, and those eggs pass in feces and hatch into infective larvae in warm, moist soil within days.

Dogs pick up hookworm larvae in several ways: swallowing larvae from contaminated soil or bedding, larvae actively penetrating the skin (often between the toes), nursing puppies ingesting larvae in their mother's milk, or larvae crossing the placenta before birth (Companion Animal Parasite Council, 2023). Because transplacental and transmammary transmission are so common, puppies can be born already infected or become infected within their first weeks of life, which is why veterinarians recommend deworming puppies starting at 2 weeks of age regardless of visible symptoms.

What are the first signs an owner usually notices?

In puppies, the earliest signs are often nonspecific: poor weight gain, a dull coat, soft or dark tarry stool, and lethargy that owners may initially chalk up to normal newborn sleepiness (American Kennel Club, 2022). Because hookworms feed on blood, pale gums are one of the more telling early clues, especially in litters where multiple puppies are affected at once and one or two seem weaker than their littermates.

Adult dogs frequently show milder or no symptoms because they've built partial immunity from prior exposure, but chronic low-level infection can still cause intermittent diarrhea, weight loss, and a poor coat over months (Cornell Riney Canine Health Center, 2022). Skin irritation, itching, or redness between the toes can also appear when larvae penetrate the skin directly rather than being swallowed, a route called percutaneous infection.

Why do puppies get so much sicker than adult dogs?

A heavy hookworm burden in a young puppy can cause severe iron-deficiency anemia because puppies have a much smaller total blood volume to begin with, and continuous blood loss from dozens of feeding worms can outpace their ability to regenerate red blood cells (Merck Veterinary Manual, 2023). Veterinary literature documents cases of neonatal puppies dying from acute blood loss anemia within the first few weeks of life when transplacental or transmammary hookworm burdens are high.

Risk factors that make infection more likely include living in warm, humid climates where larvae survive longer in soil, crowded or unsanitary whelping conditions, shelter or stray backgrounds, and lack of consistent monthly parasite prevention (Companion Animal Parasite Council, 2023). Dogs housed on dirt or grass runs that aren't regularly cleaned face repeated re-exposure even after successful treatment, since larvae can remain infective in shaded, moist soil for weeks to months.

How do veterinarians actually confirm a hookworm diagnosis?

The standard test is a fecal flotation, in which a stool sample is mixed with a special solution that causes hookworm eggs to float to the surface, where they're identified under a microscope; many clinics also run fecal antigen ELISA tests that can detect infection even when egg shedding is low or intermittent (American Animal Hospital Association, 2018). Because egg shedding can be inconsistent, veterinarians sometimes recommend repeating the fecal test if a heavily symptomatic dog initially tests negative.

For puppies showing signs of anemia, vets typically pair the fecal exam with a complete blood count to check red blood cell counts, hemoglobin, and hematocrit, which helps gauge how urgently treatment and possibly a blood transfusion are needed (Merck Veterinary Manual, 2023). The Companion Animal Parasite Council recommends fecal testing at every puppy visit and at least annually for adult dogs, since hookworm shedding can be sporadic even in truly infected animals.

What treatment will the vet actually prescribe?

Treatment centers on an oral dewormer such as fenbendazole or pyrantel pamoate, which kills adult worms in the intestine; because these drugs don't reliably kill larvae that are still migrating through tissue, veterinarians typically prescribe a repeat dose 2 to 4 weeks later to catch newly matured worms (Companion Animal Parasite Council, 2023). Puppies are commonly started on deworming medication at 2, 4, 6, and 8 weeks of age specifically because of how common in-utero and nursing transmission is.

Severely anemic puppies may need supportive care beyond deworming, including iron supplementation, a high-quality diet to rebuild red blood cells, and in critical cases a blood transfusion before the parasite burden can even be safely addressed (American Kennel Club, 2022). Because reinfection is common, most veterinarians pair initial treatment with a monthly heartworm preventive that also controls hookworms, such as products containing milbemycin oxime or moxidectin, to prevent the cycle from restarting.

How can I keep my dog from getting reinfected at home?

Because hookworm eggs need warm, shaded, moist soil to develop into infective larvae, prompt removal of feces from yards, especially within 24 hours, significantly reduces environmental contamination and reinfection risk (Companion Animal Parasite Council, 2023). Concrete or gravel runs are easier to disinfect than dirt or grass, and diluted bleach solutions can help kill larvae on hard, non-porous surfaces, though soil contamination is much harder to fully eliminate once established.

Monthly broad-spectrum parasite preventives that cover hookworms year-round are the most reliable long-term defense, and the Companion Animal Parasite Council recommends keeping dogs on these products continuously rather than seasonally, since larvae can persist in soil even through cooler months in many regions (Companion Animal Parasite Council, 2023). Routine annual fecal testing, even in dogs without symptoms, catches low-level reinfections before they progress to clinical illness.

Can hookworms in my dog make people in the house sick?

Yes — canine hookworm larvae can penetrate human skin and cause a condition called cutaneous larva migrans, producing itchy, winding, raised red tracks on the skin, most often on the feet or lower legs after walking barefoot on contaminated soil or sand (Centers for Disease Control and Prevention, 2021). Children are at higher risk because of more direct ground contact during play, and infections are more frequently reported in warm, humid climates including parts of the southeastern United States.

The CDC recommends wearing shoes on soil or sand where dogs defecate, washing hands after handling soil or a dog's stool, and promptly treating infected dogs to reduce environmental larval contamination (Centers for Disease Control and Prevention, 2021). While the larvae generally can't complete their life cycle in human tissue and the skin lesions typically resolve on their own or with anti-parasitic treatment, prevention through good sanitation and prompt pet deworming remains the most effective safeguard.