Hookworms in Dogs: Symptoms, Treatment & Prevention

Hookworms are small intestinal parasites that attach to the lining of the small intestine and feed on blood. In dogs, the most important species include Ancylostoma caninum, Ancylostoma braziliense, and Uncinaria stenocephala. Even though the worms are tiny, they can cause a big problem because they leave bleeding sites behind when they move and reattach.

Some dogs carry hookworms with few outward signs. Others, especially puppies, can become weak, pale, and sick very quickly. A. caninum is especially important because it can cause severe blood loss in young puppies infected through nursing.

Hookworms also matter for human health. Infective larvae in contaminated soil can penetrate skin and cause cutaneous larva migrans, an itchy, winding skin lesion. That is one reason your vet may recommend year-round prevention, regular fecal testing, and fast cleanup of stool in the yard.

Three hookworm species account for nearly all canine infections in North America. Ancylostoma caninum is the most pathogenic and the most common hookworm of dogs in the United States. It predominates in warm, humid regions and is responsible for the majority of clinically significant hookworm disease. Ancylostoma braziliense is found primarily in subtropical and tropical coastal areas, including the Gulf Coast and Florida, and is an important zoonotic species. Uncinaria stenocephala, sometimes called the northern hookworm, tolerates cooler climates and is more prevalent in Canada and the northern United States.

Dogs can become infected through multiple routes. Oral ingestion of third-stage larvae (L3) from contaminated soil, grass, or water is common. Larvae can also penetrate intact skin, particularly through the interdigital spaces and ventral abdomen, a route called percutaneous infection. Dogs that eat paratenic hosts such as rodents or insects carrying encysted larvae may also become infected.

Two additional routes make A. caninum especially difficult to control in breeding dogs. Larvae can undergo somatic migration, traveling through tissues and arresting in skeletal muscle, fat, and other organs in a dormant state called hypobiosis. These arrested larvae can persist for years. During late pregnancy, hormonal changes reactivate dormant larvae, which migrate to the mammary glands and pass to nursing puppies through milk (transmammary transmission). A. caninum is also capable of prenatal (transplacental) transmission, in which reactivated larvae cross the placenta and infect puppies before birth. These two routes explain why puppies can be born infected or develop severe hookworm disease within the first one to two weeks of life, often before eggs are detectable in fecal tests.

Once L3 larvae reach the small intestine, they mature into adults, attach to the intestinal mucosa with their hook-like mouthparts, and begin feeding on blood. A single adult A. caninum can consume approximately 0.1 mL of blood per day, and heavy infections may involve hundreds of worms. Adults shed thousands of eggs daily into the feces. Under warm, moist conditions, eggs embryonate and hatch into first-stage larvae within one to two days, then develop through two molts to the infective L3 stage in five to seven days. The prepatent period, the time from infection to the appearance of eggs in stool, is typically two to three weeks for oral and percutaneous infections, but can be longer when larvae undergo somatic migration before reaching the intestine.

Dogs can pick up hookworms in several ways. They may swallow infective larvae from contaminated soil, water, grass, or dirty paws. Larvae can also penetrate the skin, especially through the feet. Dogs that hunt or eat prey animals may become infected by ingesting larvae in tissues.

Puppies are a special concern. They can be infected while nursing because dormant larvae in the mother can reactivate and pass through milk. That is why very young puppies may become sick before a routine fecal test turns positive.

The life cycle is efficient. Adult worms in the intestine shed eggs into stool. In warm, moist conditions, those eggs hatch and develop into infective larvae in the environment. Once a dog is exposed, larvae migrate through the body and mature in the intestine. Some can become dormant in tissues, which helps explain why reinfection and recurrence can happen even after treatment.

The most common test is a fecal flotation, where your vet checks a fresh stool sample under the microscope for hookworm eggs. Many clinics also use fecal antigen testing or send samples to a reference lab. These tests can improve detection, especially when egg shedding is low.

Timing matters. Hookworms can start feeding before they are mature enough to produce eggs, so recently infected puppies may be very sick even with a negative fecal result. If your dog has pale gums, weakness, or dark stool, your vet may also recommend a complete blood count to look for anemia and sometimes low protein.

If symptoms continue after treatment, your vet may suggest repeat fecal testing, a fecal egg count reduction approach, or a different deworming plan. Drug-resistant A. caninum has been documented in parts of the United States, so persistent positive tests deserve follow-up rather than assuming the medication failed because it was given incorrectly.

Hookworms are one of the most important zoonotic parasites transmitted from dogs to people. When infective L3 larvae in contaminated soil contact human skin, usually bare feet, hands, or buttocks, they can penetrate the epidermis and begin migrating. Because humans are not the natural host, the larvae cannot complete their lifecycle. Instead, they wander through the superficial layers of skin, producing the intensely pruritic, serpiginous (snake-like) tracks known as cutaneous larva migrans (CLM), also called creeping eruption.

A. braziliense is the species most frequently implicated in CLM worldwide, though A. caninum larvae can also cause it. The characteristic raised, erythematous, winding tracks advance a few millimeters to centimeters per day as larvae tunnel through the epidermis. CLM is self-limiting in most cases because the larvae eventually die without reaching the intestine, but the condition can persist for weeks to months and secondary bacterial infection from scratching is common. Treatment with oral ivermectin or albendazole typically resolves symptoms within days.

In rare but well-documented cases, A. caninum larvae have penetrated deeper into human tissues, reaching the intestinal wall and causing eosinophilic enteritis, an inflammatory condition characterized by abdominal pain, diarrhea, and elevated blood eosinophil counts. This ectopic larva migrans has been reported primarily in Australia and the United States. Unlike CLM, eosinophilic enteritis may require endoscopic evaluation and can mimic other gastrointestinal disorders.

The risk of zoonotic hookworm infection is highest in tropical and subtropical regions, on sandy beaches, in playgrounds with sand, and in areas where dogs defecate and the soil remains warm and moist. Children and people who walk barefoot, garden without gloves, or sit directly on contaminated ground are most vulnerable.

Prevention for people includes wearing shoes outdoors in areas where dogs may have defecated, avoiding skin contact with moist sandy soil, washing hands thoroughly after gardening or handling soil, and cleaning up dog feces promptly. Covering sandboxes when not in use and treating infected dogs quickly both reduce environmental contamination.

The CDC has identified multi-drug resistant A. caninum in the southeastern United States as an emerging public health concern. Resistant hookworms that cannot be cleared from dogs with standard anthelmintics lead to prolonged environmental contamination, increasing the zoonotic exposure window for families, neighbors, and community members who share outdoor spaces.

Drug-resistant Ancylostoma caninum is an escalating problem in veterinary parasitology. Reports published since 2019 have documented A. caninum populations resistant to all three major anthelmintic drug classes used in dogs: benzimidazoles (fenbendazole, febantel), tetrahydropyrimidines (pyrantel pamoate), and macrocyclic lactones (ivermectin, milbemycin oxime, moxidectin). Multiple-drug resistance, where a single hookworm population is resistant to two or all three drug classes simultaneously, has been confirmed in multiple studies.

The problem was first recognized in racing greyhound colonies, where dogs were housed in densely populated kennel environments and dewormed frequently with the same drug classes for years, creating strong selection pressure for resistant genotypes. When retired racing greyhounds were adopted into pet homes, they carried resistant hookworm populations into communities. Subsequent studies have confirmed that resistant A. caninum is no longer confined to greyhounds; it has been documented in pet dogs of various breeds, predominantly in the southeastern United States but with cases reported in other regions as well.

Clinically, drug resistance should be suspected when a dog remains positive for hookworm eggs on fecal flotation after completing an appropriate course of a correctly dosed anthelmintic. The fecal egg count reduction test (FECRT) is the primary diagnostic tool for confirming resistance. A FECRT compares the fecal egg count before treatment with the count 10 to 14 days after treatment. A reduction of less than 90 to 95 percent suggests resistance to the drug used.

The Companion Animal Parasite Council (CAPC) has issued guidance on managing suspected resistant hookworm infections. Recommendations include confirming resistance with FECRT, switching to or combining anthelmintic drug classes, using an adulticide in combination with a macrocyclic lactone preventive (for example, treating with febantel-pyrantel-praziquantel plus maintaining monthly moxidectin), and performing serial fecal monitoring every two to four weeks. Aggressive environmental decontamination, including removal of feces at least daily and restricting the dog to hard, cleanable surfaces when possible, is critical for breaking the reinfection cycle.

Eradication protocols using combination therapy with multiple drug classes administered on an accelerated schedule have been described in the veterinary literature and may offer improved clearance rates. However, no single approach has been shown to reliably eliminate all resistant infections, and long-term follow-up with repeated fecal testing is essential. The development of new anthelmintic compounds and novel formulations is an area of active research, but no new drug classes for canine hookworms have reached the market as of early 2026.

Dog owners in endemic areas should discuss hookworm prevention and monitoring strategies with their veterinarian, avoid purchasing deworming products without veterinary guidance, and report any persistent infections so that appropriate resistance testing can be pursued.

Prevention works best when it is layered. Year-round broad-spectrum parasite prevention is the backbone because many monthly heartworm preventives also treat or control hookworms. Your vet can help match the product to your dog's age, lifestyle, and other parasite risks.

Routine fecal testing still matters, even for dogs on prevention. Dogs can miss doses, spit out medication, or become reinfected from contaminated environments. Puppies usually need more frequent deworming and stool checks because they are more vulnerable and may be infected through nursing.

At home, pick up stool promptly, keep runs and yards as clean and dry as possible, and avoid letting dogs rest or dig in heavily contaminated areas. Wear shoes outdoors, wash hands after handling soil or stool, and supervise children around areas where dogs eliminate. These steps help protect both your dog and your family.