Dogs with hookworms

Veterinarian injecting small dog in a clinic

Hookworms are a kind of intestinal parasite that feeds on blood. They are widespread in dogs. While the majority of infections are not fatal, they can cause chronic anemia and sometimes fatal blood loss in pups. There are various hookworm species that afflict dogs, with Ancylostoma caninum being the most frequent in North America. Humans can be infected with hookworms, although they seldom cause major issues.

What Are Hookworms?

Hookworms are little parasitic worms with hook-like teeth or mouth plates that are less than one inch long. These structures aid in their attachment to their animal hosts' intestinal walls, where they feed on blood.

Hookworms stick to the intestinal wall and feed on blood and/or tissues, unlike roundworms, which float around in the intestines stealing nutrients from a dog's meals. They can detach and migrate to new locations, leaving little bleeding sores where they previously fed.

Symptoms of Hookworms in Dogs

Hookworms can produce any of the following symptoms, but overt signs may only appear with heavy infestations:


  • Failure to gain weight or weight loss
  • Loss of appetite
  • Diarrhea
  • Bloody or black stools
  • Anemia (pale gums, weakness)
  • Coughing, due to the larval migration through the lungs (with very heavy parasite load)
  • Skin irritation, most often on the feet between the toes, due to burrowing larvae

Hookworm symptoms are caused by the worms' unpleasant presence in the intestines, as well as blood loss from their eating. Blood loss in the upper intestines is indicated by black or tarry stools, but bleeding in the lower intestines is indicated by red blood.

Causes of Hookworms

Hookworm eggs are passed in animals' feces. After several days and under warm, moist conditions, the eggs hatch into larvae. These larvae have several ways they can infest dogs:

  • They can be ingested directly, as when dogs lick the ground or groom themselves when larvae are present on their fur.
  • They can migrate through the skin, usually through the belly or paws.
  • They can be ingested by another animal such as a rodent, and then be ingested by a dog that eats the infected animal.
  • Puppies can also be infected by larvae present in their mother's milk.

Hookworm larvae may grow into adult worms in the intestines of a dog once they have been introduced. They can also move through the dog's tissues to the lungs, where they are coughed up and ingested, before maturing into adults in the intestines. Migrating hookworm larvae usually reach a latent stage within bodily tissues in elderly dogs before becoming mobile again.

Because the larvae become active during pregnancy, they are frequently passed on to puppies. Hookworm larvae can enter the mammary glands in some cases. Others mature into adults in the mother's intestines, producing eggs that infect puppies.

Diagnosing Hookworms in Dogs

Veterinarians diagnose hookworms by obtaining a stool sample and examining the fecal material under a microscope for the presence of eggs or adult worms.


A dog with hookworms can be treated with a variety of pharmaceutical drugs. However, only hookworms in the intestines will be affected by these drugs, not migratory larvae. As a result, the therapy should be repeated as the larvae grow. A veterinarian, for example, may advise treatment every two weeks. The number of treatments required will vary depending on the dog's age and condition.

It takes a while for infected puppies to shed eggs, so routine deworming of puppies is recommended, even if no signs of hookworms are yet visible.

If you have a pregnant dog, consult your vet for a deworming protocol for both the mother and pups.

Prognosis for Dogs with Hookworms

Adult dogs that are treated for hookworms usually recover in a couple of months. Even with rigorous treatment and supportive care, puppies with severe infestations are more vulnerable to blood loss and anemia, and some puppies may die.

Preventing Hookworms in Dogs

Once de-wormed, many of the monthly medications designed for heartworm and other parasite control contain medication that will prevent hookworm infections on an ongoing basis.

If your dog isn't taking one of these preventatives, your veterinarian will prescribe fecal testing and/or a deworming regimen to keep hookworms at bay. Infection with worms may be avoided by picking up pet feces and keeping pets from eating rodents.

Are Hookworms Contagious to Humans?

Hookworm larvae may infect humans as well as dogs. When people's skin comes into touch with polluted dirt or sand, they become sick. They can potentially accidentally consume eggs if they touch a dog whose fur contains these small particles and then touch their lips.

The larvae usually don't develop into adult hookworms in people. However, the larvae migrating through the skin can cause irritation and inflammation, though most cases are not serious.

To avoid these human health risks, proper hookworm treatment and prevention, as well as appropriate cleanliness, are essential. The same precautions that keep hookworms from spreading from dog to dog, such as proper waste disposal and deworming, can also keep humans from being sick.

If you suspect your pet is sick, call your vet immediately. For health-related questions, always consult your veterinarian, as they have examined your pet, know the pet's health history, and can make the best recommendations for your pet.


"Hookworms In Small Animals. Merck Veterinary Manual." ;