Hookworms

Laurie Anne Walden, DVM

Hookworms are common in dogs and cats, especially young animals in warm climates. These parasites are also zoonotic: hookworms that infect dogs and cats can also infect people.
 
What are hookworms?
Hookworms are small parasitic worms that live in the intestines of host animals. Different hookworm species have different preferred hosts. Hookworm larvae can also infect other animals—accidental hosts—that they happen to come in contact with. The symptoms of infection depend on whether the infected animal is a preferred host or an accidental host.
 
Adult hookworms in the intestines lay eggs that are passed out of the body through feces. Once in the environment, the eggs hatch into larvae. Larvae enter a new host’s body by penetrating the skin. Preferred hosts can also be infected by swallowing hookworm larvae, such as by eating contaminated dirt. Puppies can be infected through their mother’s milk.
 
In preferred hosts, hookworm larvae migrate to the intestines, where they grow into adult worms that reproduce and lay eggs. In accidental hosts, hookworm larvae cause a local reaction where they have penetrated the skin, but they do not mature and reproduce.
 
Hookworm infection in dogs and cats
The hookworm species that most often infect dogs and cats are Ancylostoma caninum, Uncinaria stenocephala, Ancylostoma tubaeforme, and Ancylostoma braziliense. These worms attach to the lining of the intestines and feed on blood. Infection can cause anemia from blood loss, which can be fatal in young puppies and kittens carrying large numbers of worms.
 
Symptoms of hookworm infection in dogs and cats depend on the number of worms and the age, size, and overall health of the infected animal.

• Animals with mild infections usually have no symptoms at all.
• Young animals with heavy worm burdens can have pale gums, weakness, failure to thrive, weight loss, diarrhea, black stool (from intestinal bleeding), or sudden death.

 
A number of effective, safe medications are available to treat hookworm infections in dogs and cats. Young animals with severe anemia may need blood transfusions.
 
Hookworm infection in people
Humans can be infected by dog and cat hookworms if they come in contact with larvae in the environment—for example, by walking barefoot on sand or soil contaminated with hookworm larvae. The larvae burrow into the skin, causing an itchy skin reaction called cutaneous larva migrans. The larvae live only a few weeks in humans, so the symptoms may resolve on their own (contact your health care provider if you have more questions).
 
Humans are the preferred hosts for 2 hookworm species: Ancylostoma duodenale and Necator americanus. These hookworms are a major source of human disease worldwide and were once common in the southeastern United States.
 
Preventing hookworms
Because dog and cat hookworms cause serious disease in animals and are also a health risk for people, preventing hookworm infections in our pets is important for both animal and human health.
 
The Companion Animal Parasite Council recommends the following for dogs and cats:

• Have fecal samples tested regularly at the veterinary clinic.
• Deworm puppies and kittens multiple times.
• Deworm pregnant and nursing dogs.
• Use monthly parasite preventives. (Many heartworm preventives also control hookworms; check the label or ask your veterinarian.)
• Keep the environment and litter boxes clean.

 
The CDC recommends these steps to prevent zoonotic hookworm infections in people:

• Wear shoes and protect skin from contact with sand or soil, especially when visiting beaches in tropical or subtropical areas.
• Deworm dogs and cats regularly to reduce environmental contamination.
• Remove animal feces from the environment.

 
For more information
Hookworms (PDF from Worms & Germs Blog)
Hookworms – Dog Owners and Cat Owners (Companion Animal Parasite Council)
Zoonotic hookworm FAQs (CDC)
 
Photo by Andrew Pons

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