Hookworms are a relatively common intestinal parasite affecting dogs, like tapeworms, roundworms, and whipworms. They have hook-like mouth parts that clamp onto the intestinal wall, where they release an anticoagulant and feed on their host’s blood. Hence the name “hookworm.” Hookworm infection is known as ancylostomiasis.
Though these intestinal parasites are more common and more dangerous in puppies, they can certainly infect and affect your service dog. Because they feed on the dog’s blood, and because the anticoagulant can cause continued bleeding even after the hookworms detach from the feeding site, anemia is a concern. In addition to the discomfort and suffering these worms can cause your assistance dog, she may become more unfocused, weak, and lethargic, meaning she might not be up to her important jobs.
How Dogs Contract Hookworms
Puppies often become infected by hookworm larvae from their mother. The larval-stage parasites can pass through the placenta and infest the unborn puppy, and they can also pass through the mother’s milk and infect the puppy post-birth during feeding.
Hookworm eggs are laid in the intestines and passed out of the host through feces. Larvae develop from the eggs and can remain infective in the environment for weeks or months without a host. Dogs may ingest eggs or larvae while sniffing around a contaminated area; sniffing, licking, or eating contaminated feces; or grooming themselves after passing through an area with eggs or larvae.
Unlike the other three common intestinal parasites affecting dogs, hookworms also have the ability to burrow into a host through its skin, making them even easier to contract. A dog can therefore become infected just by walking or lying in a contaminated area.
Symptoms and Complications of Hookworm Infections
Not all dogs present symptoms of a hookworm infection, especially if it isn’t particularly extensive. However, a general unwell appearance and loss of appetite are common. Diarrhea, vomiting, blood in the stool, dark or tarry stool, and weight loss are other possible signs. Larvae sometimes pass into the host’s lungs, which may trigger coughing.
As mentioned above, anemia is a significant symptom and complication of a hookworm infection. The gums and lining of the lips, nostrils, and ears often become pale with anemia, and the dog loses strength and energy. Diarrhea and vomiting also pose a risk of causing dehydration if the dog isn’t drinking enough water.
Diagnosis and Treatment of Hookworms
If your assistance dog has a hookworm infection, large quantities of eggs pass in her stool on a daily basis, making ancylostomiasis easy for your vet to diagnose with a fecal sample. Hookworms are the smallest of the four most common intestinal worms; thin and only about 3 millimeters long when fully grown, they aren’t generally seen by the naked eye.
Treatment is simple and straightforward with anthelmintics, a class of antiparasitic drugs that are highly effective against intestinal worms. Your vet will recommend a particular product and instruct you on dosing and administering a second dose. Because these medications only kill adult hookworms, and not the eggs or immature larvae, a second dose is needed two to four weeks later to kill the worms that mature after the first dose.
Rarely—and usually in puppies when it does happen—severe anemia may require treatment with a blood transfusion.
Preventing Hookworm Infections in Your Assistance Dog
In most cases, vets advise that adult dogs regularly take a heartworm preventative, and most of these also effectively prevent hookworm infections. Ask your vet about this and follow the dosing instructions and de-worming schedule provided for your service dog. Also, make sure your vet performs a fecal exam as part of your dog’s annual or semi-annual checkups.
Immediately pick up, seal up, and dispose of feces when your assistance dog relieves herself, and make sure she doesn’t approach stool left behind by other animals. Remember, hookworm larvae can burrow through the skin—including human skin—so don’t ever touch feces with your bare hands.
Regarding this last point: Larvae can enter humans through their skin (usually causing considerable itching at entry sites), but they don’t mature into adult worms in human hosts or feed in the intestines. However, the larvae can migrate to the eyes or internal organs and do serious damage. It’s not common, but it’s definitely not something anyone wants to risk.