Introduction to Hookworms

Hookworms are a troublesome and nasty parasite we occasionally see in our patients. There are three species of dog hookworms and three types of cat hookworms, but the most commonly seen types are Ancylostoma caninum in the dog and Ancylostoma tubaeforme in the cat.

Lifecycle and Transmission

Hookworms live in the small intestine and shed eggs in feces and into the environment where they hatch and develop into larvae. Dogs and cats become infected with hookworms by eating the larvae from the environment, through larva penetrating the skin, and through hunting. Pets may also become infected by eating cockroaches that contain larvae. Puppies may acquire infection through nursing from their mother.

Impact on Health

The hookworms feed by attaching to the lining of the small intestine, digesting the tissue, injecting blood-thinners, and then sucking the blood. Small bleeding ulcers form where the worms once fed. Adult worms can live for 2 years in the small intestine! Hookworms get their name from the ends of their bodies, which are bent, giving them a “fishing hook” appearance. The most common species of hookworm have 3 pairs of teeth in their mouth. The worms themselves are fairly small and range in size from 10 to 20 mm.

Symptoms in Pets

Hookworms can actually cause a nursing puppy to bleed to death if the mom is heavily infected and transmits the worms through feeding the puppy. Puppies may have pale gums, inability to gain weight, poor hair coat, and dark tarry diarrhea. Mature dogs may show few signs if they have a low number of worms, but some adult dogs that have a larger number may show anemia, poor appetite, weakness, and the tarry diarrhea. Hookworms in kittens cause similar symptoms. Respiratory disease and pneumonia may occur in puppies and kittens when larvae migrate through the lungs. Sometimes a rash may be seen on the paws caused by penetration of the larvae.

Diagnosis and Treatment

Diagnosis of hookworms can be made by fecal analysis (fecal testing). Hookworms pass many thin shelled eggs that are passed in the feces. Sometimes the adult hookworms can cause damage by feeding before the eggs are even passed in their feces, so they may have a negative fecal test.

There are many products available from your vet that can treat hookworms. Puppies, kittens and their dams should be treated when their young are 2,4,6,8 weeks of age, and then monthly. Preventing hunting and scavenging by keeping cats indoors and dogs confined to a leash or fenced yard can help reduce the chance of infection. Prompt removal of feces from the litterbox or yard can help prevent the eggs from hatching.

Hookworms and Human Health

Hookworms can infect people as well. The larvae can penetrate the skin, causing an itchy rash. It is possible for the larvae to travel and penetrate into the intestines of people and cause severe abdominal pain, although the worms don’t mature to adults in people. To help prevent infection in people, children’s sandboxes should be covered when not in use, people should wear gloves when gardening, and early and regular deworming of companion animals is essential. For more information on hookworms, and many other parasites, check out the Companion Animal Parasite Council’s website!

Written by Dr. Celeste Forgeron, DVM