Round & Hook Worms


There are various pests that can infect your pets, both outside on their skin or inside their intestines and other internal organs. Veterinarians recommend that dogs and cats get dewormed regularly to get rid of these pesky parasites, which they can sometimes carry inside them for some time without showing any signs of infection. Your veterinarian will choose a medication based on many factors including your pets age, the time of the year, and how much contact they have with other animals.

Two common intestinal parasites targeted by many deworming products are roundworms and hookworms, which can infect dogs, cats, and humans.


There are three types of roundworms that can affect your pets. Cats can be infected with Toxocara cati, and dogs can be infected by Toxocara canis. Both cats and dogs can be infected by Tocascaris leonina.

How does a pet become infected?

Adult worms release eggs into the intestines of their host and the eggs are carried out into the environment in feces. Pets can get infected by consuming an infective egg found in soil (from grooming or eating something off the ground). It takes 30 days for an egg to become infective, so fresh feces is not a source of infection. Eggs can survive in the soil for a long time and be infective for months to years.

Why is it bad?

  • Roundworms can cause diarrhea and vomiting. White string-like worms can sometimes be seen in the feces or vomit of an infected animal.
  • Infections can cause your pet to have a pot-bellied and generally poor appearance.
  • Decreases nutrient absorption, which is especially harmful to puppies and kittens.
  • The larval stage of the roundworm can migrate through your pet’s body to their lungs and in severe cases can cause pneumonia.
  • Heavy infections can block your pet’s intestines.
  • Roundworms can also infect people, causing abdominal pains, fever, headaches, coughing, and blindness as the worm larvae migrate through the body. Young children are at risk because they are more likely to play in infected soil and put dirty objects in their mouth.


There are two hookworm species that infect dogs, Ancylostoma caninum and Uncinaria stenocephala, and one that infects cats, Ancylostoma tubaeforme, while Ancylostoma braziliense can infect both dogs and cats.

How does a pet become infected?

  • Eggs from mature worms are released into the intestines and are passed in feces. The eggs hatch in the environment where the larval form infects another animal by getting eaten or by crawling through the skin of their new host. Dogs and cats can also be infected by eating an animal or insect that has hookworm larvae inside it.
  • Larvae are passed to puppies before they are born by migrating through the mother’s body, and also immediately after birth through their mother’s milk or infected stool.

Why is it bad?

  • Hookworms suck blood from inside the intestines, which can cause extensive blood loss and anemia.
  • After the larva infects a host they mature in the intestines or migrate through the body to other locations like the lungs, where they can turn into cysts.
  • Hookworms can infect humans through poorly washed contaminated food or through penetration through bare skin that contacts soil with hookworm larvae. In humans they can cause gastrointestinal discomfort, anemia, and itchiness if they migrate through the skin.

How do you get rid of worms?

  • Ask your veterinarian for the most appropriate deworming product for your pet. Most products work by anesthetizing the worm so it can’t hold on inside your pet’s intestines and can be passed in the feces. Don’t be alarmed if you see some worms after deworming your pet, especially if it’s the first time.
  • It’s possible to look at the feces of your pet under a microscope to see if eggs are present, but fecal exams will only be positive if there are adult worms releasing eggs in the intestines. Many tests will appear negative even if your pet is infected with worms.
  • Puppies and kittens are always assumed to be infected because they can get worms from their mother, so frequent deworming is recommended.
  • Pets that hunt or have access to rodents are especially susceptible to parasite infections.
  • Worms can only be affected by deworming medication when they are in the intestines of your pet, so the larvae that are migrating through the body or hookworm cysts will be missed. That’s why it’s important to deworm a second time a few weeks after the first dose and keep them on a regular deworming schedule.

Written by Alicia Naundorf, RVT