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Common Worms in Dogs and Cats

Did you know that most cats and dogs will contract worms at some stage in their life? These problematic parasites are extremely widespread, affecting dogs and cats of all ages. By being aware of the types, symptoms, and treatment of these worms, you can help protect your pet from serious illnesses.

When we talk about worms, we usually mean these parasites that inhabit the intestines, but pets can pick up worms that affect other parts of the body such as heartworms and lungworms.


Scientific names: Ancylostoma, Uncinaria

These small intestinal parasites (usually ½-1 inch) affect both dogs and cats. Hookworms are named for the hooks they have in their mouths, which they use to attach themselves to the lining of the intestine. Here they feed on the host’s blood, causing intestinal blood loss, anemia, and inflammation of the intestine. This blood loss can be of particular concern for puppies and kittens, who may require a blood transfusion. When the worm reproduces, the eggs pass through the digestive tract and are ejected via the animal’s feces.

How hookworms are transmitted

Hookworms are easily transmitted from another host or from the environment:

  • Orally
  • Through the skin
  • From mother to young in the womb
  • To young through the mother’s milk

Worms and their larvae can live outside an animal host for several months, surviving in feces, dirt, and water. It is easy for a pet to pick up hookworm simply by sniffing feces or grooming their feet after stepping in contaminated soil. Worms or larvae in soil may attach them to an animal’s skin or fur when they lie down and later burrow through the skin to the intestine where they feed and reproduce.

Symptoms of hookworm

As hookworms feed on the intestinal walls, they inject an anticoagulant substance, causing continued bleeding. This blood loss may result in symptoms such as anemia and signs of blood in the feces. Other symptoms may include weight loss, lethargy, a dull coat and failure to grow.

If the larvae have entered through the skin around the feet, you may notice your pet has irritated, itchy or sore skin between their toes.

Hookworm prevention and treatment

Keeping your pet’s environment clean is key. By making sure you pick up feces in your yard, and when you walk your dog, you will help to prevent the spread of hookworm. Rats and mice can also be hosts for hookworm, so be sure control your rodent population, and prevent your cat from eating them.

However, as your dog or cat may easily come into contact with contaminated soil or water, a dewormer is recommended to ensure your pet is protected.

Adult dogs and cats should be treated monthly with hookworm dewormers, which are usually available as part of broad-spectrum medications that treat a variety of intestinal and external parasites. Some of the major brands include Advantage Multi and Heartgard Plus (dogs only).

Pets should be started on wormers at a young age, as hookworm is often passed to puppies and kittens by the mother. Vets recommend treatment for hookworms at 2, 4, 6, and 8 weeks of age, and that the mother is treated at the same time to avoid reinfection.

These medications are used to both prevent hookworm developing and to treat dogs and cats that are infected with hookworm. Puppies and kittens may also need blood transfusions if they have been severely affected by the blood loss.


Scientific name: Toxocara, Toxascaris

Roundworms are some of the most common intestinal parasites found in dogs and cats. The worms themselves are usually white or brown and several inches long, making them easily visible to the human eye when excreted in your pet’s feces or vomit. Roundworms live inside the digestive tract of your pet, not attaching to the walls but living freely within the intestines. Here they feed of undigested food, which sometimes leads to malnourishment- especially in young animals.

How roundworms are transmitted

The most common ways that roundworm is spread is by:

  • Contact with contaminated feces
  • Eating small animals infected with roundworm
  • From mother to young through the placenta
  • To young through the mother’s milk

As roundworms are so widespread and so easily transmitted, nearly all cats or dogs will become infected at some stage in their life. In fact, many animals are born with roundworms or acquire them through their mother’s milk soon after birth. Adult animals can get roundworm by eating another animal that has been infected such as rodents, birds or cockroaches. Roundworm is also transmitted by contact with contaminated feces – your pet doesn’t even have to eat it, just sniffing it can be enough.

Symptoms of roundworm

The effects of roundworm are not necessarily dangerous in adult animals, however, if left to develop into a major infection, your pet may experience weight loss, vomiting, belly pain, and a dull coat.

In puppies and kittens, however, roundworms are more problematic. As the roundworms feed on the partially digested food in the intestines, your pet will become malnourished and fail to grow. In young animals, the symptoms of roundworms may present as vomiting, recurring diarrhea, a potbellied appearance, and stunted growth.

Roundworm prevention and treatment

There are so many ways that your pet can come in contact with roundworms, but there are a number of steps you can take to help prevent the spread of these parasites. Keep your animal’s living area clean by picking up feces in the yard and cleaning your cat’s litter box regularly. Control the population of pests such as cockroaches and mice, and keep your pet in at night to prevent them from eating wild animals.

As roundworms are so common in young animals, puppies and kittens should be treated with a dewormerevery 2-3 weeks from as young as 2 weeks, though it is important to check that the dewormer you use is suitable for young animals. Adult pets should be treated for roundworm at least every 3 months, but ideally they should have a monthly broad-spectrum worming medication such as Sentinel Spectrum (dogs) or Revolution (cats). Your vet may also advise a fecal examination every 6-12 months.


Scientific names: Taenia, Dipylidium Caninum, Echinococcus, Mesocestoides

What we know as tapeworm can actually be one of a number of intestinal parasites, but the most common is Dipylidium Caninum – also known as ‘dog tapeworm’ though it affects both dogs and cats. Tapeworms are long and flat with a body made up of segments, which break off as the worm grows. These segments are often visible in an animal’s stool and are often the first sign the owner recognizes.

How tapeworms are transmitted
Unlike other intestinal worms, tapeworms are not contracted through the environment or from another dog orcat. Tapeworms require an intermediate host to transfer to your pet, so they will only get them by:

  • Ingesting infected fleas
  • Ingesting infected rodents

The lifecycle of the tapeworm works as follows: An infected host such as a dog or cat passes segments of worms via their feces. These worm segments lay eggs in the feces, which are then swallowed by fleas or small animals such as mice. Inside the flea, the egg matures into larvae. If you your dog or cat swallows this flea, the larvae will grow into adult worms in their intestines.

Symptoms of tapeworm

Fortunately, tapeworms are not usually harmful to your dog or cat. The signs that may indicate the presence of tapeworm include segments of worm in the feces, or your pet scooting their behind on the floor when these segments cause irritation. If your pet has a serious tapeworm infestation, they may experience weight loss.

Tapeworm prevention and treatment

As tapeworms are most commonly transmitted by fleas, keeping your pet and their environment flea-free is vital. If your pet does develop tapeworms, a one-off dewormer such as Drontal is a safe and effective way to clear the infection.


Scientific name: Trichuris

Named for their tapered, whip-like shape, these parasites are most usually found in dogs, but may also affect cats. Unlike other intestinal worms, they reside in the large intestine, where they attach the mucosal lining.

How whipworms are transmitted

Tapeworm is only contracted orally, with the most common circumstances being:

  • Ingesting infected meat
  • Ingesting contaminated feces or soil
  • Ingesting contaminated water

One of the reasons that whipworms are so prevalent is that tapeworm eggs are so resilient. The eggs can survive unhatched without a host for up to five years, and are resistant to heat and drying out. Once your pet ingests the contaminated water, soil or other matter, the eggs hatch and complete their lifecycle, developing into adult worms in the intestine.

Symptoms of whipworm

If your pet has just a few whipworms, they may not display any symptoms. More advanced infections can cause problems such as inflammation of the bowel, bloody diarrhea, weight loss and dehydration. If left untreated whipworms can be fatal.

As whipworms can be hard to diagnose, especially in the early stages of infection, an annual fecal test is recommended.

Whipworm prevention and treatment

Whipworms have a very high rate of reinfection due to the hardiness of the unhatched eggs. It is recommended that your pet is treated with a regular worming medication that specifically targets whipworm, such as Sentinel Spectrum (dogs) or Advantage Multi.

Keeping your pet’s environment free of potentially contaminated materials will also help to reduce their exposure to the parasite.

Common Worms in Dogs and Cats

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