

Intestinal Worms in Dogs



The larva can infect its new host in several ways. One way is to penetrate the host's skin directly through the feet or belly or whatever part of the skin is touching the ground. Another way for the larva to gain entry to the new host is to be present in soil that is licked and swallowed by the host as it cleans itself.

Infection of a very young puppy can occur in two additional ways. Typically an infected mother dog will have encysted larvae all around her body. Throughout the adult dog's life, some larvae will awaken, break out of their cysts, and complete their migration to the GI tract.

Pregnancy hormones unfortunately serve as little wake-up calls to encysted hookworm larvae, only this time the little worms migrate to the unborn puppies and to the mammary gland.

Some members of the litter will be born infected. Others will become infected by drinking the contaminated milk of their own mother. If this is not enough to infect the entire litter, others will become infected from the soil of their own nest, which will quickly become contaminated, with the stool of the infected litter.


Simply killing the worms will not be sufficient to save the life of a severely affected puppy. Like any other blood loss, a transfusion may be needed to keep the puppy alive until it can replace its own lost red blood cells.

Fortnightly worming with an effective product from 2 weeks of age is the best way to prevent hookworm becoming a problem.


Adult roundworms are large enough to be seen in droppings, if they haven’t been digested during the “passage”. They drain protein from the host. For this reason, roundworms are more harmful to young animals, who require much nourishment while they are growing. Roundworms cause diarrhea, vomiting, poor appetite and poor growth. Severe infections can result death from intestinal obstruction.

In dogs, there are four ways by which infection with Roundworm (Toxocara canis) occurs:

  • Consuming infective worm eggs from soil in the environment (generally through normal grooming).
  • Nursing from an infected mother dog.
  • Consuming a prey animal (usually rodent) that is carrying developing worms.
  • During embryonic development when an infected mother dog is pregnant (most puppies are infected this way).

Humans can be infected by roundworms. If a human ingests the roundworm eggs, the roundworm larvae can migrate throughout the body, causing a condition known as Visceral Larval Migrans, a very dangerous condition. Roundworms in humans will occasionally migrate to the eye and destroy the retina, causing permanent blindness. While this is rare, it happens most often in the tropics, where roundworm is a serious problem. Children are more susceptible than adults.


Whipworms occur in dogs, not cats. They live in the large intestine. They usually do not cause major illness (unless the infection is severe), but will still have a negative impact on the dog’s health, and create itchy bottoms! Whipworm eggs have an ability to survive a long time in the soil. Whipworms cannot be transmitted to humans.


Several types of tapeworm effect cats and dogs.

  • The flea tapeworm is the most common tapeworm infecting cats and dogs. Infection occurs when the animals ingest a flea that has eaten tapeworm eggs. The flea tapeworm does not cause serious illness, however, it does ingest protein through the intestinal wall. Flea control is as important in preventing re infestation of flea tapeworm as the worm products used. People can get them but they must be infected the same way dogs and cats are: by swallowing an infected flea!
  • Hydatid tapeworms are VERY DANGEROUS to humans, but are not a worry here in Darwin. They are commonly seen in dogs that eat uncooked offal of sheep, kangaroos, and other animals. For this reason, they are found in southern rural areas, but not generally in suburban Darwin. In humans, they cause cysts in the liver and lungs of infected people.
  • Spirometra tapeworms do occur in Darwin (they are uncommon in many other areas of Australia). They are called ‘zipper’ tapeworms, due to their appearance. Dogs and cats that ingest lizards, snakes and frogs, or drink from water where there have been water beetles, are at risk. We recommend that all dogs and cats in the Top End are treated for this worm, which requires an unusually high dose of tapeworm tablets (given every 3 months from 16 weeks of age).

How often should I worm my dog?

Most dogs need to be wormed more frequently in Darwin than in other areas of Australia. Each time we give a worming medication, it kills any worms that are present, rather than providing protection for a certain amount of time. When there are more worms around, we need to treat more frequently.

We recommend worming puppies fortnightly from 2 weeks of age to 16 weeks of age, and then monthly for life. There are a number of effective products available for intestinal worms. We recommend Cazitel or Drontal (which contain Pyrantel, Febantel and Praziquantel) or a combined product containing milbemycin which also prevents Heartworm +/- fleas (eg. Milbemax, Interceptor, Panoramis). If a monthly combined product such as Panoramis or Interceptor is given, a dose of Cazitel in between doses is needed until 16 weeks of age (to achieve fortnightly worming).

Some of these products will treat the flea tapeworm, but none will treat the Spirometra tapeworm. To treat this a higher dose of tapewormer is given every 3 months, starting at 16 weeks of age.

Most supermarket products are not effective enough in Darwin. 

comments powered by Disqus