Which of the following intestinal parasites of cats and dogs can affect humans?

A. Toxocara canis ( a roundworm)

B. Ancylostoma caninum (dog hookworm)

C. Echinococcus granulosus (hydatid tapeworm)

D. All of the above


Read on to see if you are right.........

Several types of intestinal worms can affect cats and dogs. 

     These include roundworms, hookworms and tapeworms.




Roundworm and Hookworms have similar lifecycles.  The adult worms live in the intestines.  They lay eggs which hatch in the environment.  The larvae that emerge from these eggs can then infect cats and dogs, or other species including humans.


 Some species of intestinal worms will travel through the body and can be spread to puppies and kittens in the uterus, or through milk in early life.

Figure 4:Toxacara canis lifecycle


 Large numbers of round worms can accumulating in the intestines, and potentially cause an obstruction. Round worms are a common cause of diarrhoea in young puppies. Hookworms suck blood from the intestinal walls. Some of this blood leaks into the intestines and large infections can lead to severe anaemia






Figure  5 :Ancylostoma caninum (dog hookworm) lifecycle.



Tapeworm lifecycle is a bit different.  The tapeworm requires and intermediate host.  This is commonly animals such as fleas, livestock, rodents, rabbits, other small mammals and humans.

The most common species of tapeworm within Melbourne is the Diplydidium caninum (common dog tapeworm). The intermediate host in this worms lifecycle is the flea. The larval flea eats the infective tapeworm segments. The flea goes through its lifecycle, and once fully grown infests a dog or cat. When these fleas are eaten by the dog or cat, then tapeworm hatches and can finish its development.

Dogs and cats that spend time on farms are at a higher risk of becoming infected with Echinococcus granulosus (hydatid tapeworms). The lifecycle for these tapeworm is similar in that there is an intermediate host. For hydatid tapeworms the intermediate host may be rats and mice, rabbits, livestock such as cattle and sheep, or even people. The health implications for humans that become infected with hydatid tapeworms are much more serious than for dogs and cats. All dogs and cats that spend time on farms should be treated for tapeworm every 6 weeks to prevent human infection. For more information on hydatid tapeworm risk in humans in Australia see this press release from the Australian Veterinary Association http://www.ava.com.au/13261

Health Effects on Dogs and Cats

Large numbers of adult worms can damage the intestinal wall and cause diarrhoea.  Depending on the species, these adult worms either feed on the intestines, or the food within the intestines.

With age dogs and cats develop some immunity to round and hookworms. Puppies and kittens have no immunity to these parasites, so it is particularly important to ensure they are wormed more frequently.

Large numbers of tapeworms are required to cause significant disease in cats and dogs, and the proglottid segments can often be seen in the pet’s faeces. Animals on farms, or infected with fleas have higher risks.

Health Effects on Humans

Larval stages of hookworms can cause skin lesions in people.  The larvae live in sand and on grass. A common location for these rashes to occur is on the bottom of feet as a result of walking outside in bear feet. Wearing shoes and washing hands after playing with sand can reduce human infection. It is recommended to keep children’s sand pits covered when not in use to prevent animals defecating in the sand and leaving behind these worms.

Roundworms can cause infections in people. In humans these parasites do not complete the lifecycle to become adult worms.  Instead the larva can cause a localised infection, or may migrate through the body, to lodge in a random location. Laraval roundworms can cause infections in eyes in humans. Again, regular (daily) removal of faeces from the yard will reduce spread of these paraistes.

Tapeworm can be more serious in humans.  Humans act as an intermediate host, and these tapeworm for cysts within the body. These cysts can occur in liver, lungs or brain. This disease is known as Echinococcus.

Removal of faeces daily and regular worming of your pet should eliminate risk of infection to people.


Cleaning up the faeces in the yard on a daily basis will remove worm eggs before they hatch and become infective.

Regular intestinal worming will kill adult worms within the cat or dog.  This should be continued regularly, as your pet may become re-infected by eating things at the park or on walks.

Worming in puppies and kittens should start at an early age, and should be more regular than for adults.  Worming should be done at 2, 4, 6, 8, 10 and 12 weeks of age, then at 4, 5, and 6 months of age.  After this adult worming regimes can start.

Avoid allowing your pet to eat dead animals, or fresh offal. These are common sources for hydatid tapeworm.

For most adult pets we recommend intestinal worming every three months.  However, if your pet travels to a farm, especially one with livestock present, we recommend worming for tapeworm every 6 weeks.




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