Worms and Zoonosis

Can I get worms from my dog or cat?

 Yes.  We can get a lot of different kinds of worms from our pets.  For the purpose of this handout, we will refer to roundworms and tapeworms as they are the most commonly seen ones in animal shelters.

How can I get roundworms?

In order to get roundworms, you need to ingest the roundworm eggs that are shed in your dog or cat’s feces.  This doesn’t means that you need to sit down at the kitchen table with a knife and fork!  It is easier than you would think to ingest a bit of dog or cat poop that might have roundworm eggs in it.  Our pets roll around in poop, either intentionally or not! So even though we don’t normally snuggle up to the back ends of our pups, through grooming we can spread bits of feces to other parts of their bodies.  If we let our pets sleep with us, or let them lick off our spoons or don’t wash our hands it doesn’t seem so farfetched to think that we can easily ingest feces!

What do roundworms do to us if we get them?

Roundworms cause a disease called visceral larva migrans.  After we accidentally ingest the eggs, they hatch in the upper portion of the small intestine.  These little larvae penetrate the gut wall and make their way to the lungs.  Once in the lungs, they enter the bloodstream and are transported to all parts of the body.  When they are in the capillaries, they actively move out into other tissues.  Their favourites are the liver, the brain, spinal cord and the eye.  As they are moving through these different organs, they are causing permanent damage which may lead to lifelong neurological and ocular problems.  They can also cause severe allergic reactions.  In the USA, 10 000 new cases of visceral larva migrans and 700 of ocular larva migrans are diagnosed every year.

How do we get tapeworms?

There are two different ways that we can get tapeworms from our cats or dogs because there are two different types of tapeworms that can commonly infect us.  The first is Dipylidium caninum.  In order for this species of tapeworm to complete its life cycle (to go from egg to adult) a part of its life cycle must be completed within a flea.  We couldn’t get infected by eating the tapeworm eggs directly because that critical stage within the flea wouldn’t happen.  Therefore, in order for us to be infected by this species we must consume a flea that has eaten the tapeworm eggs.  Again, it is not to farfetched to imagine consuming a flea!  Dogs chew on fleas when they get bitten, and also like to lick our hands and faces.  Put two and two together and you’ve got a tapeworm infection!  The other type of tapeworm that we are commonly exposed to by our pets is Echinococcus granulosus.  These tapeworms don’t have that intermediate stage within the flea so we can become infected by ingesting the eggs that come out of the dog when id defecates.  Just like with roundworms, consuming a bit of egg laden dog feces in not too hard to imagine.

What do tapeworms do to us if we get them?

Fortunately, Dipylidium caninum does not cause major medical problems for us.  It doesn’t affect any organs other than digestive tract.  Someone who has picked up the parasite will end up shedding tapeworm segments in the same way that dogs and cats do. With heavy infestations the person may suffer from abdominal pain, mucous-filled and bloody diarrhea and weight loss.  Unfortunately, having an Echinococcus granulosus infection is a different story.  After ingestion of the eggs, they hatch and the larvae migrate most commonly to the liver and lungs through the blood vessels.  Once in the liver and lungs, the larvae form cysts that enlarge over time.  These cysts can cause embolisms, can disturb liver function and the fluid produced by the cysts can cause fatal anaphylactic reactions.

How can we prevent getting worms from our dogs and cats?

The easiest way is to have your pet de-wormed every year. It is not necessary to avoid showing affection for your pet, just try to be conscientious about the type of contact.  Wash your hands before and after handling pets and avoid having dogs lick your face if possible.

Children are at greater risk of getting worms from pets.  They are less likely to wash their hands and more likely to be in contact with animals.  Also, children are more likely to roll around in grassy areas in which animals have gone to the bathroom (i.e. Sand at beaches, playgrounds etc.).