Internal Parasites

Most internal parasites are worms and single-celled organisms that
can exist in the intestines of dogs or cats. The most common worms
are roundworms, hookworms, whipworms and tapeworms. Common
single-cell parasites are coccidia and Giardia.
What are roundworms and how are they spread?
Roundworms are the most common intestinal parasite in dogs and
cats in the world. Animals with roundworms pass the infection to
other animals when the worm eggs develop into larvae and are
present in the animal’s feces (droppings). Your pet can pick up the
infection by eating infected soil, licking contaminated fur or paws,
or by drinking contaminated water.
Infected female dogs may pass the infection to their puppies before
birth or afterwards when they are nursing. Infected female cats
cannot infect their kittens before birth, but can pass on the infection
through their milk when kittens are nursing.
What are the health risks to pets and people?
What are hookworms and how are they spread?
Hookworms are the second most common intestinal parasites
found in dogs, but they are less commonly found in cats. Your pet
can become infected when larvae penetrate the animal’s skin or the
lining of the mouth. An infected female dog can pass the infection
to her puppies through her milk, but this does not occur in cats.
What are the health risks to pets and people?
Hookworms are dangerous parasites because they actually bite into
the intestinal lining of an animal and suck blood. As with roundworms,
puppies and kittens are at high risk of infection and developing severe
disease. Left untreated, hookworm infections can result in potentially
life-threatening blood loss, weakness, and malnutrition.
Like roundworms, hookworm infections are zoonotic, and infections
usually occur by accidentally eating the larvae or by the larvae
entering through the skin. In humans, hookworm infections cause
health problems when the larvae penetrate the skin. The larvae
produce severe itching and tunnel-like, red areas as they move
through the skin and, if accidentally eaten, can cause intestinal
problems.
What are whipworms and how are they spread?
These worms get their name from their whip-like shape. Animals
with whipworms pass the infection along to other animals when
the worm eggs develop into larvae and are passed in their feces
(droppings). Your pet can pick up the infection by eating infected
soil or licking their contaminated fur or paws.
What are the health risks to pets and people?
Like hookworms, whipworms bury their heads in the lining of an
animal’s intestine and suck blood, but they are generally less harmful
and usually do not cause health problems. Occasionally, severe
infections can develop and lead to diarrhea, weight loss, and blood
loss. Whipworm larvae rarely infect humans when they are accidentally
eaten.
What are tapeworms and how are they spread?
Tapeworms got their name because they are thin and flat, like
strips of tape. Unlike the smooth-bodied roundworms, hookworms,
and whipworms, tapeworms’ bodies are actually made up of joined
segments. Dogs and cats become infected with tapeworms when
they eat infected fleas or lice. They can also get certain types of
tapeworms by eating infected rodents.
What are the health risks to pets and people?
Tapeworms live in the small intestine and steal the nutrients from
the food your dog or cat eats. An infection is usually diagnosed
when the eggs sacs are seen under the pet’s tail or on its stool. These
sacs look like flattened grains of rice. While there are several
dewormers available that are effective against tapeworms, keeping
your pet free of fleas is the best preventative. Rarely are tapeworms
a risk to people.
How can I prevent/treat worm infections?
Puppies and kittens are the most prone to roundworm infection.
Because roundworms live in the small intestine, they steal the
nutrients from the food pets eat, which can lead to malnutrition
and intestinal problems. As the larvae move through a pet’s body,
young animals may develop serious respiratory problems such as
pneumonia.
Roundworm infections are zoonotic (pronounced zoe-oh-NOTick)
diseases, meaning that they are animal diseases that can be
transmitted to humans. While direct contact with infected dogs
and cats increases a person’s risk for roundworm infection, most
infections come from accidentally eating the worm larvae or from
larvae that enter through the skin. For example, children are at risk
for infection if they play in areas that may contain infected feces,
(such as dirt piles and sandboxes), where they pick up the larvae
on their hands.
Left untreated, roundworms in people can cause serious health
problems when the larvae enter organs and other tissues, resulting
in lung, brain, or liver damage. If the roundworm larva enters the
eyes, permanent, partial blindness can result.
Healthy pets may not show outward signs of a worm infection.
However, if you notice a change in your pet’s appetite or coat,
diarrhea, or excessive coughing, see your veterinarian. In most cases,
a simple fecal test can detect the presence of worm eggs or adults
and, if present, your veterinarian will recommend a deworming
program. A good way to prevent most worm infections is by using
one of several monthly heartworm preventatives available from
your veterinarian.
Nursing female dogs and cats and their litters are also major sources
for the spread of infective eggs and larvae. If you have a new puppy
or kitten, or a pregnant pet, consult with
your veterinarian about a deworming
program that will reduce your family’s risk
of infection.
Worm infections in humans can be easily
prevented by practicing good hygiene and
sanitation. Children should be discouraged
from eating dirt and should not be allowed
to play in areas that are soiled with pet feces.
Sandboxes should be covered when not
in use. Adults and children should always wash their hands after
handling soil and after contact with pets. Shoes should be worn
when outside to protect feet from larvae present in the environment,
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and raw vegetables should be thoroughly washed because they may
contain parasites from infected soil.
Dog droppings should be immediately picked up from public areas
and from your yard to reduce the chances of contaminating the soil.
Keeping cats indoors is an effective way to limit their risk of exposure
to roundworms.
Other internal parasites
Coccidia
Coccidia (cok-SID-ee-ah) are single-celled parasites and are not
visible to the naked eye. Your pet can become infected by eating
infected soil or licking contaminated paws or fur. Once swallowed,
the parasites damage the lining of the intestine and your pet cannot
absorb nutrients from its food. Bloody, watery diarrhea may result,
and the animal may become dehydrated because it loses more
water in its stool than it can replace by drinking. Young pets are
most often infected because their immune systems may not yet
be strong enough to fight off the parasite. Coccidia can be very
contagious among young puppies and kittens, so households with
multiple pets should be especially careful to practice good hygiene
and sanitation.
A routine fecal test by a veterinarian will detect the presence of
coccidia. Treatment with medications will prevent the parasite
from multiplying and allow time for your pet’s immune system
to kill the parasites.
Giardia
Giardia (gee-AR-dee-ah) is also a single-celled parasite that, if
swallowed, damages the lining of the intestine and reduces the
absorption of nutrients from the food your pet eats. While most
Giardia infections do not cause illness, severe infections can lead
to diarrhea.
Giardia is harder to diagnose than other intestinal parasites, and
several stool samples may have to be tested before it is found. If
necessary, your veterinarian will recommend treatment with
medications to eliminate the infection. Because it is highly contagious
among animals, good hygiene and sanitation are important when
there are multiple pets in the household.
• See your veterinarian if your pet has diarrhea, weight loss,
increased scooting, a dull coat, or if you see worms under its tail,
in its bedding, or on its stool.
• Prompt treatment of internal parasites lessens your pet’s
discomfort, decreases the chances of intestinal damage, and
decreases the chance that your pet will infect humans or other
animals.
• Good hygiene and sanitation reduce the chances that your pet
will infect people or animals. You can help prevent the spread
of infection by always cleaning up your pet’s droppings immediately.
IMPORTANT POINTS ABOUT INTERNAL PARASITES