What are roundworms?
As their name implies, these are worms which have round bodies. On average,
they are about 7-12 cm (3-5 inches) long. They live in the dog's intestines
and consume partially digested food. Unlike hookworms, they do not attach to
the intestinal wall; they move freely in their food, the contents of the small
intestine. Roundworms, sometimes called ascarids, pass moderate numbers of microscopic
eggs which are passed in the dog's feces and can be detected by microscopic
How did my dog get roundworms?
Bitches that have had roundworms at any time in the past can transmit them
to their puppies before birth. This is true even if the bitch is not passing
roundworm eggs in the feces because roundworm larvae (immature worms) encyst
in the mother's muscle tissue and are not detected by our tests for adult worms.
These encysted larvae are mobilized by changes in the bitch's hormonal status
as a result of pregnancy and migrate across the placenta into the fetal tissues.
They ultimately mature in the puppy's bowel. Another major source of roundworm
infection for puppies is the mother's milk. Roundworm larvae may be present
in the mother's mammary glands and milk throughout the period of nursing the
Both puppies and adult dogs may become infected by swallowing roundworm eggs
which contain infective larvae. The larvae hatch out in the dog's stomach and
small intestine and migrate through the muscle, liver, and lungs. After several
weeks, the larvae make their way back to the intestine to mature. When these
worms begin to reproduce, new eggs will pass in the dog's feces, and the life
cycle of the parasite is completed. Obviously, roundworm eggs passed in one
dog's feces are infectious to other dogs. Interestingly, a large number of other
animal species have been found to harbor roundworms and represent potential
sources of infection for dogs. These include cockroaches, earthworms, chickens,
What kinds of problems do roundworms cause for my dog?
They are not highly pathogenic (harmful) to adult dogs, but large numbers
can cause weight loss and a potbellied appearance to puppies and weakness in
adults. Decreased appetite, vomiting or diarrhea will be observed on occasion.
Puppies will sometimes die with serious roundworm infections often due to obstruction
of the bowel due to the mass of roundworms.
How is roundworm infection diagnosed?
Roundworms are diagnosed by a microscopic examination of the dog's feces They
pass only a moderate number of eggs, so examination of more than one feces sample
may be necessary to find them. Occasionally, the mature worms can be found in
the dog's feces or vomit sample.
How are roundworms treated?
Treatment is not complicated. Several very safe and effective drugs are available
to kill roundworms in the intestine. Some of these drugs temporarily anaesthetize
the worms so that they pass out of the dog with a normal bowel movement. The
live or sometimes dead worms are found in the feces Because of their size, they
are easily seen. At least two or three treatments are needed; they are typically
performed at 2-4 week intervals. None of these treatments will kill the immature
forms of the worm or the migrating larvae.
The eggs are highly resistant to most commonly used disinfectants and to even
harsh environmental conditions. Therefore, removal of the dog's feces is the
most effective means of preventing reinfection. A 1% solution of household bleach
can be used to remove the sticky outer coating of the eggs, making it easier
to rinse them away. This does not, however, kill the eggs. Remember the obvious
limitations about where bleach may be safely applied.
Are canine roundworms infectious to people?
Yes. The roundworms of both dogs and cats can pose a health risk for humans.
Children in particular are at risk should they become infected. A variety of
organs may be affected as the larvae migrate through the body but the main danger
is that the larvae migrate to the eye where they can cause blindness. In suitable
environments, the eggs may remain infective to humans (and to dogs) for years.
What can be done to control roundworm infection in dogs and to prevent human
1. Pregnant bitches should be dewormed in late pregnancy (after the 6th week
when the encysted larva will be migrating into the bowel, both of the bitch
and the unborn puppies. This will help to reduce potential contamination of
the environment for newborn puppies.
2. All new puppies should be treated by 2-3 weeks of age. To effectively
break the roundworm life cycle, puppies should be dewormed on the schedule recommended
by your veterinary surgeon.
3. Prompt deworming should be given when any parasites are detected; periodic
deworming may be appropriate for dogs at high risk for reinfection. Adult dogs
remain susceptible to reinfection with roundworms throughout their lives.
4. Dogs with predatory habits should be dewormed several times a year. Rodent
control is desirable since rodents may serve as a source of roundworm infection
5. Prompt disposal of all dog feces is important, especially in gardens,
playgrounds, and public parks.
6. Dogs should be discouraged from toiletting in areas normally used by children.
7. Strict hygiene is especially important for children. Do not allow children
to play in potentially contaminated environments.
to Canine Information Index