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ROUNDWORM INFECTION - (See also Tapeworm)
What
are roundworms?
How did my dog get roundworms?
What kinds of problems do roundworms
cause for my dog?
How is roundworm infection diagnosed?
How are roundworms treated?
Are canine roundworms infectious
to people?
What
can be done to control roundworm infection in dogs and to
prevent human infection?
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 faeces and can be detected by microscopic examination.
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 faeces
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 mobilised by changes in the
bitch's hormonal status as a result of pregnancy and migrate
across the placenta into the foetal 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 puppies.
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 faeces, and the life cycle of the parasite is completed.
Obviously, roundworm eggs passed in one dog's faeces are
infectious to other dogs. Interestingly, a large number of
other animal species have been found to harbour roundworms
and represent potential sources of infection for dogs. These
include cockroaches, earthworms, chickens, and rodents.
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 pot-bellied appearance
to puppies and weakness in adults. Decreased appetite, vomiting
or diarrhoea 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 faeces. They pass only a moderate number of eggs,
so examination of more than one faeces sample may be necessary
to find them. Occasionally, the mature worms can be found
in the dog's faeces 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 anaesthetise 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 faeces. 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 faeces 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 infection?
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 for dogs.
5. Prompt disposal of all dog faeces 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.
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