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The Inside Story on Parasites in Cats
By: Eric W. Averill D.V.M
Although cats are susceptible to a variety of internal parasites, only a few
are significant enough to mention.
They are roundworm, hookworm, tapeworm, coccidia, and heartworm.
Roundworm (Toxocara Cati) is quite common in kittens. It is inherited from
the queen even if she has no current infection. That's because of an
encysted form that lies dormant in a cat, coming out only during pregnancy
to affect the kitten.
They are not seen except when vomited, and are best described as the
shape of spaghetti. These buggers do present a health hazard to children
under less than sanitary conditions. That's why veterinarians have begun to
worm kittens 2-3 times even if the fecal examinations are negative. I try for
a combination of worming and fecal examinations that total three for all
Adult cats may occasionally vomit a roundworm, but infestations bad
enough to cause illness are unusual. There is a natural immunity that
develops with a cat's maturity.
Hookworms are not common in cats in the Northeast, but they are
occasionally responsible for anemia and intestinal illness in cats. Most of
medications used to treat the roundworm will also kill hookworms.
Coccidia are protozoan parasites that can cause diarrhea, especially in
young cats. They are usually self-limiting, and often do not cause illness,
should be treated when there are bowel symptoms. Giardia and
Toxoplasmosis are members of this club, but the most common coccidia
are called Isospora.
Then, there is the tapeworm. This worm is made up of a long series of
segments, which drop off the worm one by one and are visible in the stool,
or around the hair of the rear. When they dry out, they appear like grains of
rice. Nothing grosses out cat owners more than wiggley little white
creatures on the rear end of the cat. Although these parasites seldom cause
any illness, it is quite understandable that cat owners are anxious to
These worms are acquired through flea infestation and so can affect indoor
cats that are exposed to fleas. Naturally, the flea problem also has to be
addressed. Hunting rodents can also lead to infestation.
There are good therapies for all these inside interlopers. Fecal examinations
should be done routinely on all cats that go outside, and on cats that stay
but share litterboxes with outdoor cats.
That's why, as with all other intestinal parasites, treatment should be
directed to all cats that share a household or litter box. Fecal examinations
should always accompany the treatment of any intestinal illness.
The only other internal parasite I want to discuss is the heartworm. Cats are
not natural hosts of this parasite, but veterinarians are recognizing that
infestation occurs in cats at a rate estimated at 1/5 that of dogs. Unlike the
dog, heartworms do not prosper in cats. They live only a year or two if they
manage to grow into adults at all. Most die and cause little harm to the cat.
In some cases however, a dead or dying worm can cause the rapid death of
a cat. There is no safe treatment
The risk of this occurrence is not clear for us in New England. Although
there is no precise diagnostic blood test for cats, there is preventative
medication, identical to that given to dogs. I do not presently recommend it
for cats, but I may in the future if a significant risk is demonstrated.