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Gastrointestinal Parasites of Cats
Gastrointestinal parasitism is a common problem in cats, with
prevalence rates as high as 45 percent. The parasites can be wormlike
(e.g., stomach worms, roundworms, hookworms, tapeworms) or one-celled
(e.g., Isospora, Giardia, Toxoplasma) organisms. The signs associated
with parasite infections are fairly nonspecific, such as a dull
haircoat, coughing, vomiting, diarrhea, mucoid or bloody feces,
loss of appetite, pale mucous membranes, or a pot-bellied appearance.
The vomiting, diarrhea, anemia, and dehydration caused by intestinal
parasites will weaken a cat, making it more susceptible to viral
and bacterial infections and diseases; thus robbing your cat of
good health. Furthermore, some parasites have the potential of
infecting humans.
Wormlike Parasites
ROUNDWORMS
Roundworms (Toxascaris leonina and Toxocara cati) are the most
common intestinal parasite of cats, with an estimated prevalence
of 25% to 75%, and often higher in kittens. The adult roundworms
are 3 to 5 inches long, cream-colored, and live in the cat's intestine.
The adult female worm produces fertile eggs that are passed in
the infected cat's feces. The eggs require several days to several
weeks to develop into the infective larva stage.
Cats become infected with Toxocara cati by ingesting eggs or
by eating rodents (transport hosts) that have larvae in their
tissues. Kittens can become infected by larvae that are passed
through an infected queen's milk. In those cases, it is possible
for kittens to become infected soon after birth. Cats become infected
with Toxascaris leonina in a manner similar to Toxocara cati,
but unlike Toxocara, the parasite is not transmitted through the
milk.
Roundworm infections can potentially become life-threatening
if the numbers are so great that intestinal blockage occurs. Usually,
roundworm infections are relatively benign when compared to other
intestinal parasites. However, infected kittens are in serious
danger if left untreated. Diagnosis is confirmed by finding parasite
eggs in the stool during microscopic examination. Many medications
are effective, but reducing exposure to the feces of an infected
cats and prohibiting hunting are the best means of prevention.
Treatment of queens prior to breeding reduces the likelihood that
the parasite will infect kittens.
Visceral larval migrans and ocular larval migrans are diseases
caused by the migration of Toxocara larvae through the tissue
of people, particularly children. Although these diseases are
rare, they can be quite serious, especially when they occur in
young children. They can be easily avoided by preventing ingestion
of Toxocara eggs in contaminated soil or on the
hands.
HOOKWORMS
Hookworms (Ancylostoma and Uncinaria) are less than 1/2 inch
long, slender, thread-like worms that as adults live in the cat's
intestine. Because of their small size, they usually are not visible
in the feces of infected cats. Hookworms are long-lived and are
capable of living as long as the cat. Less common than roundworm
infections, the prevalence of hookworm infections in North America
is estimated to be between 10% and 60%.
Adult cats usually become infected by larvae that penetrate
their skin or that are ingested. Once the larvae gain entrance
into the host, they migrate to the lungs and then to the intestines
to develop into adult worms. It is uncertain whether cats can
become infected by eating rodents containing larvae in their tissues,
or ingesting queen's milk that contain larvae.
Severe parasitism can cause anemia due to blood loss from the
intestines where the worms attach themselves. The cat's feces
will appear black and tarry due to blood in the feces. If too
much blood is lost, the cat can become anemic and may die if left
untreated. Fortunately, like roundworms, these worms are easily
diagnosed and treated. Good sanitation and daily cleaning of the
litter box are keys to controlling hookworm infections.
Hookworm larvae can penetrate human skin. As they migrate under
the skin, they cause a dermatitis called cutaneous larval migrans.
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TAPEWORMS
Tapeworms (cestodes) have long flattened bodies that resemble
a tape or ribbon. The body is comprised of a small head connected
to a series of segments that are filled with eggs. The adult tapeworm
lives in the small intestine with its head embedded in the mucosa.
As the segments farthest from the head become fully mature, they
break off and are passed in the feces. These segments can be observed
near the cat's tail and rectum, or in the feces. The segments
are about one-quarter inch long, flat, and resemble grains of
rice when fresh or sesame seeds when dry. When still alive they
will usually move by increasing and decreasing in length. Microscopic
examination of fecal samples may not always reveal the presence
of tapeworms, because eggs are not passed singly, but as a group
in the segments. Although the discovery of tapeworm segments can
be quite alarming to cat owners, tapeworm infections only rarely
cause significant disease in cats.
Cats usually become infected with tapeworms by ingesting infected
fleas while grooming or by eating infected rodents. Fleas and
rodents become infected by eating the tapeworm eggs that are in
the environment. Modern medications are highly successful in treating
tapeworm infections, but reinfection is common. Controlling the
flea and rodent populations will reduce the risk of tapeworm infection
in cats.
Some tapeworm species that infect cats can cause disease in
humans if the eggs are accidentally ingested; but good hygiene
virtually eliminates any risk of human infection.
WHIPWORMS
Whipworms are an uncommon parasite of cats in the United States.
Adult whipworms reside in the large intestine of infected cats
but do not cause serious disease.
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STOMACH WORMS
Ollanulus tricuspis and Physaloptera species are worms that
can inhabit the feline stomach. Ollanulus infections occur only
sporadically in the United States and are more common in free-roaming
cats and those housed in multiple-cat facilities. Cats become
infected by ingesting the parasite-laden vomitus of another cat.
Chronic vomiting and loss of appetite, along with weight loss
and malnutrition may be seen, although some infected cats show
no signs of disease. Diagnosis of Ollanulus infection can be difficult,
and depends upon detecting parasite larvae in the vomitus. The
most effective treatment is not known; avoiding exposure to another
cat's vomitus is the most effective means of controlling infection.
Physaloptera infections are even more rare than Ollanulus infections.
Adult female worms attached to the stomach lining pass eggs that
are subsequently ingested by an appropriate intermediate host,
usually a species of cockroach or cricket. After further development
within the intermediate host, the parasite is capable of causing
infection when a cat ingests the insect or another animal (a transport
host), such as a mouse, that has eaten an infected insect. Cats
infected with Physaloptera may experience vomiting and loss of
appetite. Diagnosis relies upon microscopic detection of parasite
eggs in the stool, or seeing the parasite in the vomitus. Effective
treatment exists, and infection can be prevented by limiting exposure
to intermediate and transport hosts.
Neither Ollanulus nor Physaloptera are capable of causing disease
in humans.
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Protozoan Parasites
ISOSPORA
Isospora sp. (coccidia) are microscopic one-celled organisms
causing the disease coccidiosis. Virtually all cats become infected
with Isospora felis during their life. Cats become infected with
this parasite by eating the cyst (thick-walled, egg-like stage)
that has been passed in the feces and has matured in the soil.
The cysts can be infective within six hours after being excreted
in the feces.
Isospora infections usually cause no problems in adult cats,
but evidence suggests that the parasite can cause significant
disease in kittens. In infected kittens, the coccidia destroy
the lining of the intestine and cause diarrhea with often contains
mucous. Serious infections may develop in crowded environments.
Good sanitation and hygiene will help control coccidia, but accurate
diagnosis and effective treatment can only be achieved with your
veterinarian's assistance. Isospora of cats cannot cause disease
in humans.
GIARDIA
Giardia are flagellated protozoa (one-celled organism) that
parasitize the small intestine of cats. The prevalence of feline
giardia infection (giardiasis) is estimated to be less than 5%
but can be much higher in some environments. Cats become infected
by ingesting giardia cysts present in the feces of another infected
animal, usually a littermate or chronic carrier cat. Giardiasis
is more common in multiple-cat households and catteries due to
its mode of transmission. Also, the infection rate is greater
in cats less than one year old.
The cysts are very resistant to freezing. Also chlorination
of municipal water does not destroy the cysts. After ingesting
of Giardia cysts, it takes 5 to 16 days before the cat will show
signs of diarrhea. Acute or chronic, and continuous or intermittent
diarrhea is the most common sign of infection, although the majority
of Giardia-infected cats are free of disease. They do, however,
remain a source of infection to other cats. The cat probably requires
several exposures to the organism before infection actually occurs.
Diagnosis of giardiasis depends upon microscopic identification
of cysts in the stool. For accurate diagnosis, several fecal samples
may need to be evaluated since cysts are not continuously shed
in the stool. Several effective medications are available, but
resistance is common. Elimination of Giardia infections from households
of cats may be difficult and depends on proper treatment and sanitation.
It is uncertain whether species of Giardia that infect cats
are contagious to humans or vice versa. Careful hygiene will eliminate
the risk of accidental ingestion of cysts.
TOXOPLASMA
Cats are the definitive host for the Toxoplasma organism. Infection
with this protozoan parasite is fairly common, but actual disease
caused by this parasite is relatively rare in cats. Cats can become
infected by Toxoplasma by eating any of the three infective stages
of the parasites. The most common route of infection is probably
by ingestion of tissue cysts in infected prey or in other raw
meat. Toxoplasma multiply in the small intestines and in approximately
two to three weeks the oocysts are excreted in the infected cat's
feces. (For more detailed information on this parasite, see
Toxoplasmosis.)
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Treatment
Treatment may require administering one or more dosages of
the medication prescribed by your veterinarian. Whenever using
medications, be sure to carefully follow the directions provided
by your veterinarian.
Parasite reinfections are very common, but can be prevented.
Parasite control begins with good sanitation procedures. This
includes daily removal of feces; washing the litter box with a
disinfectant (e.g., diluted household bleach) on a regular basis;
avoiding overcrowded conditions; avoiding diets with raw meats;
and controlling intermediate hosts (fleas, ticks, and rodents).
Good parasite control is the key to a healthier cat.
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Prepared by the Cornell Feline Health Center,
Cornell University, College of Veterinary Medicine, Ithaca, New
York 14853-6401. The ultimate purpose of the Feline Health Center is to improve the health of cats by developing methods to prevent or cure feline
diseases and by providing continuing education to veterinarians
and cat owners. Much of that work is made possible by the financial
support of friends. ©1981, 1984, 1988, 1996 by Cornell University.
All rights reserved. Cornell University is an equal opportunity,
affirmative action educator and employer.
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