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Roundworms are one of the most common intestinal parasites of the cat. They can be an important cause of illness, even death, in kittens. As their name implies, these are large-bodied round worms, averaging about 3-6 inches (8-15 cm) in length. They do not attach to the wall of the intestine, as some intestinal parasites do. Instead, they are literally "swimming" freely within the intestine.
The scientific name for the feline roundworm is Toxocara cati. Another less common roundworm, Toxascaris leonina, can infect both dogs and cats. Roundworms are sometimes called ascarids and the disease they cause is called ascariasis.
"...large numbers may cause life-threatening problems in kittens and debilitated older cats."
Roundworms are not particularly pathogenic or harmful to adult cats, but large numbers may cause life-threatening problems in kittens and debilitated older cats. In kittens, common clinical signs include a pot-bellied appearance, abdominal discomfort, depressed appetite, vomiting and diarrhea, or poor growth.
In both kittens and adult cats with small numbers of worms, there may be no clinical signs of infection.
Trans-mammary or milk-borne infection is the major route of roundworm transmission in kittens. The immature roundworms called larvae are present in the mother's mammary glands and pass through her milk to the kittens during nursing.
Both kittens and adult cats may become infected by swallowing eggs that contain infective roundworm larvae. These eggs may come from the feces of infected cats or from the tissues of paratenic hosts. In a paratenic host, the roundworm eggs do not mature into adults, but are merely transported. If a cat eats the paratenic host, the roundworm is able to complete its maturation. Common paratenic hosts for roundworms include earthworms, cockroaches, rodents and birds.
The lifecycle of the roundworm is complicated. Once ingested, the larvae hatch out in the cat's gastrointestinal tract and migrate through the muscle, liver, and lungs. After several weeks, the larvae return to the intestine to mature into adults. When the adult worms begin to reproduce, eggs will pass into the cat's stool, thus completing the life cycle of the parasite.
During migration, some roundworm larvae may encyst in a dormant state in the host's body. In female cats, the larvae can come out of dormancy during pregnancy and be passed to the kittens across the placenta or through the milk.
To diagnose roundworm infection, a small amount of the cat's stool is mixed in a special solution that causes the eggs to float to the top of the solution. The sample is covered with a glass slide on which the floating eggs will collect, and the slide is examined under a microscope.
"The distinctive eggs are easily recognized under the microscope."
The distinctive eggs are easily recognized under the microscope. Roundworm eggs are usually plentiful but, in some cases, it may take more than one fecal examination to find them. Occasionally, intact adult roundworms can be found in the cat's stool or vomit.
Fortunately, the treatment for roundworms is safe, simple, and relatively inexpensive. The dead and dying roundworms pass into the stool after administration of the anthelmintic or deworming medication. Since none of these treatments will kill the immature forms of the worm or the migrating larvae, at least two or three treatments are needed; they are typically performed at two to three week intervals. Ideally, kittens are dewormed with each visit for booster vaccinations. If your adult cat goes outdoors, you may wish to administer periodic doses of an anthelmintic.
The prognosis of a roundworm infection is good if appropriate medication is given promptly. However, in some instances, extremely debilitated kittens may die.
Prevention of roundworm infection should include the following measures:
"First deworming should be given at two to three weeks of age."
"Rinse the litterbox thoroughly to remove all bleach since it is toxic to cats."
Roundworms can be a health risk for humans. The most common source of human infection is by ingesting eggs that have come from soil contaminated with cat (or dog) feces.
"In suitable environments, the eggs may remain infective to humans and cats for years."
As many as 10,000 cases of roundworm infection in humans have been reported in one year in the United States. Children are at an increased risk for health problems should they become infected. A variety of organs, including the eyes, may be affected as the larvae migrate through the body. In suitable environments, the eggs may remain infective to humans and cats for years.