Hookworms are small, thin worms about 1⁄4 to 1⁄2 inches (.6 to 1.3 cm) long. They fasten to the wall of the small intestines and draw blood from the host. There are four species of hookworms that afflict the cat. Hookworms are not as common in cats as they are in dogs. They are most prevalent in areas that have high temperature and humidity (for example, in the southern United States), where conditions are favorable for the rapid development and spread of larvae.
A cat acquires the disease by ingesting infected larvae in soil or feces or by direct penetration of the skin (usually the pads of the feet). In rare cases, a cat may acquire the parasite by eating mice that host the larvae. The immature worms migrate through the lungs to the intestines, where they become adults. In about two weeks, the cat begins to pass eggs in her feces. The eggs incubate in the soil. Depending on conditions, larvae can become infective within two to five days after being passed.
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The typical signs of hookworm infestation are diarrhea, anemia, weight loss, and progressive weakness. With a heavy infestation, stools may be bloody, wine-dark or tarry-black, but this is uncommon. A hookworm infestation can be fatal in very young kittens. The diagnosis is made by finding the eggs in the feces.
Newborn kittens do not acquire the infection in utero but might via the milk of the queen. Chronic infestation is a more common problem in adult cats than it is in kittens.
Many cats who recover from the disease become carriers via cysts in the tissue. During periods of stress or some other illness, a new outbreak can occur as the larvae are released.
Treatment: Pyrantel pamoate and selamectin have become the deworming medications of choice because of their safety and effectiveness. Milbemycin and ivermectin are also very effective dewormers but are generally used only in older kittens and adult cats. Two treatments are given two weeks apart. The stool should be checked to determine the effectiveness of treatment.
Kittens with acute signs and symptoms require intensive veterinary management.
Public health considerations: A disease in humans called cutaneous larvae migrans (creeping eruption) is caused by hookworm species. Larvae present in the soil penetrate the skin and travel through the body. It causes lumps, streaks beneath the skin, and itching. The condition is self-limiting.
WebMD Veterinary Reference from "Cat Owner's Home Veterinary Handbook"