Hookworm Infection in Cats

By Malcolm Weir, DVM, MSc, MPH; Ernest Ward, DVM; Updated by Amy Panning, DVM

White cat sitting in front of a sandbox

What are hookworms?

Hookworms are intestinal parasites of the cat and dog. Their name is derived from the hook-like mouthparts they use to anchor themselves to the lining of the intestinal wall. They are only about ¼" to ¾ " (roughly 1-1.9 cm) long and so small in diameter that they are barely visible to the naked eye.

Hookworms feed on the tissue fluids and blood of their host. The most common hookworms found in cats are Ancylostoma tubaeforme and Ancylostoma braziliense. Occasionally, cats will also become infected with the dog hookworm, Ancylostoma caninum. Cats can rarely become infected by another dog hookworm, called Uncinaria stenocephala.

In general, cats tend to harbor relatively few hookworms when compared to the large numbers found in dogs. Also, the feline hookworms tend to be less aggressive bloodsuckers than the canine species.

Hookworms are more common in warm, moist environments. Conditions of overcrowding and poor sanitation contribute to infection.

How do cats get hookworms?

Female hookworms pass hundreds of microscopic eggs in the cat's stool. Larvae will hatch from the eggs and stay alive in the soil for weeks to months. When a cat inadvertently swallows larvae, often by grooming its feet, a hookworm infection will become established. Most larvae that are ingested will move to the intestinal tract to complete their life cycle.

"When a cat inadvertently swallows larvae, often by grooming its feet, a hookworm infection will become established."

A few larvae may make their way into the cat’s trachea (windpipe) and are then coughed up and swallowed. The larvae may also burrow through the cat's skin and migrate to the lungs and trachea. The cat will then cough up and swallow the larvae which then migrate to the intestinal tract, where they may mature and complete their lifecycle.

It takes approximately two to three weeks for an infective female larva to mature and produce eggs. Cats can also become infected if they eat other larval hosts such as cockroaches.

In dogs, prenatal infection (infection prior to birth) may be a significant problem. Puppies may become infected from placental blood from their infected mother. Fortunately, this does not occur in kittens. They also cannot be infected through the infected mother’s milk.

What are the clinical signs of a feline hookworm infection?

Evidence of hookworm infection includes anemia (low numbers of circulating red blood cells) the presence of digested blood in the stool (a black ‘tarry’ appearance to the stool), a poor hair coat, and weight loss. Feline hookworms tend to ‘graze’ along the lining of the small intestine and are considered tissue feeders. When they do suck blood, an anti-coagulant substance is injected at the feeding site which prevents the blood from clotting. Therefore, the cat can suffer blood loss from the hookworms feeding, as well as continued bleeding into the bowel from the hookworms' attachment sites. Anemia due to blood loss is a more significant problem in kittens than in adult cats.

"...the cat can suffer blood loss from the hookworms feeding, as well as continued bleeding into the bowel from the hookworms' attachment sites."

Skin irritation and itching, especially of the paws, can be signs of a heavily infested environment since the larvae burrow into and along the skin.

How is hookworm infection diagnosed?

Hookworm infection is diagnosed by a technique called fecal flotation. A small amount of the cat's stool is mixed into a special solution, causing the hookworm eggs to float to the top and adhere to a glass slide that has been placed on the top of the solution. The eggs are easily identified under a microscope because of their unique appearance. Since hundreds of eggs are produced daily, hookworm infection is usually easy to diagnose. The number of eggs does not necessarily correlate with the number of worms present. In fact, the number of eggs passed can be greater with light infections of smaller numbers of hookworms. Due to the small size of the adult hookworms, they are rarely spotted directly in or on the stool.

How is feline hookworm infection treated?

Fortunately, treatment is safe, simple, and relatively inexpensive. After administration of the deworming medication called an anthelmintic, the adult hookworms are killed. However, most anthelmintics do not kill the larval stages. Therefore, at least two treatments are needed, given two to three weeks apart, to kill adults that matured after the previous treatment. Ideally, kittens are treated for worms during their kitten vaccination series.

"Fortunately, treatment is safe, simple, and relatively inexpensive."

Will my cat recover?

With appropriate diagnosis and treatment, the prognosis is good for full recovery from hookworm infection. In rare cases, kittens or debilitated cats might require a blood transfusion because of severe anemia. These patients have a poorer prognosis and extensive treatments are usually necessary.

Can a hookworm infection be prevented?

Prevention of hookworm infection should include the following measures:

• All newborn kittens should be treated with a veterinary-approved anthelmintic by two to three weeks of age. To break the life cycle of the most common intestinal parasites effectively, your veterinarian will recommend a schedule that is appropriate for your kitten.

• Prompt treatment for worms should be given when any parasites are detected; periodic routine deworming may be appropriate for cats at risk for re-infection.

• Use of a monthly heartworm preventive that also prevents hookworm infection is highly recommended.

• Appropriate disposal of cat feces, especially away from yards and playgrounds, is important.

• Strict hygiene is especially important for children. Do not allow children to play in potentially contaminated environments. Be mindful of the risk posed by public parks and sandboxes. Sandboxes that have fitted covers are popular and help to prevent infection of children with intestinal parasites.

• Control of rodents is important since they may play a role in the transmission of hookworms to cats.

• Stools should be removed from litter boxes daily. Always wash your hands after handling fecal material.

Can hookworms be transmitted to humans?

Feline hookworms do not infect humans internally. However, the tiny larvae can burrow into human skin, causing a disease called cutaneous larval migrans. Also known as ‘ground itch’, this skin infection does not lead to the maturation of the larvae. Because contact of human skin with moist, larvae-infected soil is required, infection rarely occurs when good hygiene is practiced.

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