Hookworm Infection in Cats

What are hookworms?

Hookworms are intestinal parasites found in cats and dogs. They get their name from the hook-like mouthparts they use to anchor themselves to the lining of the intestinal wall. They are only about ¼" to ¾" (1-1.9 cm) long and so small that it is very difficult to see them with the naked eye.

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 become infected by another dog hookworm, called Uncinaria stenocephala, but it is a rare occurrence.

Despite their small size, hookworms ingest large amounts of blood from the tiny vessels in the intestinal wall, although feline hookworms tend to be less aggressive bloodsuckers than the canine species. In general, cats tend to harbor relatively few hookworms compared to dogs. Hookworms are more common in warm, moist environments. Conditions of overcrowding and poor sanitation contribute to infection.

How do cats get hookworms?

Cats may become infected with hookworms via one or all the following routes:

• Oral ingestion of larvae 
• Oral ingestion of an animal with infective larvae in their tissues (e.g., a cockroach)
• Skin penetration

A cat may become infected when it inadvertently swallows hookworm larvae, often by grooming its feet or sniffing contaminated soil. Cats can also become infected if they eat other larval hosts, such as cockroaches. The larvae may also burrow into the cat’s skin if it walks or lies on contaminated ground.

Most hookworm larvae that a cat swallows move to the intestines, where they mature into adult worms. The larvae that enter through the skin migrate through the body to the lungs. From there, they are coughed up and swallowed, gradually moving to the intestinal tract, where they mature into adults.

In the intestines, female hookworms lay hundreds of microscopic eggs that leave the dog with their feces and contaminate the environment. Larvae hatch from the eggs and can remain infective in the soil for weeks to months. Fortunately for kittens, they cannot be infected through the mother’s milk like puppies can.

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.

"Pale gums and weakness are common signs of anemia."

Feline hookworms tend to “graze” along the lining of the small intestine and are considered tissue feeders. When they do suck blood, they inject an anti-coagulant substance that 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 attachment sites. Pale gums and weakness are common signs of anemia. Anemia due to blood loss is a more significant problem in kittens than in adult cats. In a heavily infested environment, cats may have skin irritation and itching, especially of the paws, caused by larvae burrowing into and along the skin.

How is hookworm infection diagnosed?

Hookworm infection is diagnosed using a technique called fecal flotation. The stool is mixed with a solution that causes the parasite eggs to float to the top and adhere to a glass slide placed on the surface. Hookworm infections are easily detected because they produce many eggs daily and the eggs have a unique appearance. The number of eggs does not necessarily correlate with the number of worms present; light infections can have a larger number of eggs. Adult hookworms are rarely spotted in the stool, due to their small size.

How is feline hookworm infection treated?

Fortunately, treatment is safe, simple, and relatively inexpensive. A deworming medication called an anthelmintic will be administered to kill the adult hookworms. However, most anthelmintics do not kill the larval stages, it is necessary to treat an infected cat again in two to three weeks to kill any new adult worms that were larvae at the time of the first treatment. Ideally, kittens are treated for worms during their kitten vaccination series.

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.

Are hookworms infectious to people?

Adult hookworms do not infect humans internally; however, the larvae can burrow into human skin (usually through bare feet). This causes itching, commonly called “ground itch”, but the worms do not mature into adults and will die within several weeks. 

More dangerous is the condition in which hookworm larvae migrate throughout the human body, damaging the eyes and internal organs. This is called visceral larval migrans. To contract this condition, human skin must have contact with moist, larvae-infected soil, so infection is extremely rare if normal hygiene practices are observed.

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. In addition, prompt deworming should be given if the parasites are detected. Periodic deworming may be appropriate for pets at high risk of infection.
• It is highly recommended that cats use a monthly heartworm preventive that also prevents hookworm infection.
• Ensure prompt disposal of cat feces, especially in yards, playgrounds, and public parks.
• Strict hygiene is important, especially for children. Do not allow children to play in potentially contaminated environments. Be mindful of the risk posed by public parks and sandboxes. Frequent handwashing and bathing are essential in preventing human infections.
• Control of rodents is important since they may play a role in the transmission of hookworms to cats.
• Remove stools from litter boxes daily. Always wash your hands after handling fecal material.