While the thought of your cat having worms can be upsetting, it’s surprisingly common. Infection rates are known to be as high as 33%.¹ That is why taking your cat to your veterinarian and using parasite prevention is so important. Whether your cat is indoor or outdoor or a former stray or purebred, knowing a bit about worms is an important part of caring for your cat.

Types of Worms That Can Infect Cats

Common gastrointestinal worms that affect cats include roundworms, tapeworms, and hookworms. Heartworms are another type of worm that can infect cats, impacting their heart and lungs.

Roundworm

The most common intestinal worm is roundworm.² Almost all cats will be infected with roundworms at some point in their life, usually when they are kittens.³ While they may cause more mild disease in adult cats, they can be life-threatening in large numbers for kittens. These large-bodied worms live freely in the intestines. They average 3–6 inches in length.

Tapeworms

Tapeworms anchor themselves to the intestines with hook-like mouthparts. Individual tapeworm segments break off as the worm matures and are passed in the cat’s poop. The most common type of tapeworm that infects cats is the flea tapeworm, which is spread by fleas. If your cat has a tapeworm infection, you might notice these segments—they can look like grains of rice on your cat's poop or fur.

Hookworms

Hookworms affect cats worldwide, especially in warmer, moist climates. These tiny worms have hook-like mouth parts that secure them to the lining of the intestinal wall. Once attached to the intestine, hookworms suck blood and can cause anemia. Kittens are at highest risk of significant blood loss from hookworm infections.^5,6

Heartworm

Heartworms can cause serious disease in cats and are often underdiagnosed. Cats can become infected when they are bitten by a mosquito carrying heartworm larvae. Typically, cats with heartworm infections only have one or two worms, but even a single worm can cause serious damage to the cat's heart and lungs.

How Do Cats Get Worms?

This depends on the type of worm that infects your cat.

Roundworms

Cats become infected with roundworms by eating infected rodents or ingesting roundworm eggs present in feces or contaminated soil. A mother’s milk can be infected with larvae which are then passed to kittens during feeding.

Tapeworms

As you might guess, flea tapeworms require fleas to be transmitted. Cats become infected with flea tapeworms after they eat a tapeworm-infected flea, as might commonly occur during grooming. The tapeworm eventually begins releasing egg packets, into the cat's feces. Flea larvae in the cat’s environment can eat these tapeworm egg packets and the cycle begins again.

Cats can become infected with other types of tapeworms by prey animals, like mice.

Hookworms

Hookworm infection in cats can occur when the larvae enter the body through the cat’s skin or via ingestion during grooming.

Heartworms

Cats can become infected with heartworms when they are bitten by a mosquito that is carrying heartworm larvae. Even indoor-only cats can be at risk for heartworm disease because mosquitoes can come indoors.

Signs Your Cat Might Have Worms

The signs cats exhibit with intestinal worms are nonspecific. This means they’re general signs, not indicative of a specific cause. These signs of worms in cats can include any of the following:

Signs of Gastrointestinal Worms

• Vomiting
• Diarrhea
• Mucous in stool
• Bloody stool
• Constipation
• Loss of appetite
• Pale gums
• Bloated belly
• Weight loss
• Dehydration
• Coughing
• Dull coat
• You may actually see them!

Young kittens, injured cats, or those with weakened immune systems are more likely to experience severe disease and symptoms from intestinal worms. For example, roundworms can cause stunted growth and development in kittens. Hookworms can cause anemia. Intestinal blockage can result from an accumulation of high numbers of tapeworms.

Signs of Heartworm Disease in Cats

• Coughing
• Trouble breathing
• Vomiting
• Sudden death
• Some cats may show no signs at all

Treatment of Worms in Cats

There are several types of deworming medications that are used to treat intestinal worms in cats. Your veterinarian will determine the best option based on your cat’s specific worm infection. Multiple doses of a deworming medication may be needed depending on the type of intestinal worm.

There is no treatment for heartworm disease in cats. The best way to protect your cat is to keep them on monthly heartworm prevention all year round.

If cats are symptomatic for worms, additional medications may be necessary to treat and manage those signs.

How a Parasite Preventative Can Protect Your Cat Against Worms

The best way to protect cats against worms is by being proactive. Providing your cat with a monthly broad-spectrum preventative (also called a parasiticide) can easily protect against dangerous parasites, including heartworms, roundworms, hookworms, and tapeworms.

Your cat should be tested for parasites every six to 12 months and kittens may need to be tested for gastrointestinal parasites more frequently. Regular wellness visits with your veterinarian are also important to ensuring your cat stays happy and healthy!