Diseases Caused by Worms in Cats

Several health risks can be associated with infection of worms in cats. Cats are susceptible to many different types of parasitic infections such as heartworms, hookworms, roundworms, tapeworms, whipworms and ringworm (which isn't actually a worm, but a fungus.) Many of these worms may cause further health problems in cats and should be treated immediately.


Heartworms are uncommon in cats, but can easily be passed by an infected mosquito. Heartworms are large worms that live in a cat's heart and can eventually cause death. Heartworms may cause a disease called 'HARD' or 'heartworm associated respiratory disease.' These worms affect the respiratory system by passing through the blood vessels into the lungs. Most of them will die in the lungs and cause sudden inflammation leading to the following symptoms:

  • Coughing
  • Difficulty breathing
  • Vomiting
  • Rapid heart rate
  • Collapse
  • Convulsions
  • Blindness
  • Sudden death with no other visible symptoms


Hookworms are passed when cats ingest hookworm eggs, which can live in the soil for months. Eggs are not visible to the naked eye, so are difficult to detect. These worms use hook-like mouth parts to attach themselves to the intestinal lining and feed off the tissues. Symptoms of infestation can include blood in the stool, weight loss and a poor haircoat. This parasitic infection can lead to anemia, as hookworms will sometimes suck the blood, leading to a continued loss into the bowels.


Roundworms are most commonly passed from adult mother cats to their kittens through the mammary glands. Kittens are at highest risk for health concerns related to roundworm infection, but adult cats can be infected by ingesting eggs from infected feces or intermediate hosts such as earthworms or rodents. Roundworm infection is called 'ascariasis' and generally does not produce symptoms in adult cats. Kittens may appear to be pot-bellied, have a decreased appetite, vomiting, diarrhea, abdominal discomfort and poor growth. 


Tapeworms in cats are the most common of the parasitic infections, and are also the least harmful. These worms are passed by ingesting an infected flea. Generally, this condition is identified by detection of live worms in the feces, or rice-like matter attached to the fur near the anus. A cat may drag his anus across the floor due to irritation of the area. If tapeworms pass into the cat's stomach, an adult tapeworm several inches long may be vomited. No additional diseases are generally associated with tapeworm infection in cats.


Whipworms are contracted by ingesting food or water infected with live eggs. This worm feeds on the blood by attaching itself to the intestinal wall. While symptoms of infection are rare in cats, occasionally blood in the stool and/or anemia may result.


Ringworm is not actually a worm but a fungus that affects the skin, hair and nails of a cat. Symptoms of this infection usually result in loss of hair around a small, round lesion. This lesion may continue to grow and could be itchy or irritable. Ringworm can also affect the growth of the nails. Ringworm generally does not cause additional disease and is often cured on its own by the immune system. If signs develop, it may be necessary to check for underlying conditions causing compromise of the immune system.