Threadworms in Cats

Older cats and young kittens have a higher chance for developing this disease due to their weakened or underdeveloped immune systems. However, any cat living in close, unsanitary, and humid quarters is at risk for contracting threadworms.

Threadworms are a rare type of parasitic worm found in a cat’s small intestine. The condition is most likely to occur in unsanitary and crowded environmental conditions, particularly in warm and/or wet climates. While threadworms can also infect humans, the disease is not zoonotic as the parasite found in cats can only spread to other cats.

Threadworms can be life-threatening, especially for younger cats. However, not all infected cats show symptoms. Seek immediate veterinary attention as soon as you notice any of the following symptoms:

• Excessive itching
• Severe diarrhea
• Rapid breathing*
• Fever*
• Blood in the feces
• Abnormalities or worms present in the feces

*When these symptoms are present, the condition has progressed and the prognosis is very poor.

The primary cause of threadworms in cats is infection by the parasite Strongyloides felis or Strongyloides tumefaciens.

Strongyloides felis worms reproduce in the small intestine. The larvae are passed through the feces, where they develop into free-living adults that reproduce once again. These adults require an external temperature of sixty-eight degrees Fahrenheit to reproduce. Their eggs will hatch in about six days, and these larvae are responsible for penetrating the skin and inciting infection.  

The exact life cycle of S. tumefaciens is unknown. However, S. tumefaciens occurs within the large intestine, and may cause the formation of nodules. Infection can occur via ingestion or penetration of the skin.

This parasite often occurs in unsanitary conditions, and spreads rapidly when cats are living in close quarters, such as unclean kennels. Threadworms are more commonly found in India and Australia, but may occur in humid areas of the United States such as Florida, Texas, Louisiana, and Georgia.

Your vet will be able to make a tentative diagnosis based on a thorough physical examination and presentation of symptoms. Be sure to inform your vet of the extent and duration of your cat’s symptoms, as well as any relevant travel history or unsanitary environmental factors that you know of.

Your vet will make a definitive diagnosis by utilizing a technique known as fecal flotation. This involves mixing a sample with a solution which will separate the eggs and cause them to float to the top. The vet then places the separated eggs onto a slide and examining them using a microscope. The number of eggs present typically correlates to the severity of the infection.

Your vet may also take a skin scraping if excessive itching has occurred. Do not submit your own stool samples to the vet unless specifically instructed to do so. Your vet will require a fresh stool sample for examination.

Treatment for threadworms is typically straightforward in mild cases, and generally involves deworming medications. These medications may vary depending on the specific parasite present. Medications include ivermectin, mebendazole, fenbendazole or thiabendazole. Some of these medications may not be suitable for certain breeds, and some have not been approved by the FDA to treat threadworms specifically. (However, it should be noted that all medications listed are approved for use in treating several types of worms.) These medications may be prescribed from three days to several weeks.

Treatment methods may vary in cats with weakened or underdeveloped immune systems. Your vet will be able to advise you on a treatment plan and dosage instructions based on your cat’s specific needs.

Recovery and prognosis are generally good provided that the condition has not progressed and an unsanitary environment is cleaned up and disinfected. Always follow your vet’s post-treatment instructions carefully. Always administer any prescribed medications exactly as directed. Do not use any over-the-counter worming medications unless specifically instructed to do so by your vet. These may not be suitable for treating threadworms in cats.

It is imperative that you maintain a sanitary environment for your cat to prevent reinfection. If you live in a multi-cat household, you will need to isolate any infected cats, particularly those that have diarrhea. Avoid exposing any affected cats to direct sunlight or high temperatures. Clean the surfaces of your home using steam or a lime or salt solution followed by a hot water rinse. Thoroughly disinfect any kennels you are using.

Your vet will schedule follow-up appointments every six months in order to confirm the infection hasn’t recurred. If you have any questions, or if the condition has recurred or seems to be getting worse despite treatment, contact your vet immediately.