Fall is a time to consider cat intestinal parasites, especially outdoor cats. Cats that have access to the outdoors often spend more time outside in the warm seasons in Colorado. During that time they have an increased opportunity to be exposed to and infected by intestinal parasites. This exposure occurs when cats ingest infected rodents or encounter contaminated soil or feces. Signs or indications that a cat is infected can vary from no signs to severe diarrhea and vomiting. When signs are present, they often become obvious in the fall. This is because the intestinal parasite has time to mature through its life stages during the summer and localize in the intestines.

Severity of signs depend on the cat’s overall condition, the specific parasite, and the amount of parasites in their system. These signs can be very nonspecific such as a dull or poor quality hair coat, or more focused on the digestive tract with a change in appetite (reduced appetite or dramatically increased), vomiting, or diarrhea. Rarely, even with heavy infections, parasites like roundworms may be seen in the stool or vomit. Therefore, not seeing them does not mean that the cat is free of roundworms. Usually the parasite seen in the stool in our area is the tapeworm. Tapeworms are small, flat parasites that can be seen on the surface of the stool, under the cat’s tail, or when dried they can look like small pieces of rice stuck to the cat’s hair.

The most common parasites affecting cats in our area are roundworms, tapeworms, coccidia, and giardia. Cats that are indoors exclusively are at a much lower risk unless they live with a cat that goes outside or if they are eating rodents in the house. Keep in mind that an indoor cat can come into a household already infected with parasites.

Certain types of roundworms (Toxocara cati) are passed through the milk from the mom cat to the kittens. For adult cats, hopefully these parasites were identified and treated while a kitten. Roundworm infections from rodents is typically a different roundworm type (Toxascaris leonina). This roundworm infects the cat when the cat eats an infected rodent or the rodents feces. In addition to the health impact of roundworms in cats, they can infect humans. The T. cati infection in humans is more common. This adds increased need to make sure that cats are not infected with roundworms.

Cats can also be infected with tapeworms. Tapeworms have an interesting life cycle that involves what has been termed an intermediate host. This means that certain stages of the tapeworm life cycle occur in a species other than the cat. For example, a cat gets the tapeworm (Dipylidium caninum) from ingesting an infected flea. Fortunately, fleas are not common in our area. However, tapeworms like Taenia taeniaeformis infect cats after eating infected rodents. These are the tapeworms of concern for cats that have been hunting rodents all summer. These do not typically infect humans.

The intestinal parasites in cats can be diagnosed with a stool test or observing the tapeworms on the stool. Once diagnosed, the cat should be treated. Often your veterinarian will recommend treating the other cats in the house at the same time. Treatment is generally straightforward once the type of parasite has been identified. Medications for treating cat intestinal parasites are generally safe and rapidly effective. Alternative deworming approaches like some of the digestive enzyme protocols can take longer and be more difficult to administer. Others like the herbal dewormers should be evaluated for safety in cats prior to use. Daily cleaning of the litter box should be part of the normal routine to reduce recurring exposure. Avoid self contamination when concerned about roundworms and cleaning the litter box or in contact with stool material.

If you have an outdoor cat or any cat that you have concerns about intestinal parasites, contact your veterinarian.

Ron Carsten, DVM, PhD, CVA, CCRT was one of the first veterinarians in Colorado to use the integrative approach, has lectured widely to veterinarians, and has been a pioneer in the therapeutic use of food concentrates to manage clinical problems. He is also the founder of Colorado Animal Rescue (CARE). In addition to his Doctor of Veterinary Medicine, he holds a PhD in Cell and Molecular Biology and is a Certified Veterinary Acupuncturist and Certified Canine Rehabilitation Therapist. He practices integrative veterinary medicine in Glenwood Springs. Dr. Carsten is the 2022 Colorado Veterinary Medical Association Distinguished Service Award recipient.