Roundworms are ingested as eggs or passed from pregnant or nursing mothers to their young. The larvae then migrate throughout the body, returning to the intestines in adulthood. While roundworms are usually easy and inexpensive to treat, untreated cats can experience great discomfort as well as vomiting and diarrhea, and untreated kittens and older cats can face life-threatening malnutrition and pneumonia. If you suspect that your cat may have roundworms, make an appointment with your veterinarian immediately.

Roundworms are the common name for several species of intestinal parasites that can infest cats, dogs, humans, and many other animals. However, in regard to cats, the term “roundworm” refers specifically to Toxascaris leonina and Toxocara cati. Collectively, roundworms are also sometimes referred to as ascarids or ascaridoid nematodes. Roundworms average between three and six inches in length in adulthood and “swim” within the intestines of the infected animal. While cats of any age can become infected by roundworms, kittens, pregnant females, cats that hunt and older cats are particularly susceptible to roundworm infestation. The disease that is caused by roundworm infection is ascariasis.

Kittens, pregnant and nursing females, outdoor cats that hunt rodents and birds, and older cats are especially susceptible to infestation by roundworms. If you observe the following symptoms in your cat, even if your cat does not fit into any of the aforementioned categories, contact your veterinarian to make an appointment. If the symptoms are caused by roundworm infestation, you will need to begin the deworming process immediately for the sake of your cat’s health and the health of others, including your family.

In addition, some cats that are carrying small numbers of roundworms may not show any symptoms. If you have any reason to suspect that your cat may have been exposed to roundworm eggs, contact your veterinarian.

There are four main ways that a cat can become infested with roundworms. 

All kittens, when they reach the age of two or three weeks, should be examined by your veterinarian, who will determine if they, and possibly their mother, should receive deworming medications as a precaution. By doing so, many cases of roundworm infestation can be prevented. In addition, all cats, but especially those that are kittens, pregnant females, hunters, or older cats, that present the symptoms listed above or that have come in contact with animals that may be infected should be examined by a veterinarian. If possible, take a recent fecal sample in a sealed bag or container with you to the veterinarian’s office. The veterinarian will often diagnose roundworms by following these steps:

Examine the fecal sample you have brought in and/or take a fecal swab from your cat.

Treatment for roundworms is usually both simple and fairly inexpensive. All kittens should be examined by your vet for possible deworming treatment, as should pregnant or nursing females. The vet may prescribe that your kittens are dewormed at three, five, seven, and nine weeks of age. For any cat that is diagnosed with ascariasis, your veterinarian will likely prescribe anthelmintic deworming medications. Because these medications can only kill adult roundworms, your veterinarian may prescribe multiple rounds of treatment spread out over two to three-week intervals to allow any larvae to mature into adults that can then be killed by the anthelmintic medication. Your vet will likely instruct you to clean the cat’s home environment, especially the litter box and surrounding area, with a solution of bleach and water. 

Unless the roundworms have gone undiagnosed and/or untreated long enough to cause more serious health problems, otherwise healthy kittens and cats that receive deworming treatment will likely have a good prognosis. Most cats will recover completely, but preventative measures, such as removing feces from litter boxes and outdoors, must be taken to avoid repeated infection. In addition, it should be noted that some heartworm treatments are also able to prevent roundworms as well, which may be an effective way to prevent infection or avoid re-infestation.