Updated September 25, 2026. Fact-checked against veterinary sources; review by a licensed veterinarian is in progress. See our editorial policy.
Quick answer: Coccidia (usually Cystoisospora species) are microscopic intestinal parasites that commonly infect kittens, especially those from shelters, rescues, or crowded environments. They cause watery or mucousy diarrhea, sometimes with blood, and can lead to dehydration in young kittens. Vets diagnose it with a stool test and treat it with prescription medication. Cleaning up stool promptly is essential, since the parasite eggs are tough and easily re-infect cats. The common cat coccidia don’t infect people.
Signs
- Watery or soft diarrhea, sometimes with mucus or blood
- Straining
- Poor appetite, weight loss, or slow growth in kittens
- Dehydration and lethargy in severe cases
- Adult cats often carry coccidia with no signs
How cats get coccidia
Cats become infected by swallowing mature eggs (oocysts) from contaminated soil, litter, or surfaces, or by eating infected mice and other prey. Stress, crowding, and young age make illness more likely.
When to see a vet
See your vet for diarrhea lasting more than a day in a kitten, or more than a couple of days in an adult cat. Go promptly if there’s blood, vomiting, weakness, or signs of dehydration (sticky gums, sunken eyes), especially in young kittens, who can become seriously ill quickly.
Diagnosis
Your vet will examine a stool sample under the microscope (fecal flotation) to look for oocysts. Because kittens often have more than one parasite, tests for Giardia and worms are also common.
Treatment
- Prescription anti-coccidial medication, such as sulfadimethoxine or ponazuril, as your vet directs.
- Fluids for dehydrated kittens.
- Easily digestible food during recovery.
- Treating other parasites if found.
- Treating other cats in the household if your vet recommends it.
Cleanup to prevent reinfection
- Scoop litter at least daily, since oocysts need time to become infectious.
- Wash litter boxes with very hot water. Oocysts resist many common disinfectants, and steam cleaning or boiling water is effective on hard surfaces.
- Wash bedding in hot water.
- Keep kittens’ rear ends clean.
- Control flies and cockroaches, which can carry oocysts.
- Keep cats indoors to prevent hunting.
Coccidia vs. toxoplasmosis
Toxoplasma is a different, related parasite that can infect people. It’s shed in cat stool only for a short period after a cat’s first infection. Pregnant people and those with weakened immunity should have someone else scoop litter, or wear gloves and wash hands, and litter should be scooped daily.
What to avoid
- Human anti-diarrhea medications, such as Pepto-Bismol or loperamide, which can be unsafe for cats.
- Dewormers alone: common dewormers don’t kill coccidia.
- Stopping medication early because stool looks better.
- Bleach alone as a cleaner: it doesn’t reliably kill coccidia oocysts.
Frequently asked questions
Can people get coccidia from cats?
The Cystoisospora species that infect cats don’t infect people. Toxoplasma is the cat-related parasite of concern for humans.
Can dogs get coccidia from cats?
Coccidia are mostly species-specific, so the cat types generally don’t infect dogs.
How long does treatment take?
Many kittens improve within days. Your vet may recheck a stool sample after treatment.
Sources
- Companion Animal Parasite Council (CAPC): Coccidia guidelines
- Merck Veterinary Manual: Coccidiosis of cats and dogs
- Cornell Feline Health Center: Intestinal parasites
- US Centers for Disease Control and Prevention (CDC): Toxoplasmosis and cats
This article is for general education and is not a substitute for care from your own veterinarian. Learn about The Pet Vet and our editorial policy.