Coccidia are microscopic single-celled parasites that infect a dog's intestines and are a common cause of diarrhea in puppies. In dogs, the disease (coccidiosis) is caused by species of Cystoisospora, formerly called Isospora.1,2 Dogs catch it by swallowing oocysts (the parasite's egg-like stage) from contaminated soil, feces or surfaces, or by eating infected mice or other small animals.1,2 Healthy adult dogs rarely get sick, but puppies, especially stressed puppies recently moved from a breeder, shelter or pet store, can develop watery or mucous diarrhea, sometimes with blood, and become dehydrated.2,1,3 Vets diagnose it with a stool test and treat dogs with signs using an anticoccidial medicine plus supportive care.1,2 Most dogs recover well.2,4 Dog coccidia don't infect people.1,5
See a vet the same day if a puppy has:
- Diarrhea lasting more than a day, or diarrhea with blood or mucus2,4
- Vomiting, poor appetite, lethargy or weight loss2,1
- Signs of dehydration or weakness. Severe coccidiosis can be life-threatening in very young, small or weak puppies.4,1
Puppies with diarrhea should also be checked for parvovirus and other causes. See parvo symptoms.6
What the Research and Guidelines Say
- A puppy problem. A study of 3,590 stool samples, cited in a 2024 review, found 78% of coccidia infections were in puppies in their first 4 months, and only 1% of dogs over a year old were shedding.7
- Breeders are a risk. Puppies from high-volume breeders had about 3.6 times the odds of carrying coccidia in a 2017 Utrecht University study.6
- Treating a whole litter works. At a Spanish breeding kennel, treating 35-day-old puppies with an anticoccidial combined with a dewormer fully controlled coccidia in the kennel, according to a 2024 study.8
- How common it is. CAPC reports coccidia in 3% to 38% of North American dogs, and a 2023 German study found it in 7% of stool samples from dogs in their first year.1,9
How Dogs Get Coccidia
- Swallowing oocysts from feces-contaminated ground, kennels, bedding, food or water. Fresh oocysts aren't infective, but in warm, moist conditions they become infective within hours to days.1,2,3
- Eating mice, rats or other small animals that carry the parasite in their tissues.1,3
- Living in crowded or stressful conditions, such as breeding kennels, shelters and pet stores. Stress from shipping, rehoming or other illness makes disease more likely.1,7
Puppies usually first pick it up between about 3 and 8 weeks of age.5,8
Coccidia vs Eimeria on a Stool Test
Sometimes a stool test shows Eimeria, a type of coccidia that infects livestock, rabbits and birds. Dogs aren't hosts for Eimeria. These oocysts simply pass through after a dog eats another animal's droppings, so they don't need treatment.1,3,2 What they do show is that your dog has been eating feces.
Symptoms of Coccidia in Dogs
Many infected dogs have no symptoms.1,3 Signs, mainly in puppies aged about 4 to 12 weeks, include:3,2
- Diarrhea, which may be watery or contain mucus, and occasionally blood3,2
- Weight loss, poor appetite and lethargy2,1
- Vomiting and dehydration in more severe cases2,1
Disease is usually worse when puppies have other infections at the same time, such as Giardia, worms or viruses.3,7
Diagnosis
Vets find coccidia oocysts with a fecal flotation test under the microscope, and some labs offer PCR testing.1,3,4 Puppies may not shed oocysts early in the illness, so a repeat test may be needed.2,4 Finding oocysts doesn't always prove they're causing the diarrhea, because healthy puppies often carry them too, so your vet will consider other causes.1,6
Treatment
Coccidia need a specific anticoccidial medicine. Routine puppy dewormers don't treat it.2 In the US, one sulfonamide-class medicine is the only drug approved for coccidia in dogs, and vets also use other medicines off-label, including the triazine class, which is the first choice in European guidelines.1,2,5 Courses last several days, sometimes longer or repeated.4 Dehydrated puppies may also need fluids, anti-nausea medicine and a bland diet.2,3
Not every dog needs treatment. Healthy adults that test positive often aren't treated, and mild infections in puppies can clear on their own.2,3 In litters and kennels, though, European guidelines advise treating all the puppies in contact, because this reduces both diarrhea and spread.5,8 Give your dog a bath after the last dose to remove oocysts from the coat.2
How Contagious Is Coccidia?
Coccidia spreads easily between dogs, especially puppies sharing a space.4,7 Puppies start passing oocysts about 6 to 10 days after infection according to European guidelines (Merck gives about 3 weeks), and most shed for 5 to 10 days.5,3 The bigger problem is the environment: oocysts can survive for months, and up to a year in moist, protected places, and they survive freezing.1,4,2 Reinfection is common if the area isn't cleaned.2
Cleaning Up After Coccidia
Coccidia oocysts resist most household disinfectants.1,3 The most reliable steps are:
- Pick up feces at least daily so oocysts don't have time to become infective.1,5
- Scrub hard surfaces with a degreasing cleaner to remove all fecal residue.2
- Steam-clean kennels, crates and floors. Heat is the most widely recommended method.5,3,2
- Let everything dry completely.5
- Control mice and rats and stop dogs from hunting them.1
Some strong ammonia-based products kill oocysts but can only be used with animals removed, and are mainly for kennels.1,3 In a yard, frequent poop pickup is the main control.
Can Humans Get Coccidia From Dogs?
No. The Cystoisospora species that infect dogs are host-specific, so people can't catch them from dogs.1,5,2 Other pets in the home that aren't dogs aren't at risk from dog coccidia either, though other dogs are.5,4
Frequently Asked Questions
Can dogs survive coccidia?
Yes. Most dogs recover well with treatment. Deaths are rare and mainly occur in very young, small or weak puppies.
Can a dog get rid of coccidia on its own?
Mild infections often clear without treatment, but puppies with diarrhea should see a vet.
What naturally kills coccidia?
Heat and drying. No home remedy has been shown to treat coccidia in dogs.
Is coccidia the same as Giardia?
No. Both are single-celled gut parasites common in puppies, but they're different organisms with different treatments. See Giardia in dogs.
Do dewormers treat coccidia?
Standard dewormers don't. Coccidia needs a specific anticoccidial medicine from your vet.
Ask Our Team a Question
Help Others by Sharing Your Dog Story or Question!
Have a Question, Request or Want to Share a Story that could help others? Our team will answer questions for free!
Please include information such as your dog's medical history, age, sex, breed, symptoms, diet, changes in behavior and medications. Providing pictures by uploading them below can also be of help.
We will do our best to get back to you quickly (it depends on how many questions we receive each day). If you do require an immediate response we suggest using this online dog veterinary service that is available now.
Sources and further reading
This article was rewritten and fact-checked on October 23, 2026 against current veterinary references and specialist guidelines:
- Companion Animal Parasite Council. Coccidia: dog recommendations. CAPC guidelines, updated February 2025.
- Cornell Richard P. Riney Canine Health Center. Coccidia in dogs. Cornell University College of Veterinary Medicine, accessed October 2026.
- Andrews A. Coccidiosis of Cats and Dogs. Merck Veterinary Manual, reviewed August 2022, updated August 2026.
- Kearley M. Coccidia in Dogs: Symptoms, Treatment, and Prevention. PetMD, September 2026.
- European Scientific Counsel Companion Animal Parasites. GL6: Control of Intestinal Protozoa in Dogs and Cats, 3rd edition. ESCCAP guideline, March 2025.
- Duijvestijn M. Enteropathogen infections in canine puppies: (co-)occurrence, clinical relevance and risk factors. EVC Voorjaarsdagen proceedings, 2017 (IVIS).
- Grellet A, Mila H. Endoparasitic Diseases in Breeding Kennels: A Frequent and Complex Problem Requiring a Holistic Approach. Animals, 2024.
- Barrera JP, Montoya A, Marino V, Sarquis J, Checa R, Miró G. Cystoisospora spp. infection at a dog breeding facility in the Madrid region: infection rate and clinical management with anticoccidial metaphylaxis. Veterinary Parasitology: Regional Studies and Reports, 2024.
- Murnik L-C, Daugschies A, Delling C. Gastrointestinal parasites in young dogs and risk factors associated with infection. Parasitology Research, 2023.
About this article
Last updated : written using CAPC and ESCCAP parasite guidelines, the Merck Veterinary Manual, Cornell and recent breeding-kennel research, plus International Veterinary Information Service (IVIS) proceedings and research published 2022 to 2026.
This page is for general information and is not a substitute for an exam by your veterinarian.
