A little clarity. A lot of love.
AI DiagAnimalsMADE FOR THE ONES YOU LOVE
English

Language and region

Understand their results
Menu
DISEASE · DOGS

Coccidia in dogs: the fecal test, puppies and oocysts

Coccidia are tiny single-celled parasites of the gut. In dogs they belong to the genus Cystoisospora and mostly cause diarrhea in young puppies, often in kennels and breeding facilities. The fecal test finds their oocysts, but a positive or negative result always needs to be read with the puppy’s age and signs.

Written by the AI DiagAnimals editorial teamReviewed by the AI DiagAnimals TeamUpdated Our editorial policy

The essentials

Coccidiosis is mainly a disease of puppies: most clinical cases are seen at 2 to 4 months of age. The vet finds the oocysts with a fecal flotation, or with an antigen or PCR test. Diarrhea can start 2 to 3 days before oocysts appear in the stool, so an early test can be negative. Finding oocysts does not prove they cause the diarrhea: parvo, Giardia and other causes may need to be ruled out. Blood work does not diagnose coccidia, but it shows dehydration.

Have your puppy’s results in front of you? Get every value explained in plain language. Upload the report

What coccidia are and how dogs get them

The common dog species are Cystoisospora canis and the C. ohioensis-complex (C. ohioensis and C. burrowsi, which cannot be told apart under the microscope) [1]. They are host-specific: dog coccidia do not infect cats, and they are not considered a risk for people [1, 2].

Dogs swallow mature (sporulated) oocysts from a contaminated environment, or eat a prey animal such as a mouse that carries resting stages [1, 2]. Oocysts stay infective for many months and can build up in breeding kennels [1, 2]. In moist, protected places they can survive up to one year [2].

First infections usually happen while puppies are still nursing, between 3 and 8 weeks of age, so most sick puppies are 2 to 4 months old [1]. In a study of 3,590 Austrian dogs up to 2 years old, 8.7% shed oocysts, and 78% of those were puppies up to 4 months [4]. In 24,677 German fecal samples, oocysts were found in 5.6% of all dogs but in 23.4% of dogs up to 3 months old [5]. Puppies from high-volume breeders had 3.6 times the odds of carrying Cystoisospora [7].

Signs, and what coccidia poop looks like

  • Diarrhea in puppies, from soft to watery; in severe cases the stool contains blood [1, 2].
  • Weight loss and dehydration; very sick puppies may stop eating, vomit and seem depressed [2].
  • Triggers: a change of diet such as the first solid food, stress from transport or a new home, or another illness can make it worse [1, 2].
  • No signs at all is also common: many dogs shed oocysts without being ill [1, 2].

Stool appearance does not identify the cause. In one study, fecal consistency varied a lot between puppies, whatever the number of oocysts they received [4].

How the fecal test finds coccidia

An annotated line from a lab report · Illustrative example
AbbreviationResultUnitLaboratory intervalFlag
Flotation Fecal flotation (centrifugal)Cystoisospora oocysts seen–None seen–
  1. Abbreviation Fecal flotation, fecal float or O&P. Some reports name the species (C. canis or C. ohioensis-complex), which the lab tells apart by oocyst size [1].
  2. Result Oocysts seen in this illustrative line. Some labs add a count, such as oocysts per gram (OPG); in puppies counts ranged from 333 to 35,000 OPG in one breeding unit [4].
  3. Unit No unit for a seen/not seen result. A count is given per gram of feces.
  4. Laboratory interval The expected result is “none seen”. A negative result early in the illness does not rule coccidia out [3].
  5. Flag Often no H or L flag on a fecal result. A positive line is read with age and signs: oocysts alone do not prove they cause the diarrhea [2].
  • Fecal flotation: a concentration flotation, ideally with centrifugation and enough stool, shows the oocysts under the microscope [1, 2]. C. canis oocysts are about 39 × 32 µm, those of the C. ohioensis-complex about 24 × 20 µm [1].
  • Antigen test: detects Cystoisospora proteins in stool. Against flotation, one assay agreed on 88.5% of positives and 98.2% of negatives, and found more positive puppies (7.4% vs 3.6%) [9].
  • PCR: detects the parasite’s DNA. CAPC advises combining antigen or PCR tests with a microscope exam of the stool [2].

Reading a positive or negative result

  • Negative too early: the prepatent period (from infection to the first oocysts) is 6 to 10 days [1]. In puppies infected with C. canis, diarrhea began 2 to 3 days before oocysts appeared, so a repeat test may be needed [3].
  • Short shedding: most dogs shed oocysts for only 5 to 10 days [1].
  • Counts and disease: C. canis gives higher counts and longer shedding than C. ohioensis [4], but a high or low count does not on its own say how sick the puppy is. After a reinfection, dogs usually shed few oocysts and show no signs [1].
  • Look-alike oocysts (pseudoparasites): dogs that eat feces or prey can pass Eimeria oocysts. Dogs are not hosts for Eimeria, and the lab can tell them apart [2]. In 48,509 fecal exams, Eimeria oocysts were the most common “spurious” finding (4.14%) [8].

Other causes of puppy diarrhea to rule out

Puppies often carry several gut pathogens at once. In a Dutch study, pathogens were found in 86.5% of puppies with diarrhea and 77.8% of healthy ones; only parvovirus and canine coronavirus were clearly linked to diarrhea, and parvovirus and Cystoisospora were often found together [7]. The authors advise testing puppies with acute diarrhea for parvovirus [7].

Giardia is also common at the same age: in German puppies, Cystoisospora and Giardia together were found in 28% of samples in the 6th week of life [6]. In a study of 117 young dogs with diarrhea, the same fecal exams also found Giardia, hookworms and roundworms [13].

What the blood work shows

Blood tests do not diagnose coccidia. They show how dehydrated the puppy is and help rule out other causes.
TestPossible findingWhat it means
Hematocrit (PCV)High or falsely normalWater loss concentrates the blood; it can hide an anemia [11].
Total protein and albuminHighFluid losses concentrate the proteins in the blood [14].
Urea (BUN)High, sometimes with a normal creatinineLow blood volume slows flow through the kidneys, so more urea goes back into the blood; bleeding in the gut can also raise urea [12].

See the CBC for dogs and BUN in dogs.

Outlook and prevention

Many infected dogs never get sick, and after a first infection reinfections are usually mild [1, 2]. Severe cases can be fatal: in one experimental study, 4 of 6 untreated puppies died by day 12 [10]. Because litter mates are at high risk even before they shed oocysts, vets usually treat all in-contact puppies [1].

Daily removal of feces helps, because oocysts become infective quickly [2]. Infective oocysts resist most common disinfectants; ESCCAP names heat (steam cleaning) and cresol-based disinfection, and CAPC notes that strong ammonia products can destroy them [1, 2]. Letting surfaces dry completely also helps [1].

Related articles

En français : coccidiose du chien.

Questions to ask your veterinarian

  1. Which species was found: C. canis or the C. ohioensis-complex?
  2. Could the test be negative because it was done too early? Should we repeat it?
  3. Should we also test for parvo and Giardia?
  4. Is my puppy dehydrated on the blood work?
  5. Do the other puppies of the litter need care, and how should we clean the area?
YOUR PET’S FULL REPORT

Get your puppy’s fecal and blood results explained together.

AI DiagAnimals reads the fecal results, blood count, urea and creatinine together with your laboratory’s intervals, and prepares the questions for your vet. The service opens soon: leave your email to be told first.

Explain my puppy’s reportSee a sample report

Frequently asked questions

How did my dog get coccidiosis?

By swallowing mature oocysts from a contaminated environment, often in the litter area while nursing, or by eating prey such as mice that carry resting stages [1, 2].

What does coccidia poop look like?

It ranges from soft stool to watery diarrhea, sometimes with blood in severe cases [1, 2]. The look of the stool cannot confirm coccidia: only a fecal test can.

What happens if coccidia goes untreated?

Many dogs shed oocysts without signs, but puppies can develop severe diarrhea with weight loss and dehydration, and death is possible [1, 2]. In one experimental study, 4 of 6 untreated puppies died [10].

Can dogs recover from coccidia on their own?

Shedding usually lasts 5 to 10 days, and many infected dogs stay healthy [1, 2]. Puppies with diarrhea should still be seen by a vet, because severe cases can be fatal and other causes such as parvo need to be ruled out [2, 7].

Can I catch coccidia from my dog?

No. Dog Cystoisospora species are host-specific and are not considered a risk for people [1, 2].

Sources

  1. ESCCAP. Guideline 06: Control of Intestinal Protozoa in Dogs and Cats, 3rd edition, March 2025. esccap.org/guidelines/gl6
  2. Companion Animal Parasite Council (CAPC). Coccidia (dog). Updated February 2025. capcvet.org/guidelines/coccidia
  3. Mitchell SM et al. Cystoisospora canis Nemeséri, 1959 (syn. Isospora canis), infections in dogs: clinical signs, pathogenesis, and reproducible clinical disease in beagle dogs fed oocysts. J Parasitol. 2007;93(2):345-352. doi.org/10.1645/GE-1024R.1
  4. Buehl IE et al. Canine isosporosis – epidemiology of field and experimental infections. J Vet Med B Infect Dis Vet Public Health. 2006;53(10):482-487. doi.org/10.1111/j.1439-0450.2006.00973.x
  5. Barutzki D, Schaper R. Results of parasitological examinations of faecal samples from cats and dogs in Germany between 2003 and 2010. Parasitol Res. 2011;109 Suppl 1:S45-S60. doi.org/10.1007/s00436-011-2402-8
  6. Barutzki D, Schaper R. Age-dependant prevalence of endoparasites in young dogs and cats up to one year of age. Parasitol Res. 2013;112 Suppl 1:119-131. doi.org/10.1007/s00436-013-3286-6
  7. Duijvestijn M et al. Enteropathogen infections in canine puppies: (co-)occurrence, clinical relevance and risk factors. Vet Microbiol. 2016;195:115-122. doi.org/10.1016/j.vetmic.2016.09.006
  8. Nagamori Y et al. Prevalence of spurious parasites identified in feces of dogs and correlation with true canine parasitism. Vet Parasitol. 2025;336:110466. doi.org/10.1016/j.vetpar.2025.110466
  9. Porter AL et al. Analytical validation of an immunoassay for the detection of Cystoisospora spp. coproantigen in canine and feline fecal samples. J Vet Diagn Invest. 2026;38(1):130-134. doi.org/10.1177/10406387251385940
  10. Daugschies A et al. Toltrazuril treatment of cystoisosporosis in dogs under experimental and field conditions. Parasitol Res. 2000;86(10):797-799. doi.org/10.1007/s004360000217
  11. eClinPath, Cornell University College of Veterinary Medicine. Hematocrit. eclinpath.com/hematology/tests/hematocrit
  12. eClinPath, Cornell University College of Veterinary Medicine. Urea. eclinpath.com/chemistry/kidney/urea-nitrogen
  13. Morelli S et al. Occurrence of Cystoisospora spp. and other intestinal parasites in dogs and cats with diarrhea. Vet Parasitol. 2025;338:110546. doi.org/10.1016/j.vetpar.2025.110546
  14. eClinPath, Cornell University College of Veterinary Medicine. Total protein. eclinpath.com/chemistry/proteins/total-protein

Laboratory methods and reference intervals vary. This article explains; it does not diagnose. For a decision about your pet, use the original report and talk to your veterinarian. Our editorial policy.

Cookie Policy