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Coccidia In DogsUpdated 10 months ago

Coccidia are one celled intestinal parasites known as a protozoa and are only visible under a microscope. Infections are possible in dogs of all ages but are more common and serious in puppies. May cause watery or bloody diarrhea.

My Dog Tested Positive For Coccidia

Finding the spores (oocysts) of coccidia in your dog’s stool sample very likely means your dog is infected with coccidia and may need to be treated. Healthy dogs with strong immune systems might clear or suppress a coccidia infection on their own and some veterinarians may hold off treating in certain cases. Puppies, on the other hand, are almost always treated because coccidiosis can become life threatening to these young dogs. A test result is not the same as a veterinarian’s diagnosis, so it’s always best to consult with a veterinarian about your dog’s test results to determine the safest and most effective treatment and prevention plan, and when to do follow-up stool tests.

MySimplePetLab Routine Dog Stool Tests report positive coccidia results using a quantitative estimation scale of 1 (1 egg or parasite was seen), 1+ (2 to 4 eggs or parasites were seen), 2+ (5 to 10 eggs or parasites were seen), 3+ (11 to 50 eggs or parasites were seen), or 4+ (>50 eggs or parasites were seen) per (approximately) one gram of stool. This is based on a microscopic exam of the stool after special preparation and centrifugation techniques. This scale provides some perspective on the potential burden of coccidia infection (more oocysts likely means more coccidia in the intestines).

Most veterinarians will recommend rechecking a dog’s stool sample 2-4 weeks after treatment for coccidia. If you have other dogs in the household, they should be tested as well.

Sometimes the type of coccidia detected in dog stool is Eimeria spp., which is NOT harmful to dogs, cats, or people. Eimeria spp. infects and passes in the stool of rabbits, rodents, poultry, farm animals (cattle, sheep, goats), and wildlife. Treatment is generally not necessary.

My Dog Tested Negative For Coccidia

If your dog had a stool O&P (fecal ova and parasite) test and coccidia were not seen, that is great news. It may mean that you are doing a good job preventing coccidia infections by maintaining good cleanliness of the indoor and outdoor areas, or you and your dog were just lucky! Either way no one wants their dog shedding coccidia into the home or community environment, putting other dogs at risk of infection or your dog at risk of re-infection. Most veterinarians recommend retesting your adult dog for coccidia every 6 to 12 months.

Keep in mind that it’s possible for dogs to have coccidia without their spores (oocysts) being found in the stool test (called a “false negative” result); especially if the infection is mild (very small number of coccidia) or is recent (coccidia are not yet shedding oocysts). Also depending on their lifestyle, dogs can remain at risk of coccidia exposure so a negative test result today doesn’t mean it couldn’t be positive later. This explains why regularly testing for coccidia (1-2 times per year in adult dogs; 3-4 times for puppies) is most often combined with good hygiene (cleaning up dog stool quickly) throughout the dog’s life.

Learn More About Coccidia

What Are Coccidia?

Coccidia are a microscopic group of spore-forming protozoa. They are not ‘worms’, at least not in the traditional sense like roundworms, hookworms, tapeworms, and whipworms. They are also not susceptible to “deworming” medications. Coccidia get grouped together with “worms” because they are routinely searched for in stool tests for worms (fecal ova and parasite test). With the naked eye you won’t ever see coccidia in your dog’s stool. This is because all stages of their life are microscopic.

Dogs can get infected with many different types (species = spp.) of coccidia (Cystoisospora spp., Hammondia spp., Sarcocystis spp., Neospora spp., and Cryptosporidium spp.). The most common and important type of coccidia in dogs is Cystoisospora (previously called Isospora), which includes four species that infect dogs (C. canis, C. ohioensis, C. burrowsi, and C. neorivolta).[3] While not often a major concern for healthy adult dogs, Cystoisospora coccidia can cause severe (sometimes life-threatening) diarrhea in puppies and in adult dogs with suppressed immune systems.[3]

Sometimes the type of coccidia detected in dog stool is Eimeria spp., which is NOT harmful to dogs, cats, or people. Eimeria spp. infects and passes in the stool of rabbits, rodents, poultry, farm animals (cattle, sheep, goats), and wildlife. Treatment is generally not necessary.

The other types of coccidia are less likely to cause sickness in dogs and less common to find in routine stool analysis (fecal ova and parasite test). Some types are rare today because dogs can only get infected by eating the raw meat/tissues from infected cattle, sheep, goats, rabbits, horses, pigs, deer, etc. Blood tests are sometimes necessary to uncover these less common causes of coccidiosis. The type of coccidia we are most concerned about finding in dog stool samples are Cystoisospora spp.[3,6]

How Common Are Coccidia?

Coccidia are routinely searched for and commonly found in stool tests of dogs, especially puppies. Infected dogs may not show symptoms but still spread spores (oocysts) into the environment,[1] posing a re-infection risk for themselves and a new infection risk for other dogs. Infective coccidia oocysts are resistant to common disinfectants and with the right temperature and humidity, last many months indoors (kennels, runs, cages) and outdoors.[3]

Young animals are more likely to get infected and show symptoms.[3] Dogs and puppies that are immune-suppressed, fighting off other infections, and/or in stressful conditions (like being transported/relocated or housed in groups) are more likely to get sick with coccidiosis (diarrhea, vomiting, poor appetite).[3,6]

What Do Coccidia Look Like?

All life stages of coccidia are too small to be seen by the naked eye. Some life stages of coccidia can only be seen by biopsy of the intestine and microscopy, so it’s best to search for the oocysts of coccidia in stool samples under a microscope (MySimplePetLab Routine Dog Stool Test).

Under the microscope, coccidia spores (oocysts) are smaller and more transparent than the eggs of actual parasite worms (roundworms, hookworms, tapeworms, whipworms), so require experience and careful evaluation to find.[1] While often referred to as “eggs”, they are actually spores which have a different appearance under the microscope if they are non-infective (immature, unsporulated oocyst) versus infective (mature, sporulated oocyst). The infective spores have tiny single-celled stages within them called sporozoites and are released when the spores reach the intestines of the dog after being swallowed.

What Symptoms Are Caused By Coccidia?

Most dogs infected with coccidia appear as normal, healthy dogs. Their immune systems can keep coccidia numbers low, so the intestinal damage is mild and easily repaired. These dogs probably don’t have or only rarely have abnormal stools (like diarrhea).

However, if their health situation changes then dogs can become sick from coccidia (called coccidiosis). Dogs and puppies that are immune-suppressed, fighting off other infections, and/or in stressful conditions (like being transported/relocated or housed in groups) may be unable to keep the coccidia in check.[3,4

When dogs do get sick from coccidia, the symptoms can range from mild to serious and mimic signs of other intestinal diseases. These parasites are most dangerous and can be life-threatening in puppies. Clinical signs from coccidiosis are the result of damage to the intestines and may include:[1,3,4]

  • Mucous diarrhea
  • Bloody diarrhea
  • Vomiting
  • Lack of appetite
  • Dehydration
  • Abdominal distress (discomfort)
  • Weight loss
  • General weakness
  • Death (puppies)[1,3,4]

If your dog is acting sick, please contact a veterinarian right away.

How Do Dogs Get Coccidia?

Dogs become infected with Cystoisospora canis coccidia by accidently swallowing their infective spores (oocysts) from the environment.[1,3,4]  Coccidia oocysts are resilient to disinfectants and can survive for many months (up to one year) indoors within a kennel, shelter, or household, or outdoors for the same amount of time if the temperature and humidity are right.[1,3]

Coccidia contaminate the indoor or outdoor environment from the stool of an infected dog. The coccidia can then re-infect the same dog or infect new dogs when the infective oocysts are swallowed from licking the floor or toys, by eating soil, grass, or plants, or drinking water that had been contaminated with coccidia.

Puppies are more likely to get infected than older dogs.[3] Dogs that are immune-suppressed, fighting off other infections, and/or in stressful conditions (like being transported/relocated or housed in groups) are more likely to get sick with coccidiosis (diarrhea, vomiting, poor appetite).[3]

What Is The Coccidia Lifecycle?

Cystoisospora canis coccidia start their life as immature spores (called unsporulated oocysts) which are shed within the stool of an infected dog. A spore is reproductive cell that is quite resilient in moist conditions (indoors or outdoors) and can survive one year if not too hot (>100 degrees F) or too cold (freezing).[3]  Kennels, shelters, day cares, and home environments can stay contaminated with coccidia for long periods of time.

In the right conditions, the immature spores will rapidly mature and sporulate (within 1 day) to become infective.[3] This means that microscopic, motile sporozoites developed within the oocyst. After getting swallowed, these sporozoites get ‘hatched’ from the oocyst in the dog’s intestines. They then invade the cells of the intestines to reproduceand release the next generation of immature oocysts.[1] Once in the environment, the immature oocysts mature and may get swallowed to re-infect the same dog or infect a new dog.

It’s the activity of coccidia in the lining of the intestines which damages or bursts cells. With enough damage, symptoms are seen like watery or bloody diarrhea. [1,2]

Can People Or Other Pets Get Coccidia?

Most coccidia are host-specific. This means that dog coccidia infect dogs, cat coccidia infect cats, and human coccidia infect humans. Yes, people have their own versions of coccidia (Cystoisospora belli, Cyclospora cayetanensis, and several Cryptosporidium spp.).[5]

While dogs can easily spread coccidia to other dogs, don’t be concerned about your cat or human family getting infected from the common types (Cystoisospora spp.) of dog coccidia.[2,3,5,6] Once in a while, dog coccidia will be found in a cat’s stool test or vice versa. This means that the cat swallowed the dog coccidia or the dog swallowed the cat coccidia (maybe by eating infected cat stool). Neither can infect the other and the coccidia just pass through harmlessly.[3]

An exception that needs mentioning is “Crypto” (short for Cryptosporidium). Versions of this coccidia can potentially jump between animals and people. Cryptosporidium canis (dogs) and Cryptosporidium felis (cats) can infect humans, but only rarely in people with compromised immune systems.[3,5]Cryptosporidium parvum is not as host-specific. It can infect and be shed in the stool of animals and people. This is usually the type of coccidia responsible for getting people sick (watery diarrhea, stomach cramps, nausea, vomiting) when municipal water supplies or recreational water sources are contaminated.[1,3,5]

Sometimes the type of coccidia detected in dog stool is Eimeria spp., which is NOT harmful to dogs, cats, or people. Eimeria spp. infects and passes in the stool of rabbits, rodents, poultry, farm animals (cattle, sheep, goats), and wildlife. Treatment is generally not necessary.

How Are Coccidia Prevented And Treated?

Preventing coccidia is first and foremost about hygiene. Coccidia ‘eggs’ (oocysts) can become infective quickly once passed in the dog’s stool, so daily removal of stool is the best way to prevent exposure. This includes thoroughly cleaning indoor areas where dog stool has been present.[1] Steam and pressure washing may help to dislodge stool particles from kennel and cage surfaces. Painting and sealing kennel floors will help prevent stool from adhering to these surfaces while cleaning.[3]

Equally important is understanding (through stool testing) which dog(s) or puppies are infected with coccidia and treating them, if appropriate. Healthy adult dogs with strong immune systems may not require treatment if they can clear or suppress the coccidia infection on their own. However, the risk of infection to other dogs that live in the same household, or to other dogs in the community needs to be considered. Puppies are almost always treated since coccidia can become life-threatening at that age.

The most common treatment is sulfadimethoxine, which is approved to treat enteritis (intestinal inflammation) caused by coccidia. This is an antibiotic and likely will require a veterinarian prescription for purchase. In some cases, a veterinarian may recommend other treatments if the signs are severe or the first treatment isn’t working.[1,3,4]

Where Are Coccidia Medications Purchased?

While MySimplePetLab does not dispense or prescribe medications, there are treatment medications available over-the-counter (OTC) and through veterinarians for coccidia treatment. The most common treatment for coccidiosis (infection with coccidia) is a sulfa-type antibiotic like sulfadimethoxine or trimethoprim/sulfonamide.[1,3] Note that purchasing an antibiotic usually requires a veterinarian’s prescription. Consideration should be given to the risk of developing antibiotic resistance with improper or overuse of antibiotics.

It’s always best to consult with a veterinarian prior to administering any medication, even an OTC version, to make sure it will be safe and effective for your pet. Always read the medication administration directions carefully and be on the lookout for potential side effects (like vomiting) when any medication is administered.

When/How Is Dog Stool Tested For Coccidia?

Veterinarians recommend stool (fecal) testing puppies 2 to 4 times during their first year of life, and 1 to 2 times each year in adult dogs (every 6 to 12 months).[2,3] Veterinarians often call this stool test a “Fecal O&P”, with the O&P meaning “ova (eggs) and parasites”. It includes special preparations of the stool sample and analysis using a microscope to look for certain types of parasites like coccidia. This same test is also used to recheck stool samples after treatment. Typically, a “recheck” stool test is done 2-4 weeks after treating a dog or puppy that was treated for coccidia to help confirm that the treatment was effective.

Dogs should also be tested when symptoms of possible coccidia infection are present such as mucous diarrhea, bloody diarrhea, vomiting, lack of appetite, abdominal distress (discomfort), and weight loss. Please contact a veterinarian right away if your dog is acting sick.

Some veterinarians do the Fecal O&P at their practice with trained veterinary technicians. Most however, “refer” or ship their patient’s stool samples to an external animal reference laboratory for preparation (including centrifugation), analysis, and reporting, where the laboratory technicians and testing processes are more specialized. Routine stool testing can identify the presence of coccidia but will not typically distinguish between species of coccidia.

With the simple and convenient MySimplePetLab testing solution from home (MySimplePetLab Routine Dog Stool Test), you can directly access this same professional reference lab testing for coccidia that veterinary professionals use every day. MySimplePetLab uses reference quality stool preparation techniques and centrifugation, along with a highly trained laboratory team to maximize the likelihood of finding coccidia ‘eggs’ (oocysts) if present in the sample.


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  1. VCA Hospitals, Coccidiosis in Dogs
  2. Pets & Parasites, Coccidia – Dog Owners
  3. Companion Animal Parasite Council, Coccidia
    Companion Animal Parasite Council, Cryptosporidium
  4. PetMD, Intestinal Parasite (Coccidia) in Dogs
  5. Centers for Disease Control and Prevention, Parasites – Cystoisosporiasis (formerly known as Isosporiasis)
    Centers for Disease Control and Prevention, Parasites – Cryptosporidium (also known as “Crypto”) 
  6. Merck Veterinary Manual, Coccidiosis of Cats and Dogs

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