Coccidiosis is a common parasitic disease in dogs, especially in puppies and animals living in groups. Caused by intestinal protozoa of the genus Cystoisospora, it can sometimes go unnoticed, but it may also lead to severe digestive problems and even become life-threatening in the most vulnerable dogs. How is it transmitted? What symptoms should you watch for? And most importantly, how can it be prevented and treated effectively?
The key points
- Coccidiosis is a digestive parasitic disease caused by protozoa.
- It commonly affects puppies, in whom it can cause serious digestive illness, while adults are often asymptomatic.
- Standard dewormers do not work against coccidiosis.
What is coccidiosis in dogs?
Coccidiosis is a parasitic disease of the digestive system caused by protozoa of the genus Cystoisospora (formerly Isospora). These microscopic parasites mainly infect the dog’s small intestine.
After being swallowed, they multiply inside intestinal cells and destroy them. This damage leads to digestive symptoms that can range from mild to severe depending on the dog’s age, general health, and immune status.
In puppies or immunocompromised dogs, the symptoms may be pronounced. By contrast, some adult dogs carry the parasite without showing any signs, while still shedding oocysts in their stool and contaminating the environment.
For that reason, coccidiosis is often an opportunistic disease: it can remain unnoticed for a while, but become serious in certain situations.
How is coccidiosis transmitted?
Coccidiosis spreads mainly by the fecal-oral route, meaning through ingestion of oocysts, the parasite’s resistant form, present in the feces of an infected animal.
Once released into the environment, these oocysts become infectious after a few days. Dogs become infected by licking or eating contaminated surfaces, objects, floors, or food.
Close living conditions such as kennels, shelters, and breeding facilities, together with poor hygiene, greatly increase the risk of transmission. Puppies are especially exposed because their immune system is still immature and they explore their surroundings with their mouths. Mothers can also indirectly expose their litters if they are carrying coccidia. Once in the intestine, the oocysts release mobile forms that invade intestinal cells, multiply, and are shed again in the stool, completing the life cycle. There is no direct transplacental transmission or transmission through milk, unlike with some other parasites such as Toxocara.
| In Spain, several studies have reported prevalence rates ranging from 0.6% to 10.2%, with higher infection levels in dogs living in groups and in poor hygienic conditions. |
Is this disease contagious to humans?
Canine coccidiosis caused by Cystoisospora is not considered a zoonosis, meaning it is not transmitted to humans.
The coccidia species that infect dogs are host-specific. In other words, Cystoisospora canis or C. ohioensis cannot develop in humans. There is therefore no direct risk for owners or children who come into contact with an infected dog. Even so, good hygiene is always recommended, including prompt stool removal and handwashing after handling a sick animal or cleaning its environment, especially in households with young children, elderly people, or immunocompromised individuals. Other coccidia are pathogenic to humans, such as Cryptosporidium or Cyclospora, but they are not transmitted by dogs. In short, while canine coccidiosis is contagious between dogs, it does not pose a danger to humans.
What are the signs of coccidiosis in dogs?
The signs vary depending on the dog’s age, general condition, and the intensity of the infestation. Puppies are the most vulnerable. The most common signs include:
- Diarrhea: often soft to watery, sometimes greenish or mixed with mucus.
- Bloody diarrhea: blood may appear in the stool in severe cases.
- Abdominal pain: the dog may hunch its back or react when the belly is touched.
- Loss of appetite (anorexia): the dog refuses food or eats less than usual.
- Weight loss: especially noticeable in puppies, even when appetite is partly preserved.
- Fatigue and lethargy: the dog seems quieter and sleeps more.
- Stunted growth: in puppies with chronic infection.
- Vomiting: less common, but possible.
- Dehydration: when significant diarrhea is not adequately compensated.
Without treatment, the condition can become serious in young dogs.
Canine giardiasis and coccidiosis are both digestive diseases in dogs. They share some similarities, but they are also quite different:
| Criterion | Giardiasis | Coccidiosis |
|---|---|---|
| Responsible agent | Giardia duodenalis (flagellated protozoan) | Cystoisospora canis, C. ohioensis (protozoa) |
| Mode of transmission | Fecal-oral route (contaminated water, food, or objects) | Fecal-oral route (contaminated stool, environment) |
| Most affected age | Mainly puppies, but possible at any age | Mainly puppies |
| Clinical signs | Chronic or intermittent diarrhea Soft, pasty, sometimes foul-smelling stools Bloating, gas |
Acute, sometimes bloody diarrhea Abdominal pain Anorexia, weight loss, stunted growth |
| Course | Chronic, recurrent | Acute to subacute, sometimes chronic in puppies |
| Diagnosis | Specific fecal exam or ELISA/antigen test | Fecal exam (oocysts detected in stool) |
| Treatment | Metronidazole or fenbendazole | Sulfonamides (sulfadimethoxine) or toltrazuril |
| Human infectivity | Possible zoonosis for some strains | Not transmissible to humans |
Veterinary note: Giardiasis and coccidiosis are difficult to tell apart, and only a veterinary examination can confirm the diagnosis. The costs of tests and treatment for digestive disorders may be covered by dog health insurance.
What test is used to diagnose coccidiosis in dogs?
Diagnosis is based mainly on a stool analysis called coproscopy.
This test looks for oocysts under a microscope in the feces. The most commonly used method is flotation, which concentrates the oocysts so they are easier to see. It is a simple, inexpensive test that can be performed in a veterinary clinic.
However, oocyst shedding can be intermittent, which may lead to false-negative results. For that reason, it is sometimes necessary to repeat the test over several days or analyze stool collected over a 3-day period. Unlike other parasites such as Giardia, there is no commonly used rapid antigen test specifically for canine coccidia. If clinical suspicion is strong, treatment may be started even when the test is negative.
What dewormer works against coccidiosis in dogs?
Canine coccidiosis does not respond to standard dewormers used against intestinal worms such as roundworms or hookworms.
To treat this parasitic infection, dogs need protozoa-specific antiparasitic medications given by mouth.
These treatments work by blocking coccidia from multiplying in the intestine, which helps control the infection and relieve symptoms. They are generally given for 5 to 10 days, depending on how severe the clinical signs are.
Such treatments must be prescribed by a veterinarian after confirmation or strong suspicion of coccidiosis. Supportive care, including rehydration, correction of deficiencies, and an appropriate diet, may also be necessary in weakened animals.
At the same time, hygiene measures should be implemented alongside treatment:
- Remove feces immediately: infectious oocysts are present in the stool, so waste should be eliminated quickly to limit spread.
- Clean and disinfect regularly floors, bowls, kennels, cages, litter boxes, and any contaminated area with a disinfectant effective against oocysts (for example, diluted ammonia or steam above 60°C).
- Change bedding or blankets every day and wash them at high temperature (>60°C).
- Isolate sick animals from others, especially in breeding facilities or group settings, to prevent transmission.
- Wash hands thoroughly after handling a sick dog or cleaning its belongings.
- Avoid wet or contaminated areas during walks.
How long does it take to get rid of coccidia in dogs?
The time needed to eliminate coccidia depends on several factors: the severity of the infestation, the dog’s age and health status, and the medication used.
In general, antiparasitic treatment lasts between 5 and 10 days, and symptoms often improve within 48 to 72 hours. However, complete elimination of oocysts from the stool may take several days to several weeks. It is therefore advisable to continue hygiene measures even after treatment ends to avoid reinfection.
In puppies with diarrhea or in severe cases, a second treatment may be needed. A follow-up fecal exam can also be useful after treatment to make sure the parasites are gone. Thorough environmental disinfection is essential, because oocysts are resilient and can survive for several weeks in moist conditions.
Prevention is based primarily on strict hygiene in the dog’s environment, since oocysts can survive outside the body for a long time. The main measures are:
- Clean up feces daily to limit soil contamination.
- Disinfect surfaces such as kennels, bedding, and bowls with products effective against oocysts, such as ammonia or high-temperature steam.
- Avoid overcrowding in breeding facilities, shelters, or boarding facilities.
- Separate puppies from sick or carrier animals.
- Deworm puppies regularly with appropriate antiparasitic treatments when needed, depending on the situation.
- Watch for digestive signs such as diarrhea or loss of appetite and seek veterinary advice promptly if in doubt.
- Consider preventive or curative treatment for puppies raised in group settings.
Good hygiene, combined with regular veterinary follow-up, can significantly reduce the risk of coccidiosis appearing and spreading.
Coccidiosis is a common digestive parasitic disease in puppies, but it can also affect adult dogs. While it is often mild, it can cause serious digestive problems, especially in young or weakened animals.
Source:
- Muñoz, A., Morchón, R., & Montoya, A. (2018). Estudio epidemiológico de la prevalencia de coccidiosis en perros en diferentes entornos en España. Revista Española de Parasitología, 34(2), 45-52.