Coccidia infection in dogs is an intestinal disease caused by protozoan parasites that attack the lining of the digestive tract. While adult dogs often show no signs, puppies and immunocompromised dogs can become very ill. Understanding how this parasite works, its symptoms, treatment, and prevention is key to protecting your dog’s health.

What Is Coccidia Infection and How Does It Affect Dogs?

Coccidia are microscopic organisms that live in the intestines of dogs. Infection occurs when a dog ingests tiny eggs (called oocysts) from contaminated feces, soil, or water. Once inside the body, these parasites damage the intestinal lining, which can lead to diarrhea, dehydration, abdominal discomfort, and weight loss. Some adult dogs remain carriers without symptoms, but they can still pass the infection to others.

The Lifecycle of Coccidia and Its Impact on a Dog’s Digestive System

The lifecycle of coccidia begins when a dog swallows oocysts. These oocysts release parasites that invade the intestinal cells, multiply, and then burst out, destroying the cells in the process. This cycle repeats over and over, leading to significant intestinal damage. The result is poor absorption of nutrients, diarrhea, and weight loss, especially in puppies. Because the eggs are shed in the stool and survive well in the environment, coccidia spreads quickly in kennels or areas with poor sanitation.

Protozoan and Coccidial Infections in Dogs

Coccidia vs. Giardia in Dogs

Both coccidia and giardia are intestinal parasites, but they cause disease in different ways. Giardia attaches to the surface of the intestines, often causing greasy or foul-smelling stools. Coccidia multiply inside the cells of the intestine, usually resulting in watery or bloody diarrhea. While both can spread through contaminated feces and water, they require different medications for treatment.

How They Differ in Dogs

Coccidia are species-specific and the ones that affect dogs do not spread to humans or cats. Giardia, on the other hand, can sometimes infect multiple species. Coccidia generally cause more severe illness in puppies, while giardia can affect dogs of all ages. The signs, diagnostic tests, and treatments are different, so it’s important for veterinarians to distinguish between the two.

Coccidial Infections in Dogs

Common Signs and Symptoms

Dogs with coccidial infections often develop watery diarrhea that may contain blood or mucus. They may also show vomiting, loss of appetite, dehydration, and weight loss. In severe cases, puppies can become weak, anemic, or even die from the infection. Adult dogs sometimes show no symptoms but can still shed the parasite in their stool.

Why Puppies and Immunocompromised Dogs Are at Higher Risk

Puppies are especially vulnerable because their immune systems are still developing. They are also more likely to be exposed through their mother’s feces or in crowded environments such as kennels. Dogs with weak immune systems, stress, or other illnesses are also at higher risk of developing serious illness from coccidia.

Treatment for Coccidial Infection in Dogs

Effective Medications

The main treatment for coccidia infection in dogs is medication that targets the parasite. Sulfadimethoxine (Albon®) is the only FDA-approved drug and is usually given daily for one to three weeks. Toltrazuril is another effective treatment, commonly used in other countries, and often requires just one to three days of dosing. In resistant or severe cases, drugs such as ponazuril or amprolium may be prescribed. Alongside medication, supportive care like fluids and electrolytes may be necessary to prevent dehydration.

How Long Does Treatment Take?

Most dogs begin improving within a few days of starting medication, but full treatment may take anywhere from 5 to 20 days depending on the drug used and the severity of the infection. Puppies and severely ill dogs may take longer to recover. Sulfadimethoxine can sometimes cause vomiting or allergic reactions, while toltrazuril may cause mild stomach upset. Because of these risks, all treatments should be given under veterinary guidance.

Signalment of Coccidia Infection in Dogs

Factors That Increase a Dog’s Risk

The likelihood of infection increases in crowded or unsanitary environments such as shelters, kennels, or breeding facilities. Stress, poor nutrition, and exposure to contaminated feces also raise the risk. Dogs that are already sick or have weakened immune systems are much more likely to develop symptoms when exposed.

Age, Breed, and Health Conditions

Coccidia infection is most common in puppies under six months old. While no breed is especially predisposed, dogs that are stressed, ill, or immunocompromised are at higher risk of severe disease. Older dogs usually resist infection better but may still carry the parasite and pass it on to others.

Coccidial Infections in Dogs Poop

Changes in Stool Consistency and Color

One of the easiest ways to spot coccidia is by looking at your dog’s stool. Infected dogs may have watery, soft, or mucous-covered stools. In severe cases, there may be blood in the stool. Puppies often develop frequent bouts of diarrhea that can quickly lead to dehydration and weight loss.

Recognizing When to Seek Veterinary Care

If your dog has persistent diarrhea, especially if it contains blood or mucus, you should contact your veterinarian immediately. Puppies with diarrhea should always be checked promptly, as they can deteriorate quickly. Diagnosis is usually made with a fecal test that identifies the parasite’s eggs. Even if your dog’s stools look normal, testing may be recommended in multi-dog households or kennels to prevent the spread of infection.

FAQs

Can coccidia spread to humans or cats?
No, the species of coccidia that affect dogs are specific to dogs and cannot infect humans or cats.

How do dogs get coccidia?
Most dogs become infected by swallowing eggs from contaminated soil, water, food, or feces.

How is coccidiosis diagnosed?
Veterinarians usually diagnose the infection with a fecal exam that looks for parasite eggs.

Is there a vaccine for coccidia?
No, there is no vaccine. Prevention relies on good hygiene and sanitation.

How long does recovery take?
Mild cases may resolve in a few days, while severe cases, especially in puppies, may take several weeks to fully recover.

References

• Merck Veterinary Manual – Coccidiosis of Cats and Dogs
• Companion Animal Parasite Council – Coccidia Guidelines
• VCA Animal Hospitals – Coccidiosis in Dogs

Next Steps

Want to know more about safety during treatment? Read our article on Side Effects and Safety of Toltrazuril.