What are coccidia?

Coccidia are small protozoans (one-celled organisms) that multiply in the intestinal tracts of dogs and cats, most commonly in puppies and kittens less than six months of age, in adult animals whose immune system is suppressed, or in animals who are stressed in other ways (e.g., change in ownership, other disease present).

In dogs and cats, most coccidia are of the genus called Isospora. Isospora canis and I. ohioensis are the species most often encountered in dogs. Regardless of which species is present, we generally refer to the disease as coccidiosis. As a puppy ages, it tends to develop a natural immunity to the effects of coccidia. As an adult, it may carry coccidia in its intestines, shed the cyst in the feces, but experience no ill effects.

How are coccidia transmitted?

A puppy is not born with the coccidia organisms in its intestine. However, once born, the puppy is frequently exposed to its mother's feces, and if the mother is shedding the infective cysts in her feces, then the young animals will likely ingest them and coccidia will develop within their intestines. Since young puppies, usually those less than six months of age, have no immunity to coccidia, the organisms reproduce in great numbers and parasitize the young animal's intestines. Oftentimes, this has severe effects.

From exposure to the coccidia in feces to the onset of the illness is about 13 days. Most puppies who are ill from coccidia are, therefore, two weeks of age and older. Although most infections are the result of spread from the mother, this is not always the case. Any infected puppy or kitten is contagious to other puppies or kittens. In breeding facilities, shelters, animal hospitals, etc., it is wise to isolate those infected from those that are not.

What are the symptoms of coccidiosis?

The primary sign of an animal suffering with coccidiosis is diarrhea. The diarrhea may be mild to severe depending on the level of infection. Blood and mucous may be present, especially in advanced cases. Severely affected animals may also vomit, lose their appetite, become dehydrated, and in some instances, die from the disease.

Most infected puppies encountered are in the four to twelve week age group. The possibility of coccidiosis should always be considered when a loose stool or diarrhea is encountered in this age group. A microscopic fecal exam by a veterinarian will detect the cysts confirming a diagnosis.

What are the risks?

Although many cases are mild, it is not uncommon to see severe, bloody diarrhea result in dehydration and even death. This is most common in animals who are ill or infected with other parasites, bacteria, or viruses. Coccidiosis is very contagious, especially among young puppies. Entire kennels may become contaminated, with puppies of many age groups simultaneously affected.

What is the treatment of coccidiosis?

It should be mentioned that stress plays a role in the development of coccidiosis. It is not uncommon for a seemingly healthy puppy to arrive at its new home and develop diarrhea several days later leading to a diagnosis of coccidia. If the puppy has been at the new home for less than thirteen days, then it had coccidia before it arrived. Remember, the incubation period (from exposure to illness) is about thirteen days. If the puppy has been with its new owner several weeks, then the exposure to coccidia most likely occurred after the animal arrived at the new home.  Usually coccidia was present only to surface during the stressful period of the puppy adjusting to a new home.

Fortunately, coccidiosis is treatable. Drugs such as sulfadimethoxine (Albon) and trimethoprim-sulfadiazine (Tribrissen) have been effective in the treatment and prevention of coccidia. Because these drugs do not kill the organisms, but rather inhibit their reproduction capabilities, elimination of coccidia from the intestine is not rapid. By stopping the ability of the protozoa to reproduce, time is allowed for the puppy's own immunity to develop and remove the organisms. Drug treatments of five or more days are usually required.

How is coccidiosis prevented or controlled?

Because coccidia is spread by the feces of carrier animals, it is very important to practice strict sanitation. All fecal material should be removed. Housing needs to be such that food and water cannot become contaminated with feces. Clean water should be provided at all times. Most disinfectants do not work well against coccidia; incineration of the feces, and steam cleaning, immersion in boiling water or a 10% ammonia solution are the best methods to kill coccidia. Coccidia can withstand freezing.

Cockroaches and flies can mechanically carry coccidia from one place to another. Mice and other animals can ingest the coccidia and when killed and eaten by a dog, for instance, can infect the dog. Therefore, insect and rodent control are very important in preventing coccidiosis.

The coccidia species of dogs and cats do not infect humans.



Giardia are protozoa (one-celled organisms) that live in the small intestine of dogs and cats. Giardia are found throughout the United States and in many other parts of the world. Infection with Giardia is called 'giardiasis.'

There are many things we do not know about this parasite. Experts do not agree on how many species of Giardia there are and which ones affect which animals. Veterinarians do not even agree on how common Giardia infections are and when they should be treated. Generally, it is believed that infection with Giardia is common but disease is rare. There is much about the life cycle we do not know either.

How do Giardia reproduce and how are they transmitted?

A dog becomes infected by eating the cyst form of the parasite. In the small intestine, the cyst opens and releases an active form called a trophozoite. These have flagella, hair-like structures that whip back and forth allowing them to move around. They attach to the intestinal wall and reproduce by dividing in two. After an unknown number of divisions, at some stage, in an unknown location, this form develops a wall around itself (encysts) and is passed in the feces. The Giardia in the feces can contaminate the environment and water and infect other animals and people.

What are the signs of a Giardia infection?

Most infections with Giardia are asymptomatic. In the rare cases in which disease occurs, younger animals are usually affected, and the usual sign is diarrhea. The diarrhea may be acute, intermittent, or chronic. Usually the infected animals will not lose their appetite, but they may lose weight. The feces are often abnormal, being pale, having a bad odor, and appearing greasy. In the intestine, Giardia prevents proper absorption of nutrients, damages the delicate intestinal lining, and interferes with digestion.

Can Giardia of dogs infect people?

This is another unknown. There are many species of Giardia, and experts do not know if these species infect only specific hosts. Sources of some human infections have possibly been linked to beavers, other wild animals, and domestic animals. Until we know otherwise, it would be wise to consider infected animals capable of transmitting Giardia to humans.

You may have heard about Giardia outbreaks occurring in humans due to drinking contaminated water. Contamination of urban water supplies with Giardia is usually attributed to (human) sewage effluents. In rural settings, beavers most often get the blame for contaminating lakes and streams. Giardia outbreaks have also occurred in day care centers fueled by the less than optimal hygienic practices of children.

How do we diagnose giardiasis?

Giardiasis is very difficult to diagnose because the protozoa are so small and are not passed with every stool. Tests on serial stool samples (one stool sample every day for three days) are often required to find the organism. Special diagnostic procedures, beyond a routine fecal examination, are necessary to identify Giardia. The procedures we use to identify roundworms and hookworms kill the active form of Giardia and concentrate the cyst form.

To see the active form, a small amount of stool may be mixed with water on a microscope slide and examined under high magnification. Because these forms have flagella, you can see them move around on the slide. The active forms are more commonly found in loose stools. If you ever have the opportunity to see the active form of Giardia under the microscope, take it! It is an interesting looking creature. It is pear-shaped and its anatomy makes it look like a cartoon face, with eyes (which often look crossed), nose, and mouth. Once you see it, you will not forget it.

Cysts are more commonly found in firm stools. Special solutions are used to separate the cysts from the rest of the stool. The portion of the solution that would contain the cysts is then examined microscopically.

Tests which detect antigens of Giardia in the feces are becoming more available. These tests are more difficult to run, are more expensive, and their accuracy may not be better than other methods. In the future, these tests will hopefully be fine-tuned so we can more accurately diagnose infection with Giardia.

We have done the tests, now what?

Now we come to how to interpret the test results. It can be a dilemma for your veterinarian. What you see (or do not see) is not always a correct indication of what you have. A negative test may mean the animal is not infected. It may also mean there were too few Giardia present in the small portion of stool that was examined. Negative test results are common in infected animals. If a negative test occurs, your veterinarian will often suggest repeating the fecal examination at least two more times on different samples taken on different days. Repeat tests are often necessary to finally find the organism.

What about a positive test? That should not be hard to interpret, right? Wrong. Giardia can be found in many dogs with and without diarrhea. If we find Giardia, is it the cause of the diarrhea or is it just coincidence we found it? The animal could actually have diarrhea caused by a bacterial infection, and we just happened to find the Giardia. Test results always need to be interpreted in light of the signs, symptoms, and medical history.

If we find Giardia, how do we treat it?

Here we go again; treatment is controversial too. There is a question about when to treat. If Giardia is found in a dog without symptoms should we treat the animal? Since we should not know if G. canis can infect man, we often err on the side of caution and treat an asymptomatic infected animal to prevent possible transmission to people.

If we highly suspect infection with Giardia,, but can not find the organism, should we treat anyway? This is often done. Because it is often difficult to detect Giardia in the feces of dogs with diarrhea, if there are no other obvious causes of diarrhea (e.g., the dog did not get into the garbage several nights ago) we often treat the animal for giardiasis.

There are several treatments for giardiasis; some of them have not been FDA approved to treat giardiasis in dogs. Metronidazole is one of these, but is the old standby. The nice thing about this drug is that it also kills some types of bacteria that could cause diarrhea. So if the diarrhea was caused by bacteria, and not Giardia, we still kill the cause of the diarrhea and eliminate the symptoms. Makes us look pretty sharp! Unfortunately, metronidazole has some drawbacks. It has been found to be only 60-70% effective in eliminating Giardia from infected dogs. In some dogs, it can cause vomiting, anorexia, and some neurological signs. It also can be toxic to the liver in some animals. It is suspected of being a teratogen so it should not be used in pregnant animals. Finally, it has a very bitter taste and many animals resent taking it.

Quinacrine hydrochloride has been used in the past, but is not very effective and can cause side effects such as lethargy, vomiting, anorexia, and fever.

A newer drug, albendazole, has been shown to be 50 times more effective than metronidazole and 10-40 times more effective than quinacrine hydrochloride in killing Giardia in the laboratory. It has not been approved for use in dogs. Some serious side effects of albendazole have been noted, including injury to the bone marrow. Since it may also cause birth defects, it should not be used in pregnant animals.

In a recent small study, fenbendazole, which has been approved for treatment of roundworm, hookworm, and whipworm infections in dogs, has been shown to be effective in treating giardiasis in dogs. It is safe to use in puppies.

Most recently, a combination of praziquantel, pyrantel pamoate and febantel has been shown to decrease cyst excretion in infected dogs.

This table summarizes the information above.

  Dose Use in pregnant animals or puppies?


11.5 mg/lb twice daily for 5 days


Quinacrine hydrochloride


3 mg/lb twice daily for 5 days




11.5 mg/lb twice daily for 2 days




22.5 mg/lb once daily for 3 days

Safe in puppies 6 weeks or older

Praziquantel/ pyrantel pamoate/ febantel


Use manufacturer's suggested dosage



(puppies must be 3 weeks old and weigh more than 2 pounds)

But now we come to yet another unknown. It is possible these treatments only remove the cysts from the feces but do not kill all the Giardia in the intestine. This means even though the fecal exams after treatment may be negative, the organism is still present in the intestine. This is especially true of the older treatments. So treated animals could still be a source of infection for others.

How can I prevent my pet from becoming infected with Giardia?

The cysts can live several weeks to months outside the host in wet, cold environments. So lawns, parks, kennels, and other areas that may be contaminated with animal feces can be a source of infection for your pet. You should keep your pet away from areas contaminated by the feces of other animals. This is not always easy.

As with other parasites of the digestive system, prevention of the spread of Giardia centers on testing and treating infected animals and using sanitary measures to reduce or kill the organisms in the environment. Solutions of Lysol, bleach, and quaternary ammonium compounds are effective against Giardia.

How do I control Giardia in my kennel?

Infection with Giardia can be a big problem in kennels. Veterinarians at Cornell University have developed a specific protocol. They recommended a four-pronged approach.

Treat Animals: Treat all nonpregnant animals with fenbendazole or albendazole for 5 days. On the last day of treatment, move them to a holding facility while a clean area is established. When the animals are moved back to the clean area, treat them once again with a 5-day course of fenbendazole or albendazole.

Decontaminate the Environment: Establish a clean area. If possible, this can be the whole facility. Otherwise, create a few clean runs or cages, separate from the others. Remove all fecal material from the areas since the organic matter in feces can greatly decrease the effectiveness of many disinfectants. Steam clean the area and then clean it with a quaternary ammonium disinfectant according to the manufacturer's directions. These solutions will generally kill the cysts within one minute. Then let the area dry for several days before reintroducing the animals.

Clean the Animals: Cysts can remain stuck to the haircoats of infected animals. So before moving the treated animals to the clean area, they should be shampooed and rinsed well. Especially concentrate on the perianal area. The Cornell researchers then recommend washing the animals with a quaternary ammonium compound, using the manufacturers recommended dilution. Be sure all shampoo has been rinsed from the animal, as it will neutralize the effect of the quaternary ammonium compounds. Leave the compound on the animal for 3 minutes, then completely rinse the animals. These compounds can be irritating. Do not leave them on for more than 3 minutes. Do not get these compounds on mucous membranes or in the eyes. Always use an ophthalmic ointment to protect the eyes.

Prevent Reintroduction of Giardia: Giardia can be brought into the kennel either by introducing an infected animal or on your shoes or boots. Any new animal should be quarantined from the rest of the animals and be treated and cleaned as described above. You should either use disposable shoe covers or clean shoes/boots and use a footbath containing quaternary ammonium compounds to prevent people from reintroducing Giardia.

Remember, Giardia of dogs may infect people, so good, personal hygiene should be used by adults when cleaning kennels or picking up the yard, and by children who may play with pets or in potentially contaminated areas.

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