Protozoa cause several common feline diseases.  Protozoan infections can generally be diagnosed with a fecal float exam by a vet or trained technician. Some of the protozoa are harder to detect and may need special training or stains to diagnose. Here is some information on common protozoan infections:









Coccidia are parasites that are often misunderstood in cats. After the first exposure, coccidia parasites are always present in the kitten's intestines, and they're just waiting to take advantage of any digestive upset. It is rarely the initial cause of the diarrhea, but once diarrhea starts, the coccidia will overgrow to large numbers to keep the diarrhea going. Coccidia are a major issue for kittens under 8 weeks old and can even kill them.

Kittens are born with a sterile gut, and their mother seeds their gut with good bacteria during cleaning and care. However, Kittens can also get coccidia from their moms, so the goal is to keep the kitten's exposure to a minimum number. There are a variety of products you can use for both treatment and prevention, but prevention is most important for consistently healthy kittens.

Cocci Guard is an easy way to prevent coccidia - simply add it to your kitten's food. The mother should also be fed kitten food with Cocci Guard when you bring her to the birthing area 2 weeks before birth. This decreases the number of coccidia the mother can give to the litter.

Amprolium (Corid or Cocci-Rid) can also be used as coccidia prevention. The flavor is terrible, so some people add it to fish flavored food to try and help the taste, but no flavor works well.  The preferred way to use Amprolium is to dose the kitten daily - you know the dose is in and they will also drink adequate water.

Marquis is used to both prevent and treat coccidia. It works well and the once-a-week dose is easy to use. Marquis (ponazuril) will can cause dry eye, so use caution in kittens under 6 weeks old.  Marquis lasts 7 days, and when it's given before shipment, it's very effective in stopping coccidia from overwhelming the kittens as they adjust to their new home.

Sulfa drugs have long been used to treat coccidia and they're still effective prevention. However, Albon has seen some resistance from years of use. The best way to monitor resistance is to track the complaints post sale and switch your preventative before issues arise. You can switch back to Albon after 6 months or a year of using another preventative. Sulfa-Trimeth is related to Albon and has been used the last few years with excellent efficacy.

Baycox by Bayer is a product often asked about. The bad news is that this drug is not available in the United States yet, but it is available in some other countries by prescription. The active ingredient, Toltrazuril is active inside the cell where coccidia reproduce. This means Baycox kills coccidia, while most treatments just prevent coccidia from reproducing. A study on puppies showed it to be very effective for eliminating coccidia from the puppy. Off label use for kittens in Germany showed no adverse effects, and it's also effective against Toxoplasmosis. Both treatment results are exciting and I hope we see this product legally in the US soon.

Coccidia are always present in the cat, but if you can prevent them from becoming an issue, you may never need to treat coccidia again!


Coccidia are a common parasite of young puppies and kittens. They are single celled organisms that cause diarrhea as they reproduce inside intestinal cells, ultimately killing the cell inside which they divide. As their numbers increase, so does the number of intestinal cells being killed until so many cells are killed that the host animal dies from its severe bloody diarrhea or the host’s immune system wins and kills off the Coccidia. Drugs used against Coccidia can suppress reproduction of the organism and thus keep the numbers down, but only the host’s immune system can actually rid the body of the infection.

Coccidia infection is the scourge of the dairy industry, as it is one of the most common causes of calf death. Coccidia infection is similarly a nightmare for small puppies and kittens.


Generally speaking, carnivores like dogs and cats get infected with Isospora species of while livestock (goats, sheep, calves, and even rabbits) get Eimeria species and these species of Coccidia do not cross over.

Cryptosporidium are similar to Coccidia and, until recent advances in molecular biology showed us otherwise, they were believed to be simply another species of Coccidia. Cryptosporidium have some uniquely unpleasant features:

  • Cryptosporidium oocysts are so small that they are very difficult to detect under the microscope with normal testing methods.
  • Cryptosporidium from dogs and cats do not readily infect humans with the exception of immunosuppressed individuals. For these people, infection is life-threatening. (Cryptosporidium from livestock more readily infects humans, causing severe diarrhea that sometimes results in hospitalization.)
  • Because they are not truly Coccidia, drugs that would work on Coccidia do not have any effect on Cryptosporidium.
  • Out in the world Cryptosporidium oocysts (the infective stage) are very tough. They resist bleach and most other normal cleansers. Only prolonged exposure to ammonia or extreme temperatures can kill them.
  • In calves, only 10 oocysts are needed to establish a significant infection (i.e., that is how many the calf has to swallow). This is a particularly small number. We do not know how small the number is for other species.


The life cycle of this organism is rather complicated and it is probably not necessary to understand all the stages. The short version is that an oocyst (sort of like an egg) is passed in the feces of an infected animal. This oocyst is swallowed by another animal via licking dirt off its fur, drinking contaminated water or some such activity. The oocyst releases sporozoites (sort of like a spore) into the intestinal tract of the new host. The sporozoite infects an intestinal cell and divides. The spores divide into other stages with other names, which in turn infect more cells. All this cell division occurs asexually for a while until eventually the Cryptosporidium begins a sexual phase: instead of making more copies of itself by simple cell division it produces male and female cells. Fertilization occurs yielding oocysts (like the egg that started it all). There are actually two types of oocysts: one that is thick-walled and ready to be passed in feces to face the external world, and one that is thin-walled and just infects the host over again from the beginning.

This is a very important and bad thing so we will say it again: the thin-walled oocyst infects the host over again from the beginning. No contaminated water is needed. No dirty fur necessary. This is now a self-perpetuating infection.


The prevalence of Cryptosporidium oocyst shedding in dogs has varied from 2% to up to 15% to 20% in stray dog populations. Fecal specimens from 200 stray dogs impounded at the San Bernardino City and County animal shelters were screened for Cryptosporidium oocysts and (2%) of dogs were found to be oocyst positive. A similar survey of 206 cats revealed oocyst shedding in 5.4%. Most infections are subclinical, meaning that the host animal is not sick.

Humans tend to get their own species of Cryptosporidium (Cryptosporidium hominis) while cats and dogs each have their own Cryptosporidium. Pet ownership has not been found to be a significant risk for humans with cryptosporidiosis (i.e. most infected humans get infected from other humans or from livestock).

This is generally good news except for the immunosuppressed owner, who might adopt an infected pet without knowing it. Remember, in the immunosuppressed individual Cryptosporidiosis can be a life-threatening infection.


A routine fecal flotation test, as is recommended annually for most pets, is likely to miss Cryptosporidium as it is such a small organism. The good news is that an ELISA test kit is available that can detect all species of Cryptosporidium and can be easily run by most veterinary laboratories. Detecting Cryptosporidium is not a problem if one thinks to look for it. PCR testing, a very sensitive type of test that looks for a target organism's DNA, is also available.


The bad news is that treatment is difficult. Nothing can really be described as highly effective. A medication called Paromomycin has been effective but is highly toxic to the kidneys. A medication called Nitazoxanide has been effective but causes nausea and diarrhea. Clindamycin in combination with Tylosin is currently favored.



Kittens and cats living in groups have an assortment of infectious diseases to contend with: upper respiratory infections, coronavirus, coccidia, to name a few. Tritrichomonas foetus is yet another infectious organism yielding diarrhea in feline patients, usually with a history of group lifestyle. This organism was previously thought to infect only cattle where it causes miscarriage and fertility problems, but recently (in 2003) T. foetus has emerged as an infectious agent for cats. Information and recommendations regarding this organism have changed in the last several years and we attempt to provide the most up to date summary of what is known and recommended for prevention and treatment of this infection.


The short answer is that this is a single-celled organism. The longer version is that this is a flagellate, a single-celled organism possessing lash-like structures, called “flagella,” on its “body” which wave around allowing the organism to move. T. foetus is commonly mistaken for Giardia, another parasitic flagellate as they both use flagella to move around and both have pear shaped bodies.


T. foetus organisms are shed in the feces of an infected cat. Most commonly, transmission occurs when cats share a litter box as the organism can live up to 3 days in fecal material. Any time a cat steps in the feces of an infected cat, organisms can be transferred to the paws and later licked up during grooming.


T. foetus colonizes the lower intestine of the cat causing the mucous and sometimes bloody diarrhea that characterizes colitis. If the colon is biopsied, inflammatory cell infiltration typical of inflammatory bowel disease will be seen. Infected cats do not always have diarrhea; many cats especially older ones have no symptoms at all but are still contagious to other cats.

Because colitis can have so many causes, it is important to keep this possible cause in mind. Chronic colitis may or may not respond to symptomatic treatment and if a specific underlying cause can be identified and treated, a long-term difficult problem can be potentially resolved permanently. Many colitis remedies will lead to temporary improvement for a Tritrichomonas-infected cat but the symptoms generally come right back after treatment ceases.


There are presently four testing methods that can be used to identify Tritrichomonas foetus in a fecal sample. It should be noted that a proper fecal sample for testing must be freshly voided (i.e. immediately retrieved from the anus with no cat litter contamination), obtained with a deeply inserted fecal loop, or flushed from the colon with a syringe. Bringing a sample from home will not be adequate. If the cat has been on antibiotics, this will interfere with testing; the cat should be off antibiotics for at least a couple of days.

Direct Smear
Here some fecal matter is swabbed onto a microscope slide, mixed with a gentle saline solution, and examined for the presence of flagellate organisms. The feces must be immediately fresh from the rectum. The wetter and more mucous the sample, the better. Usually several slides must be examined as the organism is elusive. Standard fecal tests for parasites will not pick up this organism. Refrigeration of the sample will kill the organism and make it impossible to detect. Further, if the patient is on antibiotics the number of organisms available to detect will be greatly reduced even though most antibiotics cannot cure the infection.

While this is a relatively easy test to perform, it only has about a 14% chance of detecting a natural T. foetus infection. A more sensitive test is generally preferred.

Culture (also called the “Pouch Test”)

A special culture bag can be used to grow T. foetus in numbers large enough for detection. The feces used must be freshly obtained from the rectum, inoculated into the pouch, and the pouch is kept in a vertical position for 12 days at room temperature. The pouch is periodically examined under the microscope for the presence of organisms.

This is the test method of choice in most cases as it is easy to perform, reasonably priced and generally accurate.

PCR Testing (Polymerase Chain Reaction Testing)

PCR testing is a DNA test for the presence of T. foetus. A larger fecal sample is needed and the test must be done at a reference lab. It is generally reserved for patients where the Pouch test has been negative but the index of suspicion is still high.

PCR testing is the most sensitive of all the test methods but is also fairly expensive. Specialized equipment is needed and only a few laboratories are qualified to run samples.


A routine colon biopsy is unlikely to find this parasite; special stains on the tissue (“immunohistochemistry”) must be requested and at least six tissue samples must be examined. This is the most invasive form of testing and would not be done right off the bat but if the patient is going to have a biopsy for chronic colitis anyway, it might be a good idea to have the pathologist look for T. foetus.

A negative test never rules out Tritrichomonas infection
no matter which test is performed.


In the past several different antibiotics have been reported to be effective but it turns out that this is probably an overestimate since 88% of cats will resolve their diarrhea spontaneously within 2 years. They will still be infected, or at least 57% of them will, but will have normal stool and they may relapse with stress.

  • One treatment option is to simply wait for resolution if the household does not have a large number of cats and the diarrhea is not excessive.

The only drug that is felt to be reliable against T. foetus is ronidazole, and its use is far from straight-forward. Here is what to know:

  • Ronidazole must be compounded to get a dose in a suitable size for cats.
  • Ronidazole is not licensed for use in cats; it is a poultry antibiotic. It also tastes very bad and should be provided in capsules rather than as an oral liquid so as to avoid the taste.
  • The owner must wear gloves when handling ronidazole.
  • The most common side effect in cats is neurotoxicity which means it is not appropriate to use ronidazole as a trial to see if a cat with colitis improves on it. Ronidazole should be used only in confirmed Tritrichomonas patients.
  • Neurotoxicity manifests as loss of appetite, incoordination, and possibly seizures. Some experts recommend engaging the cat in play on a daily basis to assess muscular coordination and agility.
  • Cats being treated should be isolated from other cats in the home to prevent reinfection.
  • It is not possible to fully confirm that an infection has been eradicated as a negative PCR test does not rule out infection. Experts recommend a PCR test in 1-2 weeks after treatment and again 20 weeks after treatment as the closest we can come to confirming eradication.
  • Ronidazole is usually given once daily for two weeks. The diarrhea should be resolved by the end of this course



Campylobacteriosis is an infectious diarrheal disease that's found in both animals and people. Campylobacter can be found in 20 to 30% of dogs or cats with diarrhea, and 10% of the normal dogs or cats in an infected cattery, kennel or humane/rescue kennel. It's also referred to as "Show Crud" since it's very common in show dogs.

Transmission to Neonates:
The most common ways campylobacteriosis is transmitted is through eating infected feces and through contaminated food and water. The bacteria are shed in the feces of infected and asymptomatic carriers - many chicken flocks and birds are infected but show no signs of illness. It can also easily be spread through an infected water source or raw meats, especially chicken. Puppies or kittens under six months of age are the most susceptible. Dogs and cats over 6 months are quite resistant to diarrhea, but they may become asymptomatic carriers, which keeps the organism in the cattery or kennel.

Clinical Picture:
Neonates often break with the disease in the weaning period or shortly after arriving at a rescue kennel. Clinical signs vary from mild to severe, depending on the stress level of the neonate - you may see loose feces, watery diarrhea or bloody mucoid diarrhea. Unlike many viral infections, puppies and kittens generally do not have a fever, vomit or lose their appetite. This helps you distinguish Campylobacter from Parvovirus.

In humans, severe abdominal discomfort, diarrhea with severe vomiting and fever can last up to one week. It is often mistaken for appendicitis. Campylobacter is one of the most common causes of diarrheal illness in the United States. The best prevention is hand washing with soap and water. Some studies have even shown soap to be superior to antibacterial products, which means mechanical washing is important!

There are many different treatments available that have shown varying amounts of success. You should talk to your veterinarian to find the best option for your dogs. You need to keep them on the medication for a minimum of 21 days to clear Campylobacter - we don't want to create carriers by stopping treatment too early. In addition to treatment, electrolytes are especially important with any diarrhea to prevent dehydration.

  • Antibiotics such as azithromycin (Zithromax) or erythromycin can shorten the duration of symptoms if it's given early in the illness. Azithromycin (Zithromax) 5 mg/lb daily for 5 days then every 5 days for three treatments. Erythromycin is currently unavailable.
  • Cephalexin at 15 mg/lb twice daily has also been used successfully.
  • Tylan at 10mg/lb given twice a day can be given orally or mixed in the water, using it as the only water source. You need to keep them on the medication for a minimum of 21 days to clear Campylobacter - we don't want to create carriers by stopping treatment too early.
  • Doxycycline/tetracycline is easy to get and use. Tetracycline cannot be uses in neonates of any species because it stains teeth that have not erupted yet. Doxycycline is safe for neonates - give at 5 mg/lb for three weeks. It's also often used with Tylan in the water. Since Doxy is inactive in the lower intestine, we may get much of that effect from Tylan. You shouldn't use Doxycycline alone.



What is toxoplasmosis?

Toxoplasmosis is a disease caused by a single-celled parasite called Toxoplasma gondii (T. gondii). Toxoplasmosis is one of the most common parasitic diseases and has been found in nearly all warm-blooded animals, including pets and humans. Despite the high prevalence of T. gondii infection, the parasite rarely causes significant clinical disease in cats-or any species.

What causes toxoplasmosis?

The life cycle of Toxoplasma gondii is complex and involves two types of host-definitive and intermediate. Cats, both wild and domestic, are the only definitive hosts for Toxoplasma gondii. This means that the parasite can only produce oocysts (eggs) when infecting a cat. When a cat ingests an infected prey (or other infected raw meat) the parasite is released into the cat's digestive tract. The organisms then multiply in the wall of the small intestine and produce oocysts during what is known as the intraintestinal infection cycle. These oocysts are then excreted in great numbers in the cat's feces. Cats previously unexposed to T. gondii will usually begin shedding oocysts between three and 10 days after ingestion of infected tissue, and continue shedding for around 10 to 14 days, during which time many millions of oocysts may be produced. Oocysts are very resistant and may survive in the environment for well over a year.

During the intraintestinal infection cycle in the cat, some T. gondii organisms released from the ingested cysts penetrate more deeply into the wall of the intestine and multiply as tachyzoite forms. These forms then spread out from the intestine to other parts of the cat's body, starting the extraintestinal infection cycle. Eventually, the cat's immune system restrains this stage of the organism, which then enters a dormant or "resting" stage by forming cysts in muscles and brain. These cysts contain bradyzoites, or slowly multiplying organisms.

Other animals, including humans, are intermediate hosts of Toxoplasma gondii. These hosts can become infected but do not produce oocysts. Oocysts passed in a cat's feces are not immediately infectious to other animals. They must first go through a process called sporulation, which takes one to five days depending on environmental conditions. Once sporulated, oocysts are infectious to cats, people, and other intermediate hosts. Intermediate hosts become infected through ingestion of sporulated oocysts, and this infection results in formation of tissue cysts in various tissues of the body. Tissue cysts remain in the intermediate host for life and are infectious to cats, people and other intermediate hosts if the cyst-containing tissue is eaten.

How will toxoplasmosis affect my cat?

Most cats infected with T. gondii will not show any symptoms. Occasionally, however, clinical disease-toxoplasmosis-occurs. When disease does occur, it may develop when the cat's immune response is not adequate to stop the spread of tachyzoite forms. The disease is more likely to occur in cats with suppressed immune systems, including young kittens and cats with feline leukemia virus (FELV) or feline immunodeficiency virus (FIV).

The most common symptoms of toxoplasmosis include fever, loss of appetite, and lethargy. Other symptoms may occur depending on whether the infection is acute or chronic, and where the parasite is found in the body. In the lungs, T. gondii infection can lead to pneumonia, which will cause respiratory distress of gradually increasing severity. Toxoplasmosis can also affect the eyes and central nervous system, producing inflammation of the retina or anterior ocular chamber, abnormal pupil size and responsiveness to light, blindness, incoordination, heightened sensitivity to touch, personality changes, circling, head pressing, twitching of the ears, difficulty in chewing and swallowing food, seizures, and loss of control over urination and defecation.

How is toxoplasmosis diagnosed in cats?

Toxoplasmosis is usually diagnosed based on the history, signs of illness, and the results of supportive laboratory tests. Measurement of IgG and IgM antibodies to Toxoplasma gondii in the blood can help diagnose toxoplasmosis. The presence of significant IgG antibodies to T. gondii in a healthy cat suggests that the cat has been previously infected and now is most likely immune and not excreting oocysts. The presence of significant IgM antibodies to T. gondii, however, suggests an active infection of the cat. The absence of T. gondii antibodies of both types in a healthy cat suggests that the cat is susceptible to infection and thus would shed oocysts for one to two weeks following infection.

Sometimes the oocysts can be found in the feces, but this is not a reliable method of diagnosis because they look similar to some other parasites. Also, cats shed the oocysts for only a short period of time and often are not shedding the oocysts when they are showing signs of disease. A definitive diagnosis requires microscopic examination of tissues or tissue impression smears for distinctive pathologic changes and the presence of tachyzoites.

Can toxoplasmosis be treated?

Most cats that have toxoplasmosis can recover with treatment. Treatment usually involves a course of an antibiotic called Clindamycin. Other drugs that are used include pyrimethamine and sulfadiazine, which act together to inhibit T. gondii reproduction. Treatment must be started as soon as possible after diagnosis and continued for several days after signs have disappeared. In acute illness, treatment is sometimes started on the basis of a high antibody titer in the first test. If clinical improvement is not seen within two to three days, the diagnosis of toxoplasmosis should be questioned.

No vaccine is as yet available to prevent either T. gondii infection or toxoplasmosis in cats, humans, or other species.

Can I "catch" toxoplasmosis from my cat?

Because cats only shed the organism for a few days in their entire life, the chance of human exposure is small. Owning a cat does not mean you will be infected with the disease. It is unlikely that you would be exposed to the parasite by touching an infected cat, because cats usually do not carry the parasite on their fur. It is also unlikely that you can become infected through cat bites or scratches. In addition, cats kept indoors that do not hunt prey or are not fed raw meat are not likely to be infected with T. gondii.

In the United States, people are much more likely to become infected through eating raw meat and unwashed fruits and vegetables than from handling cat feces.

How are people infected with Toxoplasma gondii?

Contact with oocyst-contaminated soil is probably the major means by which many different species-rodents, ground-feeding birds, sheep, goats, pigs, and cattle, as well as humans living in developing countries-are exposed to Toxoplasma gondii. In the industrialized nations, most transmission to humans is probably due to eating undercooked infected meat, particularly lamb and pork. People also become infected by eating unwashed fruits and vegetables. The organism can sometimes be present in some unpasteurized dairy products, such as goat's milk. Toxoplasma gondii can also be transmitted directly from pregnant woman to unborn child when the mother becomes infected during pregnancy.

There are two populations at high risk for infection with Toxoplasma gondii; pregnant women and immunodeficient individuals. Congenital infection is of greatest concern in humans. About one-third to one-half of human infants born to mothers who have acquired Toxoplasma during that pregnancy are infected. The vast majority of women infected during pregnancy have no symptoms of the infection themselves. The majority of infected infants will show no symptoms of toxoplasmosis at birth, but many are likely to develop signs of infection later in life. Loss of vision, mental retardation, loss of hearing, and death in severe cases, are the symptoms of toxoplasmosis in congenitally infected children.

In immunodeficient people-those undergoing immunosuppressive therapy (e.g., for cancer or organ transplantation) or those with an immunosuppressive disease such as AIDS-enlargement of the lymph nodes, ocular and central nervous-system disturbances, respiratory disease, and heart disease are among the more characteristic symptoms. In these patients-especially those with AIDS-relapses of the disease are common, and the mortality rate is high. In the past, immunodeficient people and pregnant women were advised to avoid cats. However, the Centers for Disease Control (CDC) now advises that this is not necessary.

What can I do to prevent toxoplasmosis?

There are several general sanitation and food safety steps you can take to reduce your chances of becoming infected with Toxoplasma:

  • Do not eat raw or undercooked meat. Meat should be cooked to a temperature of at least 160°F for 20 minutes.
  • Do not drink unpasteurized milk.
  • Do not eat unwashed fruits and vegetables.
  • Wash hands and food preparation surfaces with warm soapy water after handling raw meat.
  • Wear gloves when gardening. Wash hands after gardening.
  • Wash hands before eating (especially for children).
  • Keep children's sandboxes covered.
  • Do not drink water from the environment unless it is boiled.
  • Do not feed raw meat or undercooked meat to cats. Also, do not give them unpasteurized milk.
  • Do not allow cats to hunt or roam.
  • Do not allow cats to use a garden or children's play area as their litter box.
  • Remove feces from the litter box daily and clean with boiling or scalding water.
  • Pregnant women, and persons with suppressed immune systems, should not clean the litter box.
  • Control rodent populations and other potential intermediate hosts.



Giardia is the genus of a protozoan parasite infectious to both humans and pets all over the world. Giardia are flagellates, which mean they move by means of several whip-like structures called “flagella.” They live as a form called a “trophozoite” or “troph” for short, in the intestine where it causes diarrhea. In fresh fecal sample, trophozoites can sometimes be captured. They swim around in a jerky fashion characteristic of flagellates and appear as a funny face (see picture below – the 2 nuclei form the eyes and median bodies form the mouth).

After a short period of time outside the host’s intestine, the trophozoites round up and form cysts which enable them to survive environmental conditions without a host to protect them. The cyst can be dried out to decontaminate the environment but if it is cold and wet, the cyst can live for many months with two incompletely formed trophozoites inside, ready to infect a new host. Contaminated water is the classical source of a Giardia infection.

After they have been swallowed, the cyst shell is digested away freeing the two trophozoites who go and attach on the intestinal lining. The troph has a structure called a “ventral disc” which is sort of like a suction cup and this is used to stay attached to the intestine. If the troph wants to move to another spot, it lifts itself up and swims to a new spot via its flagella (trophs tend to live in different intestinal areas in different host species and depending the host’s diet). If the host has diarrhea, trophs are shed in the diarrhea but Giardia may also form cysts within the host in preparation to be shed. Either form can be found in fresh stool.

After infection, it takes 5-12 days in dogs or 5-16 days in cats for Giardia to be found in the host’s stool. Diarrhea can precede the shedding of the Giardia. Infection is more common in kennel situations where animals are housed in groups.


No one is completely sure but infection seems to cause problems with normal intestinal absorption of vitamins and other nutrients. Diarrhea is generally not bloody. Immune suppressive medications such as corticosteroids can re-activate an old Giardia infection.


In the past, diagnosis was very difficult. The stool sample being examined needed to be fresh plus Giardia rarely show up on the usual fecal flotation testing methods used to detect other parasites. Traditionally, a fecal sample is mixed in a salt or sugar solution such that any parasite eggs present will float to the top over 10-15 minutes. Some tricks that have been used to facilitate finding Giardia have included:

  • Being sure to examine a direct smear of the fecal sample (in hope of finding swimming trophs)
  • Floating the sample in Zinc Sulfate, a solution which has been found superior in getting Giardia cysts to float.
  • Staining the sample with some sort of iodine under the microscope to make the Giardia show up easier.

What has made Giardia testing infinitely easier is the development of a commercial ELISA test kit (similar in format to home pregnancy test kits). A fecal sample is tested immunologically for Giardia proteins. This method has dramatically improved the ability to detect Giardia infections and the test can be completed in just a few minutes while the owner waits.

Giardia shed organisms intermittently and may be difficult to detect. Sometimes pets must be retested in order to find an infection.


A broad spectrum dewormer called fenbendazole (Panacur®) seems to be the most reliable treatment at this time. Metronidazole (Flagyl®) in relatively high doses has been a classical treatment for Giardia but studies show it to only be effective in 67% of cases. The high doses required to treat Giardia also have been known to result in temporary neurologic side effects or upset stomach. For some resistant cases, both medications are used concurrently. The ELISA test for Giardia should go negative within 2 weeks of treatment indicating success.

Because cysts can stick to the fur of the infected patient and be a source for re-infection, the positive animal should receive a bath at least once in the course of treatment.

Not all patients with Giardia actually have diarrhea but because Giardia is the most common intestinal parasite affecting humans in North America, treatment is generally recommended for the pet testing positive even if no symptoms are being shown. The idea is to reduce human exposure.


A Giardia vaccine made by Fort Dodge Animal Health is on the market but not to prevent infection in the vaccinated animal. Instead the vaccine is licensed as an adjunct to treatment and is used to reduce the shedding of cysts by the vaccinated patient. This would be helpful in a kennel situation that is trying to reduce environmental contamination during an outbreak or where an animal keeps getting reinfected but is not helpful to the average dog whose owner wants to simply prevent infection.

The 2006 American Animal Hospital Association Guidelines list this vaccine as “not recommended.”


The most readily available effective disinfectant is probably bleach diluted 1:32 in water which required less than one minute of contact to kill Giardia cysts in one study. Organic matter such as dirt or stool is protective to the cyst so on a concrete surface basic cleaning should be effected prior to disinfection. Animals should be thoroughly bathed before being reintroduced into a “clean” area. A properly chlorinated swimming pool should not be able to become contaminated. As for areas with lawn or plants, decontamination will not be possible without killing the plants and allowing the area to dry out in direct sunlight