Giardia in Cats – Symptoms, Diagnosis and Treatment

    We see giardia in cats more often than in other pets. Giardia can be treated, but you cannot get rid of it fully. The symptoms of giardia are the same as any intestinal disease but fret not! It can be treated and diagnosed by a veterinarian. Giardia in cats often gets cured, but it can be difficult for your pet to recover from the underlying condition.

    A disorder of the small intestine caused by single-celled organisms gives rise to giardia in cats. The nature of the disease varies, but they can cause some severe problems in cats, including symptoms such as diarrhea, depression, and dehydration.

    Giardiasis is a disease of the human intestine in animals caused by the micro-parasite Giardia duodenalis (also known as G. intestinalis or G. lamblia). Giardia is a simple unicellular parasite. It is not a “worm,” a virus, or a bacteria. Among the seven genotypes, A to G, dogs usually carry C and D, cats carry F, and humans carry A and B, and E and F are not commonly reported. Giardia is found all over the world and causes “Traveller’s Diarrhoea” in humans.

    While drinking infected water, environmentalists or nature wanderers might unconsciously get “beaver fever,” which is another name for giardia in humans. Some other bacteria causing this type of intestinal infection are coccidia, cryptosporidia, and toxoplasmas.

    The parasitic organism of giardia establishes two forms: A plant form having a delicate, consuming nature is found in the intestines of the infected animals. Another form with a hard cyst is excreted along with feces. This can live up to months, feeding on the animal with giardia, especially in the humid and marshy areas.

    Amongst other symptoms of giardia in cats and humans, diarrhea is the most common. However, many cats can get sick without showing any significant symptoms, and that’s when it is considered “non-specific.” Giardia in cats can be less commonly diagnosed than its occurrence.

    How are cats infected with Giardia?

    giardia in cats

    Giardia in cats arises after ingesting the cystic stage of the parasite. After entering the cat’s intestine, the cyst forms a “trophic form” or organism. It attaches itself to the intestinal wall for ingestion. With sufficient presence, clinical signs of intestinal wall damage appear. These plant forms multiply by mitosis, and some become cystic.

    Finally, the cat guides the parasitic organisms through its feces. It takes 5 to 12 days for dogs and 5 to 16 days for cats to pass the cyst in their stools. These cysts can quickly infect other animals. Giardia in cats can be transmitted by eating or inhaling the cysts in contaminated soil or drinking contaminated water.

    Giardia in cats is more common in young ones than in healthy adult cats. The risk of this disease increases when there are many cysts in the environment due to fecal contamination. The disease is common in overcrowded cat populations, majorly among young kittens and adult cats in litter bins, pet stores, and shelters. Studies have shown that young cats excrete more giardia cysts and are more prone to giardia than aged cats.

    Transmission and life cycle of giardia in cats

    Giardiasis in Cats | Today's Veterinary Nurse

    Giardia in cats spreads through the feces and mouth. Cysts are excreted in the feces and spread after a bowel movement. These cysts can be eaten from an infected host from contaminated food or water or directly from a contaminated area in the environment.

    The cysts of giardia in cats have two types of plant forms that appear when the cyst reaches the small intestine. These plant forms are pathogenic parasites. They grow along longitudinal fissures, existing in the lumen or adhering to the mucous membrane through the abdominal suction disk, causing malabsorption and steatorrhea.

    As the plant form passes through the colon, it sweeps through the cyst to form a new cyst. The cysts are resistant to the environment and are excreted with the feces. They can be transmitted by diarrhea, but they are mostly non-contagious and unsuitable for the environment.

    Giardia in cats has a gestation period of 5 to 16 days, and the cyst sheds in a cycle. Also, you must make sure that while grooming, your cats or other pets are kept out of reach from their fur. This is because sometimes, the pets eat up their fur. If it happens to be contaminated, they might ingest the cysts and form giardia.

    What are the clinical signs of giardiasis?

    Toxoplasmosis in Cats | PetMD

    Giardia in cats happens when thin microscopic parasites attack the intestinal wall and destroy it, causing severe, sudden, pungent-smelling diarrhea. Giardia in cats can cause weight loss, acute diarrhea, and thick stools. Stools are soft and watery, often green and sometimes having blood in them. Cats with this condition have a lot of mucus in their feces. In some cases, vomiting may occur.

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    Symptoms may last for several weeks, and you may see gradual weight loss. Diarrhea may be sporadic. Giardia in cats does not usually cause fever, but it makes the body lethargic. It usually does not risk lives, but it is more severe in young cats or cats whose immune system has been destroyed by an infection such as feline immunodeficiency virus (FIV) or feline leukemia virus (FELV) other severe infection.

    Most cats and dogs do not show any symptoms and are asymptomatic carriers whereas, younger ones reveal many clinical signs.

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    What is the treatment for giardiasis?

    GI parasites — Kitten Lady

    Fenbendazole and metronidazole are the most common medications used to treat giardia in cats. Although it is mostly prepared in tablet form to alleviate the bitter taste, you would have to break it and bring out the bitter contents to get the right dose for your cat. To facilitate the administration of these drugs, you can use combined veterinary drugs to create flavored formulations to mask the bitter taste. Oral treatment lasts 5-7 days.

    You can use Fenbendazole and metronidazole both separately or in combination. Cats with refractory diarrhea (untreatable diarrhea) are usually given these two medications together. Severe dehydration and diarrhea may require supportive care with other adjuvants.

    However, you should not treat asymptomatic giardia in cats with metronidazole or fenbendazole. It can develop an anti-resistance towards other kinds of bacteria and parasites.

    The very common treatment for giardia in cats is usually imidazole (Fenbendazole), given at a dose of 50 mg/kg for 5-7 days. Fenbendazole can be used in pregnant cats.

    An alternative is Metronidazole, and it is mostly suggested to use it at a dose of 50 mg/kg for 5 days. Still, you should not use it in pregnant cats. This dose is associated with an increased risk of side effects, such as infusing toxicity in the central nervous system, causing weakness, ataxia, confusion, and seizures. More recently, it has been suggested that a daily dose of 25 mg/kg is effective and less likely to cause side effects.

    Severe cases involving cats with multiple conditions may require a second treatment. In this case, you may need a combination of fenbendazole and metronidazole. However, it has been suggested that the second course of fenbendazole treatment may induce antibiotic resistance against E. coli.

    Another approach is to use ronidazole, which is effective against giardiasis in both dogs and cats. Besides giardia in cats, it is also used to treat trichomonas fetus infection in cats.

    Treatment of asymptomatic cats is not recommended, but in a multi-feline setting where cats show clinical symptoms, vets find it more efficient to treat all of them together. You should also treat giardia in cats that have come into contact with someone who has been vaccinated.

    Your responsibility doesn’t end after treating your cat. In addition to treating infected cats, environmental management is also important to prevent the infection from emerging again after treatment.

    Do not try to determine the kind of treatment required for your cat by yourself. Veterinarians know what is best to treat giardia in cats, so let them decide for your cat’s welfare.

    Giardia cysts are transmitted as soon as they enter the environment. That’s why stools must be passed quickly and removed from the environment. To prevent giardia in cats, you must bathe them every day to get rid of cysts lying in their fur.

    What is the prognosis for giardiasis?

    All About Giardia in Cats

    In most cases, the prognosis is good. Fatigue in older cats and those with weakened immune systems have a greater risk of complications and death. Your cat must be tested again after 2-4 weeks after the first treatment.

    How is Giardia diagnosed?

    Giardia in Cats | Small Door Veterinary

    A regular stool examination cannot detect these small, isolated cysts passed along with the stool. To detect giardia in cats effectively, you’ll need a zinc sulfate floatation solution. Mostly, parasites can be found directly in the fecal smear. You’ll need to test the stool sample for giardia-specific antigens (cellular proteins) on your veterinarian’s prescription.

    Some Giardia tests can be done clinically, while others require a reference laboratory. Many cases are thought to be diagnosed based on the history and clinical signs of giardiasis.

    Giardia in cats is diagnosed by direct swab test (wet test), stool bleeding, stool ELISA, direct swab immunofluorescence, and PCR.

    The plant parasite comes out with fresh fecal matter. The smear is taken and tested. A small amount of freshly excreted stool or mucus is mixed with a drop of salt on a glass slide and then immediately examined under a microscope with a glass of 100 power. A duodenal view can be obtained during the endoscopy of microtubules and tested for the trophic form. However, giardia in cats tends to remain in the small intestine irrespective of endoscopic intubation.

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    Flotation with zinc sulfate is recommended for stool examination. Ulcerative excretion is irregular and requires examining multiple stool samples (usually three) (continuous or intermittent). Traditional methods of using salt or sucrose to distort the cyst are unnecessary.

    Although this test is not widely used in Europe, you can also use direct immunofluorescence techniques to detect cysts in the stool.

    ELISA techniques, including the SNAP test, can be used to detect antigens in feces. These methods do not test with much care as opposed to other regular fecal tests. Much research has proven that the detection of ELISA antigens yields better direct immunofluorescence results.

    Polymerase chain reaction (PCR) testing is possible but not widely used. The advantage is that you can detect all types of bacteria. Early PCR-based studies showed high positivity (up to 80%), raising concerns that PCR tests could detect clinically irrelevant infections. However, few real-time PCR measurements can be used to diagnose Giardia in cats. Recent studies have shown that other methods have higher effectiveness.

    Fecal floatation tests have been standard tests for a long time. Still, stool antigen tests are equally sensitive, specific, and easy to carry out. Stool sample testing has the advantage of being inexpensive and identifying other potential parasites. Still, in practice, they are less common and less sensitive.

    Doctors often use convenient methods instead of complicated tests to evaluate response to treatment. But this approach should be avoided as there is a risk that antibiotics will alter the intestinal microflora. Also, co-infection with other parasites such as Tritrichomonas Felidae and Cryptosporidium is common and should be treated appropriately depending on the assessment results.

    Prevalence of giardia in cats

    All About Giardia in Cats

    Giardia is common worldwide and can be found throughout the United States. Although giardia in cats is spread over a great population, it depends on many factors such as living conditions, collective animals, breeding areas, refugee animals, stray animals, location, and method of diagnosis.

    In a patient-side antigen testing study of symptomatic cats in the United States, 10.8% (512/4977) of cats were Giardia positive.

    Another study confirmed Giardia infection in 31% (36/117) of cats tested on international standards.

    In 2020, the prevalence of Giardia in American cats was 4%. They tested for the presence of giardia in a reference laboratory with more than 1.8 million stool samples. However, stray dogs or cats were not considered. Not all veterinary hospitals use reference laboratories, so at least 4% of asymptomatic patients can be considered an initial prevalence.

    Prevention of giardia in cats


    All About Giardia in Cats

    Despite the various methods to treat giardia, it cannot be completely eradicated because the cyst becomes infected as soon as it is shed, causing reinfection. This is why fecal contamination must be prevented in the environment to prevent re-infection.

    1. Bath your cat to remove feces from the fur. We also recommend home disinfection or sanitation, especially the boxes, litter boxes, and mattresses. Keep supplies of quaternary ammonium products, boiling water, and chlorine as they help treat cysts.

    2. Intensive washing of a contaminated environment and the use of 4-chloro-m-cresol (chlorocresol) or quaternary ammonium compounds help restrict the spread of giardia in cat shelters re-infection.

    3. You should remove contaminated animal excrement, and containers and surfaces should be cleaned and sanitized with quaternary ammonium compounds. Keeping the cat out of reach from its furs after being groomed might also help to prevent re-infection.

    4. Washing the cat or its surroundings with chlorhexidine shampoo at the beginning and end of treatment may help eliminate the cyst.

    5. Testing may be suggested for the new cat before entering a cat home environment to prevent parasite infestation. Isolating the cats or keeping them in quarantine before interaction with the multi-cat surrounding can help.

    6. Nursing staff (nurses, veterinarians, veterinary students) are expected to know and follow health regulations.

    7. Inactivated vaccines are used widely in the United States but not in Europe. Used both for treatment and prevention, this has been proven very effective for fighting against giardia.

    Importance of molecular testing for giardia

    How to Treat Giardia in Cats

    Molecular testing must be performed in commercial laboratories to determine the total number of animals infected with Giardia. The potentiality of your cat’s giardia infection depends on the kind of living condition it dwells in.

    Although there are reports of feline infections in which humans and animals can coexist, care must be taken towards infected F-compatible host populations where humans and animals are unlikely to coexist. So there are fewer chances of the infection spreading to the owners.

    Family members with severe immunodeficiency are at greater risk, but maintaining pet and human hygiene can reduce the risk.

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    Can my cat spread giardia to me or my family?

    Amongst all other parasitic infections, giardia affecting the intestines is most common and can be transmitted from cats to humans. For a long time, domesticated animals like cats, dogs, and wild animals were considered the main causes of human infection.

    Though there is a specific genotype A of giardia that can infect humans, dogs, and cats, genotype B can infect only humans and dogs. However, human-to-human transmission is also significant, and polluted municipal water resources are responsible for most contamination.

    Giardia in cats can be diagnosed with proper environmental disinfection and maintaining personal hygiene. These are very important to prevent accidental transmission to humans. People with certain diseases such as AIDS and cancer, or those taking chemotherapy, should be very careful, especially when dealing with their pet’s stools and waste products or after feeding their medications.

    You can use a 1:32 or 1:16 solution or 1-2 cups diluting with water (60-120 ml per liter). But always ensure whether the exposed surfaces and buildings can be safely treated with bleach. Quadrisol and ammonium compounds (such as Parvosol) are also known to kill giardia cysts. Giardia cysts tend to dry out, so keep the surroundings as dry as possible.

    Always thoroughly clean your pet day and night and before bringing new pets, sanitize the environment and let it dry out for a few days.

    Eliminating Giardia

    According to the CDC, if a cat is diagnosed with giardia, disinfecting the environment is essential to prevent reinfection. Always remove the cat from the potential infection site. Clean the area with a bleach solution diluted with 1 liter of water. It can also be dried or washed with a dry or clean quaternary ammonium disinfectant. Giardia cysts are easy to eliminate when dry, so keep them as dry as possible for a few days.

    Cat fur can also cause Giardia. Make sure to thoroughly wash the coat with shampoo to remove the cysts carried in the furs. Wash again with a quaternary ammonium disinfectant to remove harmful organic matter. But remember, prolonged exposure to this chemical can irritate your cat’s skin and mucous membranes, so do not extend it for more than 3-5 minutes.

    After showering, pay special attention to the anal area and wash the solution thoroughly. Bathing is often a difficult task, so you should ask your vet to lend you a hand in this. If your cat is exposed to much stress, your veterinarian may prescribe mild anesthesia.

    Giardia is difficult to eradicate in an already infected environment, but it doesn’t mean you can’t at all! You can always cut down the number of times your cat gets sick or infected and even from re-infection. Although the risk of getting Giardia from cats and dogs is low, there are steps you can take to mitigate the risk.

    1. Always use disposable gloves for your home sanitization process.

    2. Remove the stool and place it in a plastic bag. Clean the surface with soap or detergent. Wash the surface thoroughly so that no dirt is visible, reducing the chances of contamination.

    3. If the area or object is dirty, clean it with soap, water, or other detergents. Then use a household disinfectant and follow the instructions on the label for safe and correct usage.

    4. Take precautions against keeping surfaces wet for some time

    5. Wear gloves, and ensure proper storage of the disinfectants.

    6. Ensure the product has good breathability while using it on soft (porous) surfaces (carpets, rugs, curtains, etc.)

    7. If you find the stool on fabric materials like carpet or any furniture, use products that have good absorbing powers (such as double paper towels)

    8. Dump the stool in a plastic bag and discard it

    9. Wipe the infected area with regular detergent or carpet, or for better results, wash off the carpet or rug.

    10. Allow the area to dry completely.

    11. Always read the product label for safe usage and follow everything that’s mentioned.

    12. If your dog or cat is being treated for giardia, the environment should be cleaned daily. You can disinfect food containers in a dishwasher.

    13. If you don’t have a dishwasher, keep them immersed in boiling water for at least 1 minute (simmer for 3 minutes at altitudes above 6500 feet).

    14. Clothes, pet supplies (sheets and stuffed animals, etc.), and bedding can be machine washed and dried in the best possible way for 30 minutes. Dry clothes completely in direct sunlight.

    So far, drugs that prevent giardia in cats have not been identified. Giardia vaccines have been reported, but there is no definite way to ensure their efficiency. One study found that vaccinated kittens were unaffected by the infection even after 6 to 12 months. Still, the vaccine caused certain side effects and caused other problems in the body. Other studies have shown that the vaccine is ineffective in already infected cats and may not prevent reinfection.

    So, the last word would be to control the environment. This includes disinfecting potentially infected areas of your home or checking your cat’s fur for giardia. Also, keep a regular check on your cat’s natural behavior and health. Please consult your veterinarian when you notice any change in its body or nature, as prevention is always better than cure.


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