Giardia in Cats


Overview of Feline Giardia Infection

Giardia is a protozoan parasite found all over the world. It infects humans, many domestic animals and birds. Giardia lives in the intestinal tract and infection may be asymptomatic or can result in gastrointestinal symptoms.

Below is an overview of giardia infections in cats followed by in-depth information on the diagnosis, treatment and home care for this disease. 

Giardia infections (called Giardiasis) show no gender or breed predilection but are most common in young cats and in cats under close confinement, such as those in kennels, animal shelters and pet stores.

Most cases of Giardia infection in humans arise from person-to-person contact or from contaminated water, but animals do harbor strains of Giardia that are infectious to humans and animal-to-human transmission theoretically is possible.

What to Watch For

Cats may display any or all of the following symptoms: 

  • Diarrhea
  • Vomiting
  • Weight loss
  • Flatulence (excessive gas)
  • Diagnosis of Giardia in Cats

    Veterinary care should include diagnostic tests and subsequent recommendations. Diagnostic tests are needed to recognize Giardiasis and exclude other diseases. Tests may include:

  • Direct fecal smears to look for two different stages of the Giardia organism called “cysts” or “trophozoites.” A positive direct smear results in a conclusive diagnosis of Giardiasis, but direct fecal smears may be negative in infected animals.
  • A zinc sulfate concentration test to identify Giardia cysts.
  • An enzyme-linked immunosorbent assay (ELISA) test to identify Giardia antigens in the stool.
  • Direct immunofluoresence test to identify Giardia cysts in feces.
  • Collection of samples from the duodenum (first part of the small intestine) during endoscopy and examination for Giardia trophozoites.
  • Treatment of Giardia in Cats

    Treatment for pets with Giardia infection may include one or more of the following drugs:

  • Metronidazole
  • Fenbendazole
  • A combination of praziquantel, pyrantel and febantel
  •  If your cat fails to respond to Giardia treatment and continues to have signs – please consider Tritrichomonas Foetus Infection.
  • Home Care and Prevention

    Administer as directed all medications prescribed by your veterinarian. All of the prescribed medication should be given to insure elimination of the infection. A high-fiber diet may improve stool consistency in pets with diarrhea associated with Giardia infection.

    Decontamination of the environment is an important part of preventing infection. In multiple-cat households and in situations in which animals are under close confinement (e.g. kennels, animal shelters, pet stores), proper sanitation is crucial to prevent cross-contamination from one animal to another. All fecal material must be removed from cages, runs and yards. Kennels must be cleaned with appropriate disinfectants and totally dried before allowing pets access to them.

    All animals should be treated with appropriate medication before being introduced into a multiple-animal environment.

    Bathing animals before introducing them into an uncontaminated environment allows for removal of feces and infective cysts from the hair coat.

    In-Depth Information on Giardia in Cats

    The protozoan parasite Giardia occurs in two forms. The active (motile) form that lives and multiplies in the intestinal tract is called a “trophozoite.” It can be recognized under the microscope by its characteristic appearance, which looks somewhat like a monkey face with two eyes and a nose. The trophozoite only lives in the intestine and cannot survive in the environment for any significant length of time. The other form is called a cyst and is the infective form of the parasite. Each cyst contains two completely formed trophozoites inside of it. Cysts can remain viable in the environment for many months and can cause infection if conditions are cool and moist.

    Cats are infected by ingesting cysts in the environment. Most infections arise from contaminated water, such as puddles, streams, lakes, shallow wells and water contaminated by feces.

    Giardia causes disease by damaging the small intestine, which leads to maldigestion (inability to break down nutrients properly) and malabsorption (inability to properly absorb digested nutrients). Giardia also increases intestinal motility, thus decreasing the amount of time the intestine can digest and absorb nutrients. Increased intestinal motility may be manifested by flatulence (excessive gas production) and diarrhea.

    The most common symptom of Giardia infection is diarrhea but there are many other causes of diarrhea. Some examples include:

  • Dietary disturbances: sudden changes in diet, overfeeding, dietary indiscretion, like getting into the garbage and eating too many table scraps
  • Drugs: aspirin and similar non-steroidal anti-inflammatory drugs such as ibuprofen; many antibiotics; anti-cancer drugs; heavy metals (lead, arsenic) and insecticides
  • Other parasites including worms (hookworms, roundworms, whipworms, tapeworms) and protozoa (coccidia, Entamoeba, Trichomonas, Balantidium)
  • Viruses: parvovirus, coronavirus
  • Bacteria: Salmonella, Campylobacter, Clostridium, E.coli
  • Obstruction of the intestinal tract by foreign bodies
  • Tumors of the intestinal tract
  • Mechanical obstruction of the intestinal tract caused by volvulus (twisting of the intestine) or intususception (telescoping of the intestine on itself)
  • Metabolic disorders such as kidney failure, liver failure and hypoadrenocorticism
  • Veterinary Care In-Depth of Giardia in Cats


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