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  • Giardiasis

  • Giardiasis is an intestinal infection in humans and animals, caused by a protozoan parasite Giardia duodenalis (also known as G. intestinalis or G. lamblia).

    "...it is not a "worm", bacteria or virus."
    Giardia is passed in the feces of animals in the form of a cyst that is resistant to many environmental extremes. These cysts are scattered through the environment in feces or fecal-contaminated water. These cysts are infectious when passed, and upon ingestion by the next host, the encysted trophozoites emerge from the cysts in the intestinal tract. Within the intestine, the trophozoites feed and multiply. Some trophozoites will then form a cyst wall around themselves, and those cysts will be passed in the feces to continue the cycle.

    How Do Dogs, Cats, and People Become Infected?

    People are typically infected with a human form of Giardia, dogs with a canine form, cats with a feline form, and cattle
    and sheep with a ruminant form. People are occasionally infected with a different form that is shared with animals. On
    rare occasions dogs and cats have been found infected with the human form. Thus, there is little evidence for direct
    transmission from pet dogs and cats to people. However, the rare occurrence of the human forms in cats and dogs
    means that there may be a slight chance that they pose a risk as a source of human infection.

    To be able to distinguish the specific forms, the veterinarian is required to submit samples for specialized tests.

    Symptoms of Infection

    In dogs and cats, infection with Giardia is usually asymptomatic. Some pets will, however, develop persistent diarrhea. There is usually no blood in the stool.

    In people, infection with Giardia also is often asymptomatic. However, some people can develop acute, intermittent, or chronic nonbloody diarrhea. Other symptoms in people include abdominal cramping, nausea, vomiting, loss of appetite, and weight loss.

    Prevention and Treatment

    Unlike for heartworm disease, there are no drugs that can be routinely given to a pet that will prevent infection.

    • Dogs, cats, and people that have symptoms of the infection can be treated; however, there are situations where it is difficult to clear an animal of their infections.
    • There are approved drugs for treating the infection in people. These drugs have not been approved for this specific use in dogs and cats, but these and similar drugs are used in them.