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Is Giardia zoonotic?

Thu Mar 25 12:57:18 EST 1999

Dear Group:

I have gone from believing that Giardia was zoonotic (beavers, especially) to believing that each host species had its own pet Giardia, to having just found the following news release suggesting that Giardia is right up there with Toxocara canis as major pet or companion animal pathogens shared with their care givers.  Comments welcomed.

Steve Kayes

----------------<press release story follows; long article>---------
              Pets Can Now Be Protected
              from Disease that Also Afflicts
              Humans Fort Dodge Animal
              Health Introduces Vaccine


              OVERLAND PARK, Kan., March 22 /PRNewswire/ -- "Intestinal
              parasite" is not a phrase that anyone wants associated with their
              family's health -- including their pet's. But did you know that your
              pet might put your family at risk of becoming infected with an
              intestinal parasite? Especially if your pet is infected with a parasite
              like Giardia -- one of the most significant waterborne protozoal
              illnesses in the United States, which infects both pets and humans. 

              Now there is a vaccine available to help break the cycle of Giardia
              infection in dogs. Fort Dodge Animal Health has received USDA
              approval for the release of GiardiaVax(TM), the first vaccine to be
              used in dogs as an aid in the prevention of disease and cyst
              shedding caused by the protozoal parasite Giardia. (For
              information, call toll-free 877-444-5567). 

              It has been estimated that nearly 36 to 50 percent of puppies, 10
              percent of well-treated adult dogs, and up to 100 percent of dogs in
              breeding kennels are infected with Giardia.(1) In a recent
              unprecedented field study sponsored by Fort Dodge Animal Health
              involving more than 7,500 pets, it is estimated that as many as one
              out of eight pets seen by a veterinarian may be infected with

              Giardia is a one-celled, microscopic parasite that lives in many
              different and often unexpected water sources, including ponds,
              lakes, streams, backyard swimming pools and even tap water.
              Giardia has even been found on contaminated animal haircoats.
              When ingested, it infects the intestinal tract of pets and humans,
              causing fever, vomiting and diarrhea, as well as other potentially
              serious and painful gastrointestinal problems. 

              Although any pet can contract the disease, dogs most at risk of
              becoming infected with Giardia include puppies, outdoor dogs,
              hunting dogs, farm dogs, city dogs, adopted strays, dogs that live in
              kennels and dogs in multi-pet households. Many researchers
              believe there is even the possibility of transfer of Giardia infection
              between pets and people. 

              "If I have an animal who has tested positive for Giardia and there
              are children in the household, I recommend treating the patient.
              And, if the animal is one that would be contaminating the
              environment, we always warn the clients that this animal could
              contaminate water supplies and the patient (dog) should be
              treated," said Dr. David Twedt, professor of small animal
              medicine, Department of Sciences at Colorado State University. 

              Pets, like humans, become infected with Giardia through fecal-oral
              contact, or, when they ingest infective cysts in contaminated water
              from streams, lakes, ponds, puddles, wells, and tap water. Another
              method of infection includes grooming contaminated haircoats.
              Cysts develop into feeding trophozoites which reproduce and
              which can cause disease symptoms. The trophozoites then form

              Large numbers of cysts are then passed again to the environment
              in the infected dog's feces within a short time; a cycle that
              perpetuates environmental contamination. The Cycle of Infection 

              Once Giardia cysts are passed back into the environment, they can
              live for up to two months in temperatures of 46 degrees Fahrenheit
              and one month in temperatures up to 70 degrees. Researchers
              believe that this cyst shedding is the link to possible transfer of the
              infection to humans. 

              In a recent study by Dr. Andrew Thompson, professor of
              parasitology in the division of veterinary and biomedical sciences at
              Murdoch University, in Perth, Australia, Giardia isolates collected
              from both humans and domestic pets were examined. According to
              Thompson, Giardia isolates considered to be identical were found
              in both humans and companion animals, primarily in environments
              where pets were living in households with families. 

              "I think all the evidence is now suggesting that Giardia is zoonotic,
              and Giardia in companion animals can be transmitted to humans,"
              said Thompson. Diagnosis and Treatment Difficulties 

              When infected by Giardia, pets can show various symptoms,
              ranging from fever, vomiting and fatigue to severe diarrhea,
              cramping, dehydration and weight loss, but symptoms are not
              always obvious to pet owners. 

              To compound the difficulty of diagnosing Giardia, routine fecal
              analysis rarely detects infection from Giardia in pets. Giardia cysts
              are shed intermittently, so one negative stool sample does not rule
              out infection. This allows many infected pets to continue to go
              undetected and contaminate the environment. The contaminated
              environment then poses a threat to other pets in the household and
              potentially pet owners. 

              Treating Giardia infection in pets is not always effective. Current
              drug treatments do not guarantee success, and they do not prevent
              future disease in the pet. A Safe, Simple Solution 

              Pet owners now have a way to help break the cycle of Giardia
              infection in their dog. GiardiaVax is an inexpensive preventive
              measure available through your veterinarian that has been proven
              to be safe and effective in preventing the signs of disease and cyst
              shedding associated with Giardia infection. GiardiaVax can be
              given to healthy dogs, eight weeks of age or older. Two to three
              weeks later, they should receive a booster, then annually

              "GiardiaVax is a safe and easy solution to address the threat of
              Giardia infection in our dogs," said David R. Hustead, DVM,
              director of professional services at Fort Dodge Animal Health.
              "Although Giardia's prevalence in dogs is well-documented,
              oftentimes there are subtle signs in an infected dog, and the pet
              owner is unaware of the problem. This can cause a problem if the
              dog is contaminating the environment, posing a risk to other
              animals and potentially the pet owner. The use of GiardiaVax gives
              dog owners peace of mind in protecting their pet's health, and
              reducing the risk of environmental contamination." 

              For more information about GiardiaVax, pet owners should see
              their veterinarian, or call 877-444-5567. 

              Fort Dodge Animal Health is a division of American Home
              Products Corporation. American Home Products Corporation is
              one of the world's largest research-based pharmaceutical and
              health care products companies. It is a leader in the discovery,
              development, manufacturing and marketing of prescription drugs
              and over-the-counter medications. It is also a global leader in
              vaccines, biotechnology, agricultural products and animal health

              1. Barr SC, et al.1994. Giardiasis in Dogs and Cats. Compendium
              On Continuing Education for the Practicing Veterinarian. 16(5):

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