Is Giardia zoonotic?
SKAYES at USAMAIL.USOUTHAL.EDU
Thu Mar 25 12:57:18 EST 1999
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.
----------------<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):
More information about the Parasite