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Giardia: A Parasite Of Many Species

If you have a friend who camps or fishes, you may have heard that they 
had been infected with Giardia. Or your veterinarian may have told you 
that your cat or dog had Giardia. In either case, you probably wondered, 
can I catch it as well?

Giardia is a protozoan parasite (one-celled organism) that can infect a 
variety of species, including pets and people. The human form of Giardia 
really likes people, the canine form likes dogs, the feline form likes cats, 
and the ruminant form likes cows and sheep. But it is possible for any of the 
forms to infect any of the other species.

In an animal or a person, Giardia lives in the intestinal tract. It may cause 
no symptoms, especially at first, but with time and as the organism becomes 
more numerous as it propagates, diarrhea commonly occurs. Some people 
may have more long standing or severe disease; then the symptoms can 
also include abdominal cramping, nausea, vomiting, loss of appetite, and 
weight loss.  Pets also get diarrhea when infected, but they tend to get 
diagnosed faster as it is common to do regular fecal testing in veterinary 

Giardia cysts are passed in the feces of infected animals and people.  
These cysts are resistant to environmental extremes, and thus can live in 
feces or fecal contaminated soil, surfaces, and especially water, for a long 

Pets and people are usually exposed from contaminated sources in the
environment.  Giardia is a common cause of recreational water illness, 
from pools, water parks, water play areas, hot tubs, lakes, rivers, ponds, 
streams, and oceans. Pets and people swallowing even a small amount of 
water can become infected. You share the water, and the germs in it, with 
every person or animal who enters that water. The infective Giardia cysts 
can also be present on other surfaces contaminated with feces such as 
bathroom fixtures, changing tables, diaper pails, and toys. Uncooked, 
fresh produce can be contaminated as well.      

Luckily, Giardia is easily diagnosed in veterinary medicine. There are two 
tests commonly performed: a microscope test call an "ova and parasite" 
(O&P) where the technician looks for the presence of the parasite in a 
solution made from the feces and then centrifuged. The other test also 
uses a stool sample, but uses a more sophisticated method to check for 
any DNA of the Giardia parasite.

Treatment is usually very rewarding. Drugs commonly used are 
metronidazole or fenbendazole, although in stubborn cases they may 
be used at the same time.

What can you do to prevent infection in the first place?  Have your pets' 
stool checked regularly for parasites (at least twice yearly). Practice strict 
hygiene, cleaning surfaces that could become contaminated by stool. Wash 
your hands after going to the bathroom, and insist your children do as well. 
Every day, place any dog and cat feces from your property into plastic bags 
that will go to a landfill. If you have a pool, keep it well maintained, don't 
allow any person or pet in the pool if they have diarrhea, and have everyone 
shower (with soap) before entering the pool. Don't allow children to defecate 
while in the pool. Don't swallow any water when you are in a pool or any 
other type of recreational water. Wash all produce well before consuming.

Giardia is a common parasite. Your veterinarian can check your pets for 
Giardia by performing a stool test, and treat if necessary. You can prevent  
your family from being infected by some common sense, good hygiene 

Companion Animal Parasite Council
Centers for Disease Control and Prevention 

What About the Pool?

1. Giardia can live for up to an hour even in a well-maintained pool, 
    and much longer, potentially forever, in a poorly maintained pool.
2.  Keep your pool in the best condition by checking the pH and chlorine levels
     regularly. You can obtain test strips at a home improvement store, but you 
     should check the expiration dates.
3. The chlorine level should be 1 to 3 ppm.
4. The pH should be in the 7.2 to 7.8 range.
5. Don't allow your dogs into the pool unless they have a negative stool test.
6. Don't allow anyone (people or pets) into the pool if they have diarrhea.
7. People should practice good hygiene before entering the pool and while in 
    the pool.

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