Giardiasis refers to an intestinal infection that is caused by the
protozoan parasite giardia. Dogs develop the infection by ingesting
(cysts) that are shed in another animal's feces. The contamination can be
from direct or indirect contact with the infected cysts. The organisms,
once ingested, make their way into the intestine, often causing diarrhea.
The treatment is typically performed on an outpatient basis with an ex
What is Giardia?
The Microscopic parasite clings to the
surface of the intestine, or floats free in the mucous lining the
intestine. Veterinary research documents suggest that 5% to 10% of all
dogs in North America have giardiasis at any given time.
Surveys also show that about 14% of the
adult dog population and over 30% of dogs under one year of age were
infected at some point during their life, and thus contributed to passing
along this intestinal infection to other dogs. Another Vet research
article I found suggests that 100% of kennel dogs, 50% of pups, and 10% of
well-cared for dogs carry giardia.
Life Cycle of Giardia
in two forms: a motile feeding stage that lives in the
intestine, and a non-motile cyst stage that passes in the feces. The
giardia trophozoite - which is the active stage of the organism - inhabits
the small intestine of the dog. The trophozoite stage is tear-drop shaped,
binucleated, and has four pairs of flagella. It attaches to the cells of
the intestine with its adhesive disc and rapidly divides to produce a
whole population of trophozoites. As they detach they may be swept down
the intestine. If intestinal flow is fast then they may appear in the
feces. However, if they have time, encystment occurs as the parasite
travels to the large intestine. The cyst is fairly resistant, and can
survive for several months outside of a host's body as long as sufficient
moisture is provided. The cyst is oblong in shape with four nuclei that
are sometimes distinctly visible. Mature cysts are usually found in the
feces of infected animals. Other animals become infected by ingesting the
cysts that passed from the body in feces. These ingested cysts then break
open inside the small intestine to release the motile feeding stage (trophozoite).
Giardia increase their numbers by each organism dividing in half which is
called binary fission
divide to produce a large population, then they begin to interfere with
the absorption of food. Clinical signs range from none in asymptomatic
carriers, to mild recurring diarrhea consisting of soft, light-colored
stools, to acute explosive diarrhea in severe cases. Other signs
associated with giardiasis are weight loss, listlessness, fatigue, mucus
in the stool, and anorexia. These signs are also associated with other
diseases of the intestinal tract, and are not specific to giardiasis.
These signs, together with the beginning of cyst shedding, begin about one
week post-infection. There may be additional signs of large intestinal
irritation, such as straining and even small amounts of blood in the
feces. Usually the blood picture of affected animals is normal, though
occasionally there is a slight increase in the number of white blood cells
and mild anemia. Without treatment, the condition may continue, either
chronically or intermittently, for weeks or months.
Giardia lives and reproduces in the small intestine of host animals. Giardia trophozoites, the free living stage of the organism, form infective cysts
that are passed out in the feces. If the cysts are present in a wet or
damp environment they can survive in a viable state for a few weeks to
several months. Giardia infections are transmitted via ingestion of
trophozoites or cysts in contaminated water or food. If a giardia cyst is
ingested, the cyst wall is broken down during the digestive process and
the trophozoite stage begins to colonize the upper small intestine.
Transmission also occurs by direct contact, especially with asymptomatic
carriers. More recently, giardiasis has also been recognized as being able
to be sexually transmitted. Giardia is so prevalent throughout North
America because it is highly contagious. The ingestion of as few as one or
more giardia cysts may cause the disease, as contrasted to most bacterial
illnesses where hundreds to thousands of organisms must be consumed to
produce illness. Up to 50 percent of young puppies will develop this
intestinal infection, and up to 100 percent of dogs housed in
kennels will develop it due to the massive exposure and
closely shared living spaces.
Diagnosis can be
done in one of two ways: via fecal sample by a Vet or via educated
evaluation of clinical findings by the breeder/owner or the Vet. Via fecal
sample is not straightforward. Even when a flare is at it's worst, the
cysts will not be shedding in every single stool. Therefore, a negative
report does not rule out giardia. The most thorough way to assess is to
collect a sample from every single stool produced for 48 to 72 hours and
have a Vet examine it using the giardia test kit.
The giardia test is a monoclonal antibody-based ELISA for the rapid
detection of Giardia lamblia cysts antigen in stool specimens and serves
as an in vitro aid in the diagnosis of giardiasis..
Infection may be
treated using one of a number of different drugs that are available
through a Vet Supply Store. The treatment of choice is with Metronidazole
250mg. Metronidazole has two interesting properties - the action is
largely confined to the gut and it also seems to stimulate the local
immune system. Metronidazole kills off the giardia and reduces the numbers
to the level the dog's immune system can handle. Alternatively, you may
want to use Fenbendazole (Safe-Guard or Panacur). Fenbendazole is a very
safe medication as a treatment for deworming your dogs. This is my second
choice for kennel use. The same dosage and three-day deworming treatment
using Fenbendazole for deworming dogs will also rid your dogs of the
Treatments from the Vet research literature that I found are shown in the
table below. Whatever treatment is chosen, it is very unlikely to
eliminate 100% of the infection in all dogs. Adaptations that may be made
to try to improve the success rate of a treatment regime include extending
the duration and dose of the treatment. Care must obviously be taken with
this approach to make sure that an adequate safety margin is always
maintained. Another approach is to retreat after an interval of one week.
Alternatively, repeat fecal samples may be collected one week after the
treatment and dogs which are still passing cysts can be identified and
treated. It should be recognized that, when treating a large number of
dogs, whichever of these treatment strategies is adopted, there may be one
or two dogs that remain as carriers of infection that will act as a
potential source for reintroducing the infection into your entire kennel.
||11.5 to 15 mg/lb BID**
||2 mg/lb BID*
||22 mg/lb once daily
||Safe-Guard or Panacur***
||22.5 to 25 mg/lb once daily
||12½ mg/lb BID
|Bid = Twice Daily
* Maximum daily dose 200 mg.
** Contraindicated in pregnancy
*** Licensed for the treatment of worm infections in dogs
I recommend that you
also see the page on Coccidiosis to learn more about the other
common protozoal infection called coccidiosis. No matter which
treatment you choose to utilize, the simple fact is that it
may not kill all of the cysts. A certain number of them can
burrow into the lining of the intestines and go dormant. They
can stay dormant for years. Due to the hard shell protecting
the cysts, it is almost impossible to kill them when they are
encysted in the lining of the intestines. Therefore, during
times of stress, the cysts may re-activate and start to
reproduce, causing another outbreak of giardiasis in your dog
or kennel. The amount of stress needed to cause a flare seems
to be highly variable with different dogs and dog breeds.
Since one of the highest incidences of the infection spreading is in a
kennel, boarding kennel and dog parks seek places that offer private
spaces for pets in order to avoid contamination from the other animals.
We hope these tips help you and your new
puppy enjoy a long healthy life!!