About Giardia
1) Q - I
have heard a lot about giardia, but what is it?
A - Its full name is Giardia lamblia, first described by Leeuwenhoeck,
the inventor of the microscope, in 1681. It is a parasite, which causes
an illness called giardiasis, also known as "beaver fever" or "backpacker's
diarrhea". The onset of symptoms may be abrupt, including watery diarrhea
with abdominal cramps, terrible flatulence, nausea with or without vomiting,
fatigue and possibly fever. The onset may also be gradual with the slow
development of loose, soft and foul smelling stools, at times intermittent
with watery stools or even constipation. Other less common symptoms may
include: heartburn, indigestion, bloating, feeling of fullness after eating
very little and unintentional weight loss over time. The initial, typically
more pronounced symptoms tend to last 3 to 4 days and occur anywhere from
1 to 3 weeks after exposure to the parasite.
2) Q - Where does giardia come from?
A- Giardia likes to hang out in water sources such as beaver ponds and
mountain streams. It can exist in a live and active form or as cyst in
a dormant form, remaining viable for up to 2 to 3 months in cold water.
Actually the first known water-borne outbreak in the U.S. was in Aspen
in 1964. A few towns in Colorado known to have recent outbreaks include
Aspen, Vail, and Estes Park. The mountain regions of the West including
the Rockies, Cascades and Sierra Nevada are all considered endemic areas
(where a disease is continually present in a region).
3) Q - Who does Giardia affect and who is most susceptible?
A- There are different types of giardia, but it appears that the same
type can be transmitted between humans and animals, which categorizes
the disease as a zoonosis. Giardia has been known to infect beavers, dogs,
rodents and big horn sheep from cysts passed in human stools and to infect
humans from the feces of beavers, dogs and mule deer. Decreased stomach
acidity, immunodeficiency, blood type A and poor nutrition can all contribute
to an increased risk of a person having symptoms with the parasite infection.
4) Q - How is giardiasis diagnosed?
A- The most common test involves collecting 3 stool samples taken with
2 day intervals and sending them to a lab for examination for the cysts
or parasite bodies. Another less commonly used procedure is called the
string test in which a string, tied to a gelatin capsule, is swallowed
and retrieved 4 to 6 hours later. It is then examined for the parasites.
Probably the most reliable, but by far the test least performed is a biopsy
of the small intestine. Blood tests to evaluate the immune response to
giardia have been studied, but are not in common use. More advanced studies
of stool samples have also been investigated using fluorescence, but are
not in widespread use yet.
5) Q - Can someone be infected without knowing it?
A- Many people can be carriers and in fact, most infections cause no symptoms.
The presence of symptoms is variable and estimated to occur in 5% to 70%
of individuals infected. Resistance can be acquired as evidenced by lower
rates of infection and illness within local populations where giardia
is known to be endemic as compared to visitors of the same region. .
6) Q - How is giardiasis transmitted?
A- As previously mentioned in question 3, giardia can be transmitted from
animals to humans or vice versa. Transmission or spread of the disease
is by the oral-fecal route, usually by consumption of water from a contaminated
source, infected by feces. It is believed that person-to-person is the
most prevalent means of transmission. It is estimated that 25% of family
members with infected children become infected. Also reported are epidemics
and carrier rates of 30 to 60% in day care centers and Native American
reservations.
7) Q- Is the public water supply safe?
A- You may have heard about recent news involving a potential giardia
contamination of the water supply of Greeley. After speaking with Connie
O'Niell, a water specialist from the Weld County Department of Health,
it turns out that on standard yearly testing of the water supply, 1 viable
cyst was detected in a finished water sample on August 31st. For the next
three days a water boil alert was sent out to residents of Greeley, Evans
and Windsor while further testing was done. During those days the water
source was changed from the Poudre Valley/Boyd Lake to the Horsetooth
reservoir. Ultimately, the source of the cyst was determined to be the
back flushing of a sand filter. After this discovery, the boil alert ended
and the original water source was reinstated. I also spoke with Stan Kiersztyn,
a plant operator for the Telluride Water Treatment Plant who informed
me of yearly water testing mandated by the state. He reported that a 1000
gallons of water a flushed through a mesh filter, which is then sent to
a lab in Denver. According to Stan, no giardia cysts have been isolated
in the raw or finished samples from the Telluride water supply.
8) Q - Is there a treatment for giardiasis?
A- There are several drugs which can be used in the treatment of giardiasis.
They include 3 classes: Nitroimidazoles (metronidazole(Flagyl), tinidazole,ornidazole
and nimorazole), nitrofuran derivatives(furazolidone) and acridine compounds(mepacrine
and quinacrine). Not one medication alone has proven to be effective in
all cases, but in situations of resistant infections or recurrent infections,
combination drug therapy or single medication long term courses can be
employed. Quinacrine has a success rate of about 95%, but tends to be
used less often due to higher occurrence of side effects compared to metronidazole.
This medication, although not formally approved for this application,
is tolerated better and has comparable efficacy of 85 to 90%.
9) Q - How can giardiasis be prevented?
A- Boiling water, drinking bottled water, or the use of an effective filter
when camping or back packing in the woods will help to reduce your chances
of exposure. A vaccine for dogs, new this year, called GiardiaVax was
developed by Dr. Merle Olson of the University of Calgary. It was licensed
by American Home Health and is currently being marketed through Fort Dodge
Animal Health. The vaccine is available through your local veterinarian.
I did speak with Dr.Lisa Malloy, a veterinarian in Telluride, who reported
good success with the vaccine so far, stating that the recurrence rate
in the same animals was noticeably lower. I also spoke with a Dr.Bigby
of Fort Dodge Animal Health, who informed me that approval for a feline
version, called Felivax Giardia, was just obtained and should be marketed
sometime this year.
10) Q - Is a human vaccine against Giardia available?
A- After contacting many pharmaceutical companies, I was ultimately unable
to determine if research is currently underway toward the development
of a human vaccine.
11) Q - How do I find out more about this most unpleasant neighbor of ours?
A- The resources I found to be most helpful included medical texts, phone
interviews, and the internet. A well written chapter on infectious diarrhea
from wilderness and foreign travel can be found in the Wilderness Medicine
text, 3rd Edition, edited by P. Auerbach, pp.1048-51. Phone interviews
were conducted with Stan Kiersztyn a plant operator at the Telluride Water
Treatment Plant, Dr. Lisa Malloy, a local veterinarian, Dr. Bigby of Ft.
Dodge Animal Health, and Mrs.Connie O'Neill, a water specialist for the
Weld County Dept. of Health. On the internet, I found no helpful comprehensive
resources, but I would recommend a topic search on giardia using a common
search engine for answers to specific questions.
I would like to thank Drs. Jane Reldan, Kent Gaylord, Howard Donner and
all the staff at the Telluride Medical Center for their hospitality. I
also enjoyed meeting many of you, as patients or residents of the Telluride
community. A return visit is already in the planning stages for the winter
of 2000. Until then, I bid you all adieu! David S. Snodgrass, M.D
