Re: Giardia Lamblia and Giardiasis

On Sat, 26 Aug 2006 10:59:02 GMT, Mary Malmros
<malmrosnospam@xxxxxxxxxxxxxxxxx> wrote:

happy.when.hiking@xxxxxxxxxxxxxxxxxx wrote in
news:8jise25lj9hhb35bg37c44otb2pbpb7kvd@xxxxxxx:

[snip]
In summary: High Sierra water has too few Giardia cysts to pose a
genuine risk. Even if you drink water elsewhere where the
concentration is high, you probably won?t get giardiasis. If you do
get giardiasis, you probably won?t have any symptoms. If you have
symptoms, they will probably go away by them­selves in a week or so.
If they don?t or you develop serious persistent symptoms, you should
seek medical treatment. Finally, those contracting giardiasis may
develop immunity to it, thus lowering the likelihood that they will
get it again.

A couple of items of importance relevant to the discussion.
1) Robert L. Rockwell has never published anything on Giardia in a
referred scientific journal.
2) he has advanced degrees engineering; none in biology or medicine.
That gives him skill to organize information and write a logical
paragraph. That does not mean he can correctly evaluate the
information in a meaningful context. He is clealy confused about some
aspects of immunity and the role of antigens/antibodies.
3) Some of his statements on girardia vaccines are contradicted by
studies showing no significant clinical differences in giardia
infection in vaccinated cats or dogs. Studies done in 2003 and 2004
4) His use of citations is sporadic; some of his facts are supporetd
but others appear to come out of thin air.

Overall, I rate it as another selective use of facts mixed with
personal opinion to support a viewpoint.

The important things to keep in mind
1) hand washing (anywhere, not just in the backcountry) will greatly
reduce the rate of transmission
2) The prevalence of spores is low
3) If you get a bad case, 1 & 2 are irrelevant. Nothing else matters.

I had a friend who trivialized Giardia and cited a lot of the numbers
and information in the article. Then she spent 6 weeks with a case of
Giardia. She does not trivialize it any more.


I fail to see how you can "develop immunity" to a parasite. Perhaps
someone can explain that. Get as technical as you like, please; vague
terms like "develop resistance" won't convince me.
You don't really develop an immunity to anything in the common sense
of the word. You develop a immune response to the presence of a
specific foreign substance. It sounds picky but it's important. In
most cases the immune response will halt establishment of an infection
by killing or removing the invader before it has a chance to multiply.
In many cases you won't notice the symptoms or pass them off as caused
by something else. However, large infective doses usually trump
immune reactions.

There is a difference in the immune reaction to something that's in
the bloodstream as compared to something in the gut, airway or on the
skin. Getting into that topic requires far too much background
information to write up. It is dealt with reasonably well in
Janeway's Immunbiology (searchable on line at NCBI). However, the
basis for the Giardia symptoms is your immune system trying to
dislodge the invader. It is the immune response that causes the
majority of symptoms in many infections - redness, swelling, fever,
local heat, itching on the skin. In the upper airways, coughing,
sneezing to expel the invader. In the lower gut muscle contractions
resulting in expelling intestinal contents rapidly with lots of fluid
and mucus added to reduce parasite grasp of the intestial wall. If
you have symptoms you have an immune system response, it just isn't
adequate to remove the infective agent and symptoms will continue
until it is removed.

There are other mechanisms of killing parasites with less noticable
symptoms but this mechanism is not the primary response at this level
of infection. After a sensitizing exposure and adequate development
of antibodies, the less noticable reponse often predominates - but not
in everyone and it may require multiple exposures.

Cholera and other diseases with rapid onset of symptoms (hours), are
due to secreted toxins and that's a different ball game.



I got giardia and I didn't drink the water per se, but I'm sure I
ingested some -- it was a big-water Nepalese river filled with monsoon
runoff, and there were times I was upside down in it. At least one
other person on the same trip got it too. Never been so sick in my
life.

.

Relevant Pages

  • Re: Giardia Lamblia and Giardiasis
    ... most cases the immune response will halt establishment of an infection ... In many cases you won't notice the symptoms or pass them off as caused ...
    (rec.backcountry)
  • Re: Flawed tests conceal Bacteria infections ?
    ... bacteria died, the culture was mishandled, or another pathogen ... was responsible for the symptoms. ... Giardia is a protozoan, not a bacterium. ... an ear infection on the doctor's report. ...
    (sci.med)