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Giardia and risk

Charles T. Faulkner ctfaulkn at utkux.utcc.utk.edu
Thu Mar 28 22:18:43 EST 1996

On Thu, 28 Mar 1996, Michael Casteel wrote:

> Somebody, anybody tell me what you think. Using Giardia lamblia as 
> an example, do you think that risk of exposure to this organism has 
> decreased since the 1960s due to an increase in our knowledge of 

	I was able to pull together a couple of references to share with 
those interested in following theis thread.

Jones, Smith and Eyles (1953) reported that the prevalance of Giardia in 
2 West Tenn communities was 10 and 9 % respectively (Trop Med Hyg 3:273).
They noted a drop from 19% prevalence when the communites were studied in 

Kappus and colleagues (1987, MMWR 40) reported that the prevalence of 
Giardia in 1987 was 7.2% compared with 4 % in a 1978 survey. The increase 
was noted in 39 states, and 7 reported a decrease in prevalence.  In 1991 
the prevalence decreased to 5.6 % (Kappus et al 1994, Trop Med Hyg 50:712).  

It is interesting that the trends in prevalence are not that 
different over the 30 year period despite the major changes in community 
hygiene.  The recent data, however, reflect cases compiled by 
State diagnostic labs and may represent a special "high risk" 
population of cases serious enough to require medical attention. The West 
Tenn data were compiled from community surveys and may be interpreted
as snapshots of community hygiene standards.  

Intuitively, I believe that Giardia prevalence is basically remaining 
constant at the 5 to 10% level, however it is the population at risk that is 
changing.  In 1953, the entire community was at risk. In the 1990's 
perhaps it is the family with a child in day care, the outdoor 
recreator drinking from Beaver inhabited streams, or the average pet owner.  
The take home message of Kappus et al's paper was that studies 
need to be conducted on defined populations if we are understand what 
factors are responsible for maintaining the parasite in the human 

Hope this is useful and stimulates other discussion. 

*      Charles T. Faulkner       *   Get your facts first and then you
*  Univ of Tennessee, Knoxville  *   can distort them as much as you please.
*     (ctfaulkner at utk.edu)       *                Mark Twain

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