in vitro culture and isoenzyme analysis of giardia lamblia

2.4 DISCUSSION
In terms of yield, it is recognised that retrieval of trophozoites from duodenal
aspirates is superior to attempting recovery of these stages through excystation of
cysts. In this study, however, the organisms were preferentially retrieved from
stools for various reasons. The intubation procedure or use of the string test
should be performed by a clinician I physician whose presence would then be
required during all collection times. Moreover, in random mass collections where
infection is not verified, duodenal aspirates would not be practically feasible and
thus collection of faecal specimens would be appropriate. Finally, donors, (who in
most cases were children and toddlers), might not have consented to repeated
intubation which is an unpleasant procedure.
The selected method did, nevertheless, present problems as stool collection and
screening were found to be time consuming. Obtaining a steady, reliable source of
Giardia lamblia cysts proved difficult. In many instances, stools were not readily
available from children when required and this resulted in irregular collections.
Since Giardia lamblia cyst production is intermittent, obtaining a faecal specimen
even from an infected individual is no guarantee of cyst recovery. Only a small
fraction of all screened stools were found to harbour Giardia cysts: 12,4% of 1023
were detected following formol-ether concentration and 1,2% by two examinations
of wet preparations. Some, even if positive on screening, were not suitable for use
in experiments due to very low cyst numbers and/or abnormal morphology (nonviable).
Seasonal patterns of Giardia occurrence have been documented in some
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