Intestinal parasitic infections: high prevalence of Giardia intestinalis in children living in an orphanage compared with hill-tribe children as detected by microscopy and ELISA

Background: Data regarding intestinal parasitic infections in preschool-aged children (less than 6 years old) living in an orphanage and remote mountainous areas are very limited.

Objectives: We surveyed infections in orphans and hill-tribe children.

Materials and Methods: They were studied in 2008 by stool examination (simple smear and concentration), Scotch-tape and culture (Boeck and Drbohlav’s Lock-Egg-Serum medium) techniques. The Giardia coproantigen ELISA was also performed. The risk correlation between unusual stool types and giardiasis by univariate analysis was tested.

Results: The overall infection rates in 137 orphans and in 145 hill-tribe children were 58.4% and 77.9%, respectively. Giardia intestinalis had the highest prevalence in orphans (with microscopy 28.5%, with copro-antigen ELISA 31.4%). Other pathogens included Blastocystis hominis (23.4%), Enterobius vermicularis (9.5%), and hookworm (0.7%), whereas the nonpathogens were Trichomonas hominis (19.0%), Entamoeba coli (11.7%), and Endolimax nana (2.2%). Ascaris lumbricoides had the highest prevalence (62.1%) in hill-tribe children, while Giardia intestinalis showed 7.6% with microscopy and 9.0% by ELISA. The other pathogens were E. vermicularis (25.5%), Trichuris trichiura (10.3%), B. hominis (2.8%), hookworm (1.4%), Sarcocystis hominis (1.4%) and E. histolytica (0.7%), whereas the nonpathogenic organisms were E. coli (19.3%), and E. nana (0.7%). Giardiasis stools from orphans had significantly greater cyst density than those from the hill-tribe children. The coproantigen ELISA for giardiasis demonstrated 91.4% specificity, 72.0% sensitivity, 64.3% positive predictive value, and 93.8% negative predictive value, respectively. By univariate analysis, a loose (mushy) stool type was 2.43 times likely to have Giardia cysts.

Conclusion: In large-scale epidemiological studies, a Giardia ELISA might be a useful aid for diagnosis, because conventional microscopy is time-consuming and relies on the expertise of the microscopist.