Geophagia is not associated with Trichuris or hookworm transmission in Zanzibar, Tanzania

Abstract

SummaryGeophagia may be harmful as a method for the transmission of geohelminths. In this study, we pose two questions in a representative sample of 970 pregnant women from Pemba Island, Zanzibar, Tanzania. Can consumed earth be a vector for geohelminth infection? And do geophagists have differential parasitic infection? The parasitological content of 59 non-food substance samples was analysed. Cross-sectional data regarding pica behaviour were collected through interviews conducted by local researchers. Ascaris, Trichuris and hookworm status was ascertained through Kato-Katz smears. The prevalence of geophagia at baseline was 5.6% and the overall prevalence of Ascaris, Trichuris and hookworm infection was 5.6%, 33.2% and 32.9%, respectively. No consumed soil samples contained infectious parasitic stages, and only one of the consumed pica substances (charcoal) contained parasites of potential risk to human health. Neither the prevalence nor the intensity of infection with Ascaris, Trichuris or hookworm differed significantly by geophagia status. Furthermore, in multivariate models, geophagia was not a significant predictor of helminth infection status. We conclude that geophagia is not a source of Trichuris or hookworm infection among pregnant women in Pemba (insufficient power to evaluate the effect of Ascaris), which is in contrast to existing findings of helminth infection and geophagia. KeywordsPica; Geophagia; Helminthiasis; Pregnancy; Parasites; Zanzibar * Corresponding author. Tel.: +1 607 351 0172; fax: +1 607 255 1033. E-mail address: sly3@cornell.edu (S.L. Young). Authors' contributions: SLY conceived the substudy design, oversaw sample collection, collected ethnographic data and drafted the paper; DG determined sample preservation methods, examined pica samples, interpreted parasitology results and wrote the parasitology methods; THF designed and supervised the parasitological sample collection and analysis, and assisted with data analysis and drafting the paper; SMA assisted with substudy design, researcher training and pica sample collection;

Association of Pica with Anemia and Gastrointestinal Distress among Pregnant Women in Zanzibar, Tanzania

“…Hookworm was not included for three reasons: it greatly limited the sample size, the effects of hookworm on iron status are largely captured by the inclusion of Hb, and we have already established that geophagy is not a vector for hookworm transmission in this population. 15 Women with lower Hb concentrations, women who were later in gestation, and women who had experienced abdominal pain or nausea were more likely to engage in pica. Older women and women whose husbands had received formal education were less likely to engage in pica.…”

“…In Pemba, as in most parts of the world, earths are carefully selected and prepared by heating or cleaning before consumption. 15,29 Pica behaviors were asked about at multiple time points, including at any time during the current pregnancy, at the time of the baseline interview, and two weeks after delivery. Information on current pica practices was available for 2,367 of the 2,368 women enrolled, and on post-partum pica practices for 1,578 of the sample (66.7%).…”

“…Investigators from diverse fields have explored its causal role in conditions such as heavy metal poisoning, especially lead, 7,8 micronutrient imbalances (by binding with consumed food or preventing adsorption in the small intestine), [9][10][11][12] and transmission of parasites. [13][14][15] Others have studied its positive health effects, such as providing micronutrients, 12,16,17 soothing gastrointestinal upset 18 or preventing harmful chemicals or pathogens from entering the bloodstream. [18][19][20] An additional reason to study pica is that those who most commonly engage in pica are the most physiologically vulnerable: pregnant women and young children.…”

“…[21][22][23][24] In this study, we characterized geophagy and amylophagy in a population that was known to engage in pica. 15 We examined the cross-sectional associations of pica with sociodemographic factors, diet, parasite burden, and gastrointestinal morbidities.…”

“…We know that Pemban pica substances are unlikely vectors for geohelminths; parasitologic analyses of geophagic earths on Pemba indicated no viable Trichuris , Ascaris , or hookworm eggs. 15 Moreover, the desiccating effect of uncooked rice on hookworm eggs makes it unlikely that uncooked rice would harbor viable hookworm eggs (Goodman D, unpublished data, 2006).We explored the possibility of differential effects of pica on heme versus non-heme iron absorption by testing for interactions between number of servings of heme and inorganic iron foods and pica behavior on Hb concentration, but no significant interactions were found. This finding could be an indication that pica substances affect adsorption of both types of iron similarly or do not affect it at all.…”