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Objectives: To identify environmental factors that could serve to predict Ascaris lumbricoides infection patterns and thus guide control efforts in the absence of epidemiological information; to assess whether A. lumbricoides infection is positively associated with the soil clay content., Methods: Information on A. lumbricoides infection and re-infection in a cohort of primary schoolchildren and interview data on their socioeconomic background and behaviour were combined with environmental data using a geographical information system (GIS). Multivariate models served to explore the covariation of environmental and infection patterns adjusted for possible confounders., Results: Prevalence maps and spatial statistics revealed considerable spatial clustering of infection in the small study area. Logistic multivariate regression models showed strong positive associations of infection with vegetation density measured as the normalized difference vegetation index (NDVI) at baseline [odds ratio (OR) for a 10% increase: 1.82; 95% confidence interval (95% CI): 1.24-2.68; P=0.002] and after re-infection (OR: 2.22; 95% CI: 1.71-2.87; P<0.001). We also found a strong negative association of re-infection with the sun exposure of the soil surface as estimated from digital elevation models (OR: 0.78; 95% CI: 0.88; P<0.001). The soil clay content was only moderately positively associated with infection and re-infection. Socioeconomic and behavioural variables, although correlated with A. lumbricoides infection, did not appear to confound the above associations in the demographically homogeneous study area. Spatial analysis of the model residuals suggested that as the models accounted for most of the spatial pattern, the model standard errors should not be affected by spatial clustering., Conclusion: NDVI seems to have a high potential for the prediction of A. lumbricoides infection as it was strongly associated with infection patterns in the study area. Further advantages are that NDVI information is easy to use, affordable and available with global coverage.

To identify environmental factors that could serve to predictAscaris lumbricoidesinfection patterns and thus guide control efforts in the absence of epidemiological information; to assess whetherA. lumbricoidesinfection is positively associated with the soil clay content.Information onA. lumbricoidesinfection and re-infection in a cohort of primary schoolchildren and interview data on their socioeconomic background and behaviour were combined with environmental data using a geographical information system (GIS). Multivariate models served to explore the covariation of environmental and infection patterns adjusted for possible confounders.Prevalence maps and spatial statistics revealed considerable spatial clustering of infection in the small study area. Logistic multivariate regression models showed strong positive associations of infection with vegetation density measured as the normalized difference vegetation index (NDVI) at baseline [odds ratio (OR) for a 10% increase: 1.82; 95% confidence interval (95% CI): 1.24–2.68;P = 0.002] and after re-infection (OR: 2.22; 95% CI: 1.71–2.87;P < 0.001). We also found a strong negative association of re-infection with the sun exposure of the soil surface as estimated from digital elevation models (OR: 0.78; 95% CI: 0.88;P < 0.001). The soil clay content was only moderately positively associated with infection and re-infection. Socioeconomic and behavioural variables, although correlated withA. lumbricoidesinfection, did not appear to confound the above associations in the demographically homogeneous study area. Spatial analysis of the model residuals suggested that as the models accounted for most of the spatial pattern, the model standard errors should not be affected by spatial clustering.NDVI seems to have a high potential for the prediction ofA. lumbricoidesinfection as it was strongly associated with infection patterns in the study area. Further advantages are that NDVI information is easy to use, affordable and available with global coverage. [ABSTRACT FROM AUTHOR]

Background: Geohelminth infection is a major health problem of children from rural areas of developing countries. In an attempt to reduce this burden, the Department of Health of the province of KwaZulu-Natal (KZN) established in 1998 a programme for helminth control that aimed at regularly treating primary school children for schistosomiasis and intestinal helminths. This article describes the baseline situation and the effect of treatment on geohelminth infection in a rural part of the province. Methods: Grade 3 schoolchildren from Maputaland in northern KZN were examined for infections with hookworm, Ascaris lumbricoides, and Trichuris trichiura, treated twice with 400 mg albendazole and re-examined several times over one year after the first treatment in order to assess the impact of treatment and patterns of infection and re-infection. Results: The hookworm prevalence in the study population (83.2%) was considerably higher than in other parts of the province whereas T. trichiura and especially A. lumbricoides prevalences (57.2 and 19.4%, respectively) were much lower than elsewhere on the KZN coastal plain. Single dose treatment with albendazole was very effective against hookworm and A. lumbricoides with cure rates (CR) of 78.8 and 96.4% and egg reduction rates (ERR) of 93.2 and 97.7%, respectively. It was exceptionally ineffective against T. trichiura (CR = 12.7%, ERR = 24.8%). Re-infection with hookworm and A. lumbricoides over 29 weeks after treatment was considerable but still well below pre-treatment levels. Conclusion: High geohelminth prevalences and re-infection rates in the study population confirm the need for regular treatment of primary school children in the area. The low effectiveness of single course albendazole treatment against T. trichiura infection however demands consideration of alternative treatment approaches. [ABSTRACT FROM AUTHOR]

The social pattern of geophagy (soil-eating) and its possible role in the transmission of Ascaris lumbricoides, Trichuris trichiura and hookworm were investigated in a rural area of South Africa between March 1998 and July 1999. Schoolchildren (median age = 10 · 7 years; interquartile range 8 · 3–14 · 8 years) were examined for geohelminth infection at baseline and re-examined 3 and 29 weeks after treatment with albendazole. Interviews were conducted with the pupils in order to find out about their socio-economic background and their behaviour regarding geophagy. Soil-eating was less frequent in boys (39%), where it decreased with age, than in girls (53%), where no such age trend was apparent. The habit was more common in children from families of higher socio-economic status. The baseline prevalence of A. lumbricoides infection was higher in pupils who regularly ate soil from termite mounds (28%) when compared with non-geophageous pupils (19%; prevalence ratio (PR) = 1 · 46; 95% confidence interval (95% CI) 1 · 04–2 · 03). In contrast it was markedly lower in the groups who preferred eating tree termite soil (13%; PR = 0 · 67; 95% CI 0 · 43–1 · 04) or soil from other sources (8%; PR = 0 · 40; 95% CI 0 · 15–1 · 04). This pattern was still apparent after adjusting for possible confounders and was also found when analysing A. lumbricoides reinfection. In contrast, differences in prevalence of T. trichiura and hookworm infection between groups with different soil preference were small. [Copyright &y& Elsevier]

Schistosomiasis and soil-transmitted helminthiasis are among the most prevalent neglected tropical diseases and may lead to severe consequences. We assessed the extent of coinfection between Schistosoma haematobium and the soil-transmitted helminths (STHs) Ascaris lumbricoides and Trichuris trichiura in schoolgirls in the rural areas of KwaZulu-Natal, South Africa. We also explored if S. haematobium can serve as a predictor for soil-transmitted helminths in this area. From 15 selected schools, 726 primary schoolgirls aged 10-12 years provided both urine and stool samples. The samples were examined for the presence of eggs using the urine sedimentation technique for S. haematobium and the Kato Katz technique for STHs. Pearson's chi-square test was used to calculate the association and Spearman's rank correlation was used for the correlation analysis. There was a highly significant correlation between S. haematobium and STHs at a school level (Spearman's correlation coefficient =0.93; p<0.001). The prevalences were found to be 36.9% and 38.8% for S. haematobium and STHs, respectively. A significant association was found between S. haematobium and STHs (odds ratio =2.05; confidence interval =1.58-2.93; p<0.001). Indirect indicators of urogenital schistosomiasis (e.g. water contact and haematuria) were significantly associated with A. lumbricoides and T. trichiura infection. We have demonstrated a highly significant correlation and overall association between urogenital schistosomiasis and A. lumbricoides and T. trichiura. We cautiously suggest that all S. haematobium endemic areas should be treated for STH infections. [ABSTRACT FROM AUTHOR]