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Soil Science

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Browsing Soil Science by Author "Appleton, Christopher Charles."

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    Environmental contamination, prevalence and other risk factors for geohelminth infection in three informal settlements in Durban, South Africa.
    (2011) Rajcoomar, Kelleen.; Appleton, Christopher Charles.; Mukaratirwa, Samson.
    The effect of different types of sanitation facilities on soil contamination with geohelminth eggs and the associated risk factors were assessed in three informal settlements in Durban, South Africa. Adult members of 30 households in each settlement were interviewed to determine their knowledge, attitudes and perceptions on risk factors associated with geohelminth transmission. Two hundred soil samples were collected in each study settlement from areas considered potential sources of infection such as houses, pathways, sanitation facilities and washing areas. Of the total 600 soil samples collected, 190 (32%) were positive for geohelminth eggs with the eggs of Ascaris lumbricoides, Trichuris trichiura and Taenia spp. being recovered. Quarry Road West, where open defaecation was the most common (80%), sanitation coverage the lowest (11%) and lack of knowledge on geohelminth transmission high (97%), showed the highest levels of soil contamination (mean = 102.55eggs/100g). Stool samples were also collected from 135 children aged 1-16 years living in the three study areas. Children were found to be infected with A. lumbricoides and T. trichiura with prevalences of 33.4 and 6.5%, respectively and corresponding geometric mean intensities of 5.6 and 0.87eggs/g faeces. Some children (9.6%) also harboured dual infections. No hookworm or tapeworm infections were recorded. The results show a direct link between high levels of soil contamination and increased prevalence and infection rates. Indiscriminate defaecation by community members is recognised as the main contributing factor of geohelminth eggs in soil. The type and the number of toilets provided to a community greatly influence the success of a sanitation facility. In order to effectively control geohelminth transmission, health education and antihelminthic treatment need to accompany sanitation programmes in these areas.
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    Environmental factors influencing the distribution hookworm infection in KwaZulu-Natal, South Africa [sic].
    (1998) Mabaso, Musawenkosi.; Appleton, Christopher Charles.; Hughes, Jeffrey Colin.
    The aim of this study was to investigate the occurrence of the soil transmitted parasitic nematode Necator americanus ("Old World" hookworm) in soils of different texture in KwaZulu-Natal. The key questions being asked were: (i) Is hookworm infection in KwaZulu-Natal confined to the coastal plain? (ii) Is there any association between hookworm prevalence and the different soil types in the province? (iii) Since several examples exist in the province of soil types on which hookworm is transmitted on the coastal plain, occurring inland, what is the status of infection in communities situated in these areas? (iv) What properties of soil are important in the transmission ecology of hookworm larvae? All available hookworm prevalence data of KwaZulu-Natal were mapped on Land Type maps of the province (Land Type Survey Staff, 1986). Several additional surveys were carried out to supplement this database. Faecal egg counts were obtained by the Formal-Ether Concentration Method and positive infections were confirmed as N. americanus by larval morphology after coproculture using the Harada-Mori Technique. Univariate analysis was carried out for significant associations between hookworm prevalence, altitude, climatic variables (rainfall and temperature) and soil type. The results showed that areas ≤ 150m above sea level (i.e. the coastal plain) support high prevalences (x ‾ = 45 %), and are characterised by low-clay textured soils, warm temperatures and relatively high rainfall. Areas > 150 m (i.e. inland) have low hookworm prevalences (x ‾ = 6 %), and are characterised by high-clay textured soils, cool temperatures and moderate rainfall. Hookworm prevalence also decreased southwards as climatic conditions (rainfall and temperature) become unfavourable, and the coastal plain also narrows in this direction. Multivariate analysis was done to determine which environmental factors combine best to provide favourable conditions for hookworm transmission. From the variables used, prevalence of infection was most significantly correlated with the mean daily minimum temperature for January followed by the mean number of rainy days for January. This points to the importance of summer conditions in the transmission of hookworm infection in KwaZulu-Natal. Moderate hookworm prevalences (x ‾ = 17.3 %) were found in the inland sandy areas, dropping to low prevalences (x ‾ = 5.3 %) in the surrounding non-sandy areas. The intensity-related data could not be significantly correlated with the environmental variables used in this study. The Spearman Correlation Coefficient was used to test for relationships between hookworm prevalence and soil variables. In the results, only the fine and medium sand fractions showed positive correlations with hookworm prevalence. Clay showed a significant negative correlation with hookworm prevalence. No significant correlations were found between soil pH or its organic matter content and hookworm prevalence. Age and sex related infection data could not be drawn into the analysis due to the small sample size of study localities.