Mabaso M L H, Appleton C C, Hughes J C, Gouws E
School of Life and Environmental Sciences, University of Natal, Durban, South Africa.
Trop Med Int Health. 2004 Apr;9(4):471-6. doi: 10.1111/j.1365-3156.2004.01216.x.
This study extended the association between hookworm transmission in KwaZulu-Natal and the sandy coastal plain by investigating the parasite's occurrence in isolated areas of sandy soils further inland. A school-based prevalence survey was carried out in selected inland sandy areas and in surrounding areas dominated by clay soils within a narrow altitudinal range of between 500 and 700 m to reduce the effect of altitude on climate-related factors (rainfall and temperature). Sandy areas situated on the coastal plain were included in the analysis for comparative purposes. Soil samples (0-50 mm depth) were collected from each locality to assess their nematode loadings and to analyse selected physical and chemical properties. Significant differences were found between the moderate prevalence of hookworm infection among children living in inland areas with sandy soils (17.3%) and the low prevalence in surrounding non-sandy areas (5.3%, P < 0.001), and between infection among children living in all inland areas (9.3%) and the high prevalence on the coastal plain (62.5%, P < 0.001). Amounts of fine and medium sand were highest in both the coastal plain soils and in inland sandy areas and these fractions showed a significant positive correlation with hookworm prevalence and nematode loadings. Clay, coarse sand and organic matter contents were highest in surrounding non-sandy soils and showed a significant negative correlation with the nematode variables. No statistically significant correlations were found with soil pH at study localities. We conclude that properties of inland sandy soils, particularly particle size distribution, correlate well with hookworm prevalence and nematode loadings and therefore provide a more suitable habitat for nematodes than surrounding non-sandy areas. These results suggest that particle size distribution of sand fractions, organic matter and clay content in the soil influence the survival of hookworm larvae and hence the parasite's transmission.
本研究通过调查寄生虫在更内陆的沙质土壤孤立区域的出现情况，扩展了夸祖鲁 - 纳塔尔省钩虫传播与 sandy 沿海平原之间的关联。在选定的内陆沙质地区以及海拔 500 至 700 米狭窄范围内以黏土为主的周边地区开展了一项基于学校的患病率调查，以减少海拔对气候相关因素（降雨和温度）的影响。出于比较目的，将位于沿海平原的沙质地区纳入分析。从每个地点采集土壤样本（0 - 50 毫米深度），以评估其线虫负荷并分析选定的物理和化学性质。在内陆沙质土壤地区生活的儿童中钩虫感染的中度患病率（17.3%）与周边非沙质地区的低患病率（5.3%，P < 0.001）之间，以及所有内陆地区儿童的感染率（9.3%）与沿海平原的高患病率（62.5%，P < 0.001）之间均发现了显著差异。沿海平原土壤和内陆沙质地区的细沙和中沙含量最高，这些组分与钩虫患病率和线虫负荷呈显著正相关。黏土、粗沙和有机质含量在周边非沙质土壤中最高，并且与线虫变量呈显著负相关。在研究地点未发现与土壤 pH 的统计学显著相关性。我们得出结论，内陆沙质土壤的性质，特别是颗粒大小分布，与钩虫患病率和线虫负荷密切相关，因此比周边非沙质地区为线虫提供了更适宜的栖息地。这些结果表明，土壤中沙粒级分的颗粒大小分布、有机质和黏土含量会影响钩虫幼虫的存活，进而影响寄生虫的传播。
