Mabaso M L H, Appleton C C, Hughes J C, Gouws E
National Malaria Research Programme, Durban, South Africa School of Life & Environmental Sciences, University of Natal, Durban, South Africa.
Trop Med Int Health. 2003 Aug;8(8):722-7. doi: 10.1046/j.1365-3156.2003.01086.x.
We investigated environmental factors influencing the distribution of hookworm infection in KwaZulu-Natal, South Africa. Prevalence data were sourced from previous studies and additional surveys carried out to supplement the database. When geo-referenced the data revealed that higher prevalences are limited to areas below 150 m above sea level, and low prevalences to areas above this altitude. Using univariate analysis we investigated the differences in environmental factors in the two areas. The relationship between hookworm prevalence, altitude and climate-derived variables was assessed using Pearson correlation coefficient, and that of soil type using the t-test. Multivariate analysis was used to determine environmental factors that combine best to provide favourable conditions for hookworm distribution. The results revealed that areas <or=150 m above sea level, i.e. the coastal plain, supported high prevalences (x = 45, n = 51), and were characterized by sandy soils with a clay content of less than 15%, warm temperatures and relatively high rainfall. Areas >150 m above sea level, i.e. inland, supported low mean hookworm prevalences (x = 6, n = 21), and were characterized by soils with a clay content of more than 45%, variable temperatures and moderate rainfall. Hookworm prevalence also decreased southwards as temperatures became slightly cooler, rainfall remained more-or-less constant and the coastal plain narrowed. In the multivariate model prevalence was most significantly correlated with the mean daily minimum temperature for January followed by the mean number of rainy days for January. This indicates the importance of summer conditions in the transmission of hookworm infection in KwaZulu-Natal and suggests that transmission may be seasonal.
我们调查了影响南非夸祖鲁 - 纳塔尔省钩虫感染分布的环境因素。患病率数据来源于以往的研究以及为补充数据库而开展的额外调查。对数据进行地理定位后发现，较高的患病率仅限于海拔150米以下的地区，而较低的患病率则出现在海拔高于此高度的地区。我们使用单变量分析研究了这两个地区环境因素的差异。使用皮尔逊相关系数评估钩虫患病率、海拔与气候衍生变量之间的关系，使用t检验评估土壤类型与钩虫患病率之间的关系。采用多变量分析来确定最能结合起来为钩虫分布提供有利条件的环境因素。结果显示，海拔≤150米的地区，即沿海平原，钩虫患病率较高（x = 45，n = 51），其特征是砂土，粘土含量低于15%，温度温暖且降雨相对较多。海拔>150米的地区，即内陆地区，钩虫平均患病率较低（x = 6，n = 21），其特征是粘土含量超过45%的土壤，温度多变且降雨适中。随着温度略有下降、降雨量大致保持不变且沿海平原变窄，钩虫患病率也向南降低。在多变量模型中，患病率与1月份平均每日最低温度最显著相关，其次是1月份的平均雨天数。这表明夏季条件在夸祖鲁 - 纳塔尔省钩虫感染传播中的重要性，并表明传播可能具有季节性。
