Kloos H, Fulford A J, Butterworth A E, Sturrock R F, Ouma J H, Kariuki H C, Thiongo F W, Dalton P R, Klumpp R K
Department of Epidemiology and Biostatistics, University of California, San Francisco, USA.
Soc Sci Med. 1997 Apr;44(7):949-68. doi: 10.1016/s0277-9536(96)00218-3.
This paper presents the results of microgeographical studies of human water contact behavior and Schistosoma mansoni transmission levels and intensity of infection in four rural areas in Machakos District, Kenya. The relationship between intensity of infection (geometric mean egg counts) in 3502 persons aggregated in 120 household clusters and eight independent variables was investigated using straight and stepwise linear regression and mapping techniques. Results indicate that the two water contact variables, mean frequency per person and mean duration per person, as well as mean number of sites used per person, a transmission index and mean distance to the most frequently used site were the strongest predictors of geometric mean egg counts. All three distance variables were usually negatively associated with infection although intensity of infection and water contact declined relatively slowly with distance from the streams. This pattern appears to be owing to a combination of the relatively short distances, a general lack of safe alternative water sources and the use of more distant water contact sites both inside and outside the study area during periods of drought. The study of snail-to-man transmission identified number of infected snails as the major transmission variable and number of contacts as the major predictor variable. Mapping of total egg counts at the household cluster level and total number of infected snails revealed spatial association with transmission sites. All results varied considerably between study areas, owing to differences in exposure levels, transmission patterns and environmental factors. Findings are discussed in relation to the epidemiology and control of schistosomiasis and suggestions are made for further spatial studies.
本文介绍了在肯尼亚马查科斯区四个农村地区开展的关于人类与水接触行为、曼氏血吸虫传播水平及感染强度的微观地理研究结果。运用直线和逐步线性回归以及绘图技术，对120个家庭群组中3502人的感染强度（虫卵计数几何均值）与八个独立变量之间的关系进行了研究。结果表明，两个人与水接触变量，即每人平均接触频率和每人平均接触时长，以及每人使用的地点平均数量、一个传播指数和到最常使用地点的平均距离，是虫卵计数几何均值的最强预测因素。尽管感染强度和与水接触情况随离溪流距离的增加而相对缓慢下降，但所有三个距离变量通常与感染呈负相关。这种模式似乎是由于距离相对较短、普遍缺乏安全的替代水源，以及在干旱时期研究区域内外都使用距离更远的与水接触地点等多种因素共同作用的结果。对钉螺到人的传播研究确定，感染钉螺的数量是主要传播变量，接触次数是主要预测变量。在家庭群组层面绘制的总虫卵计数和感染钉螺总数图显示，与传播地点存在空间关联。由于暴露水平、传播模式和环境因素的差异，所有结果在不同研究区域之间有很大差异。结合血吸虫病的流行病学和防控对研究结果进行了讨论，并对进一步的空间研究提出了建议。
