Yu J M, de Vlas S J, Yuan H C, Gryseels B
Department of Epidemiology, Shanghai Medical University, People's Republic of China.
Am J Trop Med Hyg. 1998 Sep;59(3):370-5. doi: 10.4269/ajtmh.1998.59.370.
Variations in fecal Schistosoma japonicum egg counts were studied in ZhuXi administrative village, JiangXi Province, China. Population stool examinations were collected with duplicate, standard, 41.5-mg Kato-Katz thick smears on seven consecutive days for 570 individuals from two natural (individual) villages: village I with high endemicity and village II with low endemicity. The proportion of individuals with at least one positive count increased from 42.4% after a single measurement to 68.3% after seven measurements in village I (n = 356), and from 17.0% to 36.0% in village II (n = 214), respectively. This demonstrates a very high variation in repeated S. japonicum egg counts and a considerable lack of sensitivity of the Kato-Katz technique; light and moderate infections are especially missed with a single or a few measurements. The observed day-to-day variation in individual egg counts is highly aggregated (variance higher than the mean) and suggestive of a negative binomial distribution. For five individuals on three days, repeated sampling from different locations of a stool specimen shows a clear trend with egg counts decreasing from the beginning of the stool to the end and from the outside layer to the center. Ten multiple samples from a particular subsection (10-30 g) of a stool specimen for 44 positive individuals still showed aggregation in egg counts, particularly for high intensities of infection. This means that the aggregation in repeated daily S. japonicum egg counts cannot be explained alone by a specific day-to-day component and variation in the concentration of eggs at different locations in the stool. There also exists clustering of eggs within parts of the stool.
在中国江西省珠溪行政村对日本血吸虫粪便虫卵计数的变化情况进行了研究。对来自两个自然（个体）村庄的570人连续7天收集粪便样本，采用标准的41.5毫克加藤厚涂片法进行双份检测：I村为高流行村，II村为低流行村。I村（n = 356）至少有一次阳性计数的个体比例从单次检测后的42.4%增加到7次检测后的68.3%，II村（n = 214）则分别从17.0%增加到36.0%。这表明日本血吸虫虫卵重复计数存在很大差异，加藤厚涂片法的敏感性相当不足；单次或几次检测尤其容易漏检轻度和中度感染。观察到的个体虫卵计数的每日变化高度聚集（方差高于均值），提示呈负二项分布。对5名个体在3天内从粪便样本的不同部位重复采样显示，虫卵计数从粪便前端到末端、从外层到中心呈明显下降趋势。对44名阳性个体的粪便样本特定小节（10 - 30克）进行的10次重复采样仍显示虫卵计数聚集，尤其是高强度感染情况。这意味着日本血吸虫虫卵每日重复计数中的聚集现象不能仅由特定的每日因素和粪便中不同位置虫卵浓度的变化来解释。粪便各部分内也存在虫卵聚集现象。
