Schär F, Hattendorf J, Khieu V, Muth S, Char M C, Marti H P, Odermatt P
Department of Epidemiology and Public Health, Swiss Tropical and Public Health Institute, Basel, Switzerland.
National Center for Parasitology, Entomology and Malaria Control, Ministry of Health, Cambodia.
Parasitology. 2014 Jun;141(7):892-7. doi: 10.1017/S0031182013002345. Epub 2014 Feb 17.
The variability of larval excretion impedes the parasitological diagnosis of Strongyloides stercoralis in infected individuals. We assessed the number of larvae excreted per gram (LPG) stool in 219 samples from 38 infected individuals over 7 consecutive days before and in 470 samples from 44 persons for 21 consecutive days after ivermectin treatment (200 μg kg-1 BW). The diagnostic sensitivity of a single stool sample was about 75% for individuals with low-intensity infections (⩽1 LPG) and increased to 95% for those with high-intensity infections (⩾10 LPG). Doubling the number of samples examined per person increased sensitivity to more than 95%, even for low-intensity infections. There was no indication of a cyclic excretion of larvae. After treatment, all individuals stopped excreting larvae within 3 days. Larvae were not detected during any of the following 18 days (total 388 Baermann and 388 Koga Agar tests). Two stool samples, collected on consecutive days, are recommended in settings where low or heterogeneous infection intensities are likely. In this way, taking into account the possible biological variability in excretion, the efficacy of ivermectin treatment can be assessed as soon as 4 days after treatment.
幼虫排泄的变异性妨碍了对感染个体中粪类圆线虫的寄生虫学诊断。我们评估了38名感染个体在伊维菌素治疗（200μg/kg体重）前连续7天的219份粪便样本以及44名个体在治疗后连续21天的470份粪便样本中每克粪便排出的幼虫数量（LPG）。对于低强度感染（≤1 LPG）的个体，单个粪便样本的诊断敏感性约为75%，而对于高强度感染（≥10 LPG）的个体，敏感性则提高到95%。即使对于低强度感染，将每人检查的样本数量翻倍也会使敏感性提高到95%以上。没有迹象表明幼虫存在周期性排泄。治疗后，所有个体在3天内停止排出幼虫。在接下来的18天内（共388次贝尔曼试验和388次小田琼脂试验）均未检测到幼虫。在感染强度可能较低或不均匀的情况下，建议连续两天采集两份粪便样本。通过这种方式，考虑到排泄中可能存在的生物学变异性，在治疗后4天即可评估伊维菌素治疗的效果。
