Barda Beatrice, Albonico Marco, Ianniello Davide, Ame Shaali M, Keiser Jennifer, Speich Benjamin, Rinaldi Laura, Cringoli Giuseppe, Burioni Roberto, Montresor Antonio, Utzinger Jürg
Department of Medical Parasitology and Infection Biology, Swiss Tropical and Public Health Institute, Basel, Switzerland; University of Basel, Basel, Switzerland.
Ivo de Carneri Foundation, Milano, Italy.
PLoS Negl Trop Dis. 2015 Apr 7;9(4):e0003698. doi: 10.1371/journal.pntd.0003698. eCollection 2015 Apr.
Kato-Katz is a widely used method for the diagnosis of soil-transmitted helminth infection. Fecal samples cannot be preserved, and hence, should be processed on the day of collection and examined under a microscope within 60 min of slide preparation. Mini-FLOTAC is a technique that allows examining fixed fecal samples. We assessed the performance of Mini-FLOTAC using formalin-fixed stool samples compared to Kato-Katz and determined the dynamics of prevalence and intensity estimates of soil-transmitted helminth infection over a 31-day time period.
The study was carried out in late 2013 on Pemba Island, Tanzania. Forty-one children were enrolled and stool samples were subjected on the day of collection to a single Kato-Katz thick smear and Mini-FLOTAC examination; 12 aliquots of stool were fixed in 5% formalin and subsequently examined by Mini-FLOTAC up to 31 days after collection.
The combined results from Kato-Katz and Mini-FLOTAC revealed that 100% of children were positive for Trichuris trichiura, 85% for Ascaris lumbricoides, and 54% for hookworm. Kato-Katz and Mini-FLOTAC techniques found similar prevalence estimates for A. lumbricoides (85% versus 76%), T. trichiura (98% versus 100%), and hookworm (42% versus 51%). The mean eggs per gram of stool (EPG) according to Kato-Katz and Mini-FLOTAC was 12,075 and 11,679 for A. lumbricoides, 1,074 and 1,592 for T. trichiura, and 255 and 220 for hookworm, respectively. The mean EPG from day 1 to 31 of fixation was stable for A. lumbricoides and T. trichiura, but gradually declined for hookworm, starting at day 15.
CONCLUSIONS/SIGNIFICANCE: The findings of our study suggest that for a qualitative diagnosis of soil-transmitted helminth infection, stool samples can be fixed in 5% formalin for at least 30 days. However, for an accurate quantitative diagnosis of hookworm, we suggest a limit of 15 days of preservation. Our results have direct implication for integrating soil-transmitted helminthiasis into transmission assessment surveys for lymphatic filariasis.
加藤厚涂片法是一种广泛用于诊断土源性蠕虫感染的方法。粪便样本不能保存，因此应在采集当天进行处理，并在涂片制备后60分钟内在显微镜下检查。微型浮游分析法是一种可用于检查固定粪便样本的技术。我们将使用福尔马林固定粪便样本的微型浮游分析法与加藤厚涂片法的性能进行了评估，并确定了31天时间内土源性蠕虫感染患病率和感染强度估计值的动态变化。
该研究于2013年末在坦桑尼亚的奔巴岛开展。招募了41名儿童，在采集粪便样本当天对其进行一次加藤厚涂片法和微型浮游分析法检查；将12份粪便等分样本固定于5%福尔马林中，随后在采集后长达31天的时间里通过微型浮游分析法进行检查。
加藤厚涂片法和微型浮游分析法的综合结果显示，100%的儿童鞭虫检测呈阳性，85%的儿童蛔虫检测呈阳性，54%的儿童钩虫检测呈阳性。加藤厚涂片法和微型浮游分析法对蛔虫（85%对76%）、鞭虫（98%对100%）和钩虫（42%对51%）的患病率估计相似。根据加藤厚涂片法和微型浮游分析法，蛔虫每克粪便中的虫卵数（EPG）平均分别为12,075和11,679，鞭虫为1,074和1,592，钩虫为255和220。从固定第1天到第31天，蛔虫和鞭虫的平均EPG稳定，但钩虫从第15天开始逐渐下降。
结论/意义：我们的研究结果表明，对于土源性蠕虫感染的定性诊断，粪便样本可用5%福尔马林固定至少30天。然而，对于钩虫的准确定量诊断，我们建议保存期限限制在15天。我们的结果对将土源性蠕虫病纳入淋巴丝虫病传播评估调查具有直接意义。
