RESUMO
Storage of stools for the detection of soil-transmitted helminths (STH) remains challenging for the molecular diagnostic testing of STH infections. This study aimed to overcome this challenge by assessing the capacity of Whatman filter papers to store stools for the molecular detection of STHs. Stool samples were collected from school-aged children of soil-transmitted helminthiasis endemic areas of Cameroon and then, analysed using Kato Katz technique. For this study, 128 and 40 stool samples respectively with and without STH eggs were analysed. From each sample, 10, 20, 40 and 80 mg of stool were weighted and spread on 6 grades of Whatman filter papers that were stored at room temperature from one to ten weeks. DNA was extracted from spread stool using CTAB based-method. The amount of stool to spread on filter papers and the grade of filter paper offering good storage were determined by amplifying specific DNA fragments of Ascaris lumbricoides. The capacity of filter papers to store stool samples for several weeks before the molecular detection of STH species was assessed by amplifying specific DNA fragments of different STHs. The amplification rates of A. lumbricoides were significantly higher (P < 0.0001) for 10 and 20 mg of stored stools. Stools spread on Whatman paper grade 2 yielded the highest amplification rate of 100% for A. lumbricoides, T. trichiura and hookworm. PCR revealed STH infections in all the 128 spread stools carrying STH eggs. It also revealed Necator americanus and Ancylostoma duodenale respectively in 10 and 13 of 15 spread stools contained hookworm eggs. PCR confirmed the co-infections of these hookworm species as well as that of A. lumbricoides and Trichuris trichiura in 7 spread stools. Out of 40 stools without STH eggs, PCR revealed that 5 (12.5%) and 9 (22.5%) had respectively A. lumbricoides and T. trichiura infections. The amplification rate of each STH species was 100% from one to 8 weeks and decreased to 86.7% after 10 weeks of storage. This study highlighted the capacity of filter papers to store stools for the molecular detection of STHs. Storing stools on these papers will enable to monitor and evaluate control programs and ensure post-elimination surveillance.
