Comparison of individual and pooled stool samples for the assessment of schistosoma mansoni and soiltransmitted helminth infections intensity by kato katz technique in jimma zone, south-west, Ethiopia

Abstract

BACKGROUND: Schistosomiasis and soil-transmitted helminthiasis (STHs) are the most pervasive types of parasitic infections in the world. Schistosomiasis or bilharziasis is a tropical disease caused by worms of the genus Schistosoma. More than 207 million people are suffering from schistosomiasis and nearly 800 million people are at risk of infection globally and leading to the loss of between 1.7 and 4.5 million disability adjusted life years (DALYs). Schistosomiasis is a public health problem, and its control is advocated by the World Health Organization (WHO) and other international agencies with the strategy based on preventive chemotherapy. Moreover health strategy for the success of effective parasitic disease control programs demand knowledge of magnitude of the disease. Rapid, cost effective and accurate assessment of the prevalence and intensity of infections are lacking. Therefore, pooling of stool samples may be the new possible alternative to assess infection intensity of schistosomiasis in comparison to individual stool examination. In the present study we evaluated the pooling of stool for the assessment of intensity of Schistosoma mansoni and STHs (Ascaris lumbricoides, Trichuris trichiura and hookworms) infections. In addition, we assessed the time required to screen individual and pooled stool samples. METHODS AND MATERIALS: A cross-sectional school based survey was conducted in 360 children aged between 5 to 18 years from six schools in Jimma Zone (South-west Ethiopia) from February to May 2014. In both individual and pooled stool samples (pools sizes of 5, 10 and 20) the faecal egg counts (FEC) was determined by means of eggs per gram of stool (epg) using the KatoKatz technique. The agreement between means fecal egg count for individual samples and the pooled samples were evaluated by the Spearman rank correlation coefficient for S. mansoni and STHs infections. The confidence interval and the mean difference in FEC were calculated at 95%. The data were analyzed by SPSS window version 20.0. RESULTS: Out of 360 study participants, 218 (60.5%) of them were found positive for any helminthic (S. mansoni and the three STHs) infection. The prevalence rate of S. mansoni and STHs infection were 25.3 % (11.7% in females and 13.6% in males) and 48.3% (22.8% in females and 25.5% in males) respectively. T. trichiura was the predominant species (30.6 %), followed by hookworms (21.4%) and A. lumbricoides (18.1%) among STHs infection respectively.The arithmetic mean FEC was 2,596.3 EPG, 126.0 EPG, 47.3 EPG and 40.7 EPG for A. lumbricoides, T. trichiura, S. mansoni and hookworms, respectively. Except for hookworms, there was a significant correlation (coefficient = 0.53-0.95) between the mean of individual FECs and the FECs of pooled samples for A. lumbricoides, T. trichiura and S. mansoni, regardless of the pool size. There was no significant difference in FECs between the examination of individual and pooled stool samples, except for hookworms. For these STHs, pools of 10 resulted in a significant lower FECs. The total time to determine individual FECs for 360 samples was 65 hours and 5 minutes, while a pools of 20 only 12 hours and 42 minutes. CONCLUSIONS AND RECOMMENDATIONS: S. mansoni was moderately prevalent in the study areas, while almost half of the study population harbors any STHs. Pooling of stool samples holds promising for a rapid assessment of the infections intensity of S. mansoni and STHs by KatoKatz technique. Employing pooling strategies can reduce time of examination by up to 87% compared to examining individual samples. Preventive chemotherapy and health education should be implemented to reduce the burden of schistosomiasis and STHs in the study areas. Moreover, further research is required to determine how pooling of stool samples applicable for this parasitic infections with different pools size, samples size, diagnostic technique and prevalence study.