Demographic Factors Driving Schistosomiasis and Soil-Transmitted Helminthiases in Milola Ward, Lindi District, Tanzania: A Useful Guide for Launching Intervention Programmes

Abstract

Background: Current information on the distribution of and risk factors for schistosomiasis and soil-transmitted helminthiases is scarce for most areas of southern Tanzania, including Milola Ward in Lindi District. This study was initiated to establish the status of these infections in Milola Ward and to assess how they vary with demographic factors.

Methods: From September to October 2014, 2 sets of stool and urine samples were collected from residents of Milola Ward. The Kato–Katz technique was used to examine stool samples for faecal-borne parasites, and the filtration technique was used to examine urine for urinary schistosomes. A total of 195 individuals aged 5 to 90 years were enrolled in the study; 190 (97%) participants submitted adequate urine samples, of whom 107 (56%) were female and 83 (43%) were male. Of the 195 participants who took part in the initial sampling exercise, 158 (81%) provided adequate stool samples; 121 (77%) of these were adults, and the rest (n=37, 23%) were children. Only 53 urine and 26 faecal samples were obtained in the second round of sampling, and due to marked inconsistencies, these have been excluded from the analysis. Mean parasite abundance was analysed for its association with demographic factors, such as age and sex.

Results: Three varieties of parasite were detected, namely, Schistosoma haematobium in 44 (23%) of 190 urine samples, hookworms in 12 (8%) of 158 stool samples, and Trichuris trichiura in 6 (4%) of 158 stool samples. The difference in S. haematobium prevalence between male and female participants (27 of 107 females, 25% vs 17 of 83 males, 20%) was not statistically significant (Kruskal–Wallis test, P=.47). Linear regression analysis of S. haematobium infection with age showed a significant association, with children having higher infection intensities than adults (P<.001). S. haematobium prevalence and intensity did not vary significantly between villages (intensity [Kruskal–Wallis test], P=.95; prevalence, P=.88).

Discussion: These data confirm that in this setting, the mean age of peak helminthiasis prevalence decreases as transmission pressure increases, with non-school children below 18 years old being most at risk of acquiring parasitic infections. This was the first baseline survey of parasitic infections in Milola Ward, so the results will be crucial for guiding control efforts against parasitic diseases in the area.