Investigating cement-based surfaces as a sustainable flooring solution to improve Ascaris Suum egg removal and inactivation in low-resource settings

Soil-transmitted helminths, like Ascaris lumbricoides, are significant contributors to disease burden in low- and middle-income countries (LMICs). Infections are associated with morbidity and mortality in children and are often transmitted through eggs in fecally contaminated soil. Interventions, like replacing household soil floors with cement-based alternatives, may reduce exposure to A. lumbricoides eggs, but there are currently no estimates on the removal or survival of Ascaris species eggs on cement-based surfaces. This study addresses that knowledge gap by evaluating the removal of Ascaris suum eggs from mopping and the survival of A. suum eggs on two cement-based mixes: an traditional mortar and a mortar with fly ash, which provides a more sustainable alternative to the traditional mortar mix. We assessed egg survival at two temperatures representing the dry (15°C) and wet (34°C) seasons in Bangladesh using two different egg enumeration methods. After mopping, a mean of 95.6% (SD = 4.0%) of viable eggs were removed from surfaces, with no significant differences between cement-based mixes (p = 0.51). The mean first-order decay rate constants (k) of A. suum eggs across all conditions was 0.029 day-1 (SD = 0.074 day-1). Values of k were similar between mix designs (p = 0.62) but varied significantly between temperatures (p = 4.2x10-25) and egg enumeration methods (p = 2.4x10-8). The k values were greater at 34°C compared to at 15°C, where they showed no significant inactivation. Our k values were comparable to those reported previously for different matrices, indicating comparable inactivation of Ascaris species eggs on cement-based surfaces compared to liquid and semi-solid matrices. These results provide some of the first estimates of removal efficiencies and decay rate constants in realistic environmental conditions for Ascaris species on surfaces while supporting the use of mortar mix designs with fly ash in interventions to reduce Ascaris species transmission in rural LMIC households.Author summary: Soil-transmitted helminths, like Ascaris lumbricoides, are parasites that are major contributors to disease in children and women of childbearing age in low- and middle-income countries. Interventions, like replacing soil floors in households with cement-based flooring, may reduce exposure to A. lumbricoides eggs which cause infections, but there is little information on how or why these interventions may be effective. This study investigates the effectiveness of simple cleaning methods, like mopping, in removing Ascaris suum eggs from cement-based surfaces and explores how long these eggs can survive on these surfaces under different environmental conditions. We tested two types of cement-based surfaces, a traditional cement-based mortar mix, and a more sustainable cement-based mortar mix, and found that mopping removed 95.6% (SD = 4.0%) of A. suum eggs, with no differences between cement mixes. Experiments simulating wet and dry seasonal conditions showed that A. suum eggs survive longer in cooler environments, again with no differences between cement mixes. These findings provide important insights into the role of cement-based flooring in interrupting disease transmission and suggest sustainable cement-based mortar mixes are a feasible alternative to traditional cement-based mortar mixes.