Improved latrines minimally impact Schistosoma mekongi transmission in Mekong islands

Abstract

Schistosoma mekongi and other intestinal helminth infections remain public health concerns in Lao People's Democratic Republic, especially in remote areas where access to sanitation is limited.

We performed an experimental study in four villages where latrine construction was coupled with two rounds of mass drug administration (MDA) with praziquantel and albendazole, and compared with two control villages that only received two rounds of MDA. The prevalence of helminth infections before (baseline) and after (follow-up) intervention were compared. Additionally, the prevalence in intervention and control villages were compared 12 months post-intervention. Kato–Katz, formalin-ethyl acetate concentration and Baermann techniques were employed to assess helminth infections.

We found infection prevalence of S. mekongi in the intervention and control villages was 28.6% and 1.8%, respectively. The prevalences of other helminth infections were as follows: Opisthorchis viverrini, 79.5% and 71.8%; hookworm, 48.8% and 65.6%; and Strongyloides stercoralis, 43.1% and 38.3%. Other helminth species were detected in less than 5% of the study participants. Latrine intervention coupled with two rounds of MDA in the intervention villages reduced the prevalence of S. mekongi infection by 6.0% (from 28.6% to 22.6%; P < 0.001), O. viverrini infection by 11.3% (from 79.5% to 68.2%; P < 0.001), hookworm infection by 22.6% (from 48.8% to 26.2%; P < 0.001), and S. stercoralis infection by 12.0% (from 43.1% to 31.1%; P < 0.001). The observed reductions were not significantly different when compared to the control villages, where only two rounds of MDA were implemented (P > 0.05). Study participants in both groups commonly engaged in behaviours such as open defecation, bathing in the Mekong River, consuming raw or undercooked fish dishes and walking barefoot. These practices and behaviours are associated with helminth infections. Concluding, this study showed only a marginal impact associated with latrine use in intervention communities. There is a need for longer term studies with integrated interventions, such as effective health education to foster behavioural changes related to open defecation, raw or undercooked food consumption, wearing protected footwear outdoors, and personal hygiene.