Elimination of Schistosomiasis Mekongi from Endemic Areas in Cambodia and the Lao People’s Democratic Republic: Current Status and Plans

Abstract

The areas endemic for schistosomiasis in the Lao People's Democratic Republic and in Cambodia were first reported 50 and 60 years ago, respectively. However, the causative parasite Schistosoma mekongi was not recognized as a separate species until 1978. The infection is distributed along a limited part of the Mekong River, regulated by the focal distribution of the intermediate snail host Neotricula aperta. Although more sensitive diagnostics imply a higher figure, the current use of stool examinations suggests that only about 1500 people are presently infected. This well-characterized setting should offer an exemplary potential for the elimination of the disease from its endemic areas; yet, the local topography, reservoir animals, and a dearth of safe water sources make transmission control a challenge. Control activities based on mass drug administration resulted in strong advances, and prevalence was reduced to less than 5% according to stool microscopy. Even so, transmission continues unabated, and the true number of infected people could be as much as 10 times higher than reported. On-going control activities are discussed together with plans for the future.

Core components, concepts and strategies for parasitic and vector-borne disease elimination with a focus on schistosomiasis: A landscape analysis

“…Key informants emphasized that community involvement in the planning and implementation of interventions is crucial to ensure uptake, acceptance and sustainability of WASH interventions. Successful examples of comprehensive community-led MDA combined with community-led WASH (CL-WASH) interventions for schistosomiasis control in Cambodia and Lao PDR have been published [ 24 , 38 ].…”

“…Several key informants pointed out that early childhood education has proven effective in adapting and improving WASH behavior and is applied for trachoma and soil-transmitted helminth (STH) control and prevention through habit formation. Community participation was identified by key informants and in the literature as crucial to maximize acceptance, gain a sense of ownership and empowerment and achieve sustainability of interventions and activities including vector control, WASH, surveillance, treatment, health education and behavior change communication in programmes targeting malaria, dengue, schistosomiasis, Guinea worm and other parasitic and vector-borne diseases [ 11 , 24 , 43 , 46 , 53 , 60 – 62 , 72 – 76 ]. Caregivers, social groups, religious or community leaders, teachers and health staff should be engaged in control activities, intervention planning and design of tools [ 77 ].…”

“…China [ 22 , 26 , 27 , 29 , 39 , 42 , 95 – 97 ]. The value of integrated One Health approaches has been described in the context of Schistosoma mekongi elimination efforts in Lao PDR and Cambodia [ 24 ]. Other Asian countries and Puerto Rico reported similar experiences [ 37 , 38 , 90 ].…”

“…The rationale for integrated schistosomiasis control and elimination efforts to advance towards interruption of transmission as opposed to the current approach, mainly relying on MDA for elimination of schistosomiasis as a public health problem, has been discussed repeatedly for non-African settings [ 11 , 21 , 24 , 36 , 38 , 55 , 63 , 90 , 115 , 116 ], but also with reference to Nigeria [ 75 ], Zanzibar [ 117 ] and Egypt [ 105 ]. Low acceptance of MDA, vector control or WASH interventions [ 103 , 116 ] as well as insufficient resources, weak health systems and lack of coordination are a reality in many programs [ 11 , 21 , 38 , 55 , 63 , 66 , 95 , 97 , 115 , 116 ].…”

Vaccination or mass drug administration against schistosomiasis: a hypothetical cost-effectiveness modelling comparison

“…Also, evidence demonstrating the ability of MDA to control the transmission of schistosomiasis in high prevalence areas is mixed, in part because the impact of MDA will vary across different epidemiological settings. There are many regions, such as the Mekong River in Cambodia, where excellent progress has been made, with heavy-intensity infections reduced to below 1% [5, 6]. However, several recent studies in Africa have demonstrated limited progress in reducing prevalence in localized high-transmission areas, despite high MDA coverage [7–9].…”