Spatial Cluster Change of Schistosoma japonicum Transmission Foci in Indonesia During the Schistosomiasis Elimination Program

PURPOSE

The Government of Indonesia committed to eliminating schistosomiasis by 2025. Collaboratively snail control became one of the crucial strategies to ensure that the prevalence of Schistosoma japonicum in Oncomelania hupensis lindoensis reaches zero by the end of the program. This research investigated the spatial cluster change of S. japonicum transmission foci in Indonesia between 2017 and 2021.

METHODS

We mapped the snail foci, collected the snails, and calculated the snail density. We also conducted laboratory tests to detect the existence of cercariae in the snails. Identified infected snails were used to calculate the infection rate (IR) or snails' prevalence of schistosome cercariae among freshwater snails. We then analysed the spatial cluster using the Getis-Ord Gi* statistic to identify the hot and cold spots.

RESULTS

The 5-year schistosomiasis elimination program successfully declined 18.84% of the snail foci and reduced 40.37% of the infected snail foci. Local spatial autocorrelation of snail density and infection rate identified that in 2017 and 2021, the number of cold spots decreased by 53.91% and 0%, while hot spots increased by 2.63% and 56.1%. The presence of more hot spots suggests a rise in the number of foci with high snail density and infection rates. The implementation of snail control was not optimal, and the parasite transmission through domestic animals still existed, causing the spatial cluster of hot spots to change during this period. Most hotspots have been observed near settlements, primarily in cocoa plantations, developed and deserted rice fields, grassland, and bush wetlands.

CONCLUSION

During the schistosomiasis elimination program, the number of hot spots increased while cold spots decreased, and there were notable changes in the geographical distribution of hot spots, indicating a shift in the clustering pattern of schistosomiasis cases. The findings become essential for policymakers, particularly in selecting priority areas for intervention. In the Discussion section, we demonstrated the selection process based on the existence of hot and cold spots. Furthermore, we proposed that enhancing cross-sector integration is crucial, particularly in connection with the management of S. japonicum transmission through domestic animals.

Optimized strategy for schistosomiasis elimination: results from marginal benefit modeling

BACKGROUND

Poverty contributes to the transmission of schistosomiasis via multiple pathways, with the insufficiency of appropriate interventions being a crucial factor. The aim of this article is to provide more economical and feasible intervention measures for endemic areas with varying levels of poverty.

METHODS

We collected and analyzed the prevalence patterns along with the cost of control measures in 11 counties over the last 20 years in China. Seven machine learning models, including XGBoost, support vector machine, generalized linear model, regression tree, random forest, gradient boosting machine and neural network, were used for developing model and calculate marginal benefits.

RESULTS

The XGBoost model had the highest prediction accuracy with an R2 of 0.7308. Results showed that risk surveillance, snail control with molluscicides and treatment were the most effective interventions in controlling schistosomiasis prevalence. The best combination of interventions was interlacing seven interventions, including risk surveillance, treatment, toilet construction, health education, snail control with molluscicides, cattle slaughter and animal chemotherapy. The marginal benefit of risk surveillance is the most effective intervention among nine interventions, which was influenced by the prevalence of schistosomiasis and cost.

CONCLUSIONS

In the elimination phase of the national schistosomiasis program, emphasizing risk surveillance holds significant importance in terms of cost-saving.

SWOT analysis on snail control measures applied in the national schistosomiasis control programme in the People's Republic of China

BACKGROUND

Snail control is an important component in the national schistosomiasis control programme in China, by application of chemical molluscicides, forestry projects, agriculture projects and water conservancy projects in recent decades. However, there are still wide areas of snail inhabited in China which remains a great challenge to achieve the goal of schistosomiasis elimination by 2025. Therefore, a SWOT (strengths, weaknesses, opportunities and threats) analysis on snail control measures is required for precision schistosomiasis control.

METHODS

The SWOT approach, which is a well-known structured analysis tool, was used to identify and evaluate the specific characteristics of four types of snail control measures in China, including chemical mollusciciding, forestry, agriculture, and water conservancy projects. The analysis were carried out based on the information collection from literature review, of research papers, books, annual report database of national schistosomiasis control programme in China, reports from the academic forums, and so on.

RESULTS

For chemical mollusciciding, application strategy needs to focus on specific local settings, such as stage of schistosomiasis control, environmental factors, and limitations from external policies and internal deficiencies. Regarding forestry projects, the optimal strategies are to cooperate with other national forestry programmes to share the investment costs and pay attention on wetland protection. In agriculture projects, it is necessary to develop related cash crop industries and combine with national farmland consolidation projects simultaneously to increase the total economic benefits. Concerning water conservancy projects, the main purpose is to control snail migration from snail area to snail-free areas nationwide.

CONCLUSIONS

Integrated strategies for various measures application and a top-level designed cooperation mechanism will be the necessary to eliminate snail and schistosomiasis in China.

[Study on interventions based on systematic ecological system construction to interrupt transmission of schistosomiasis in hilly endemic regions]

OBJECTIVE

To study the effectiveness of comprehensive control measures based on systematic ecological system construction to interrupt the transmission of schistosomiasis in hilly endemic regions in Sichuan Province, so as to provide the evidence for adjustment of schistosomiasis prevention and control strategies.

METHODS

A high endemic area of schistosomiasis, Panao Township of Dongpo District in Meishan City, was selected as a demonstration area. The comprehensive measures for schistosomiasis control with focus on systematic ecological management were implemented, and the income of residents, indexes of schistosomiasis control effect and so on were investigated before and after the intervention and the results were compared.

RESULTS

The project based on systematic ecological system construction started in 2009 and 317.351 million Yuan was put into the construction. The construction included economic forest plant base (1 866.68 hm², 72.66% of the total farmland areas), ecological protection gardens (585.35 hm²) and so on. Totally 97.04% of historical areas with Oncomelania hupensis snails were comprehensively improved. In 2015, the peasants´ pure income per capita increased 4 938 Yuan, with the average annual growth rate of 14.69%. All the farm cattle were replaced by the machine. The benefit rate of water improvement was increased by 52.84% and the coverage rate of harmless toilets increased by 18.30%. The positive rate of serological tests for schistosomiasis decreased from 7.69% to 3.50%, and the positive rate of parasitological tests decreased from 1.18% to 0. The area with snails was decreased from 23.33 hm² to 0. The awareness rate of schistosomiasis control knowledge and correct behavior rate of the residents increased from 85.50% and 82.60% to 95.70% and 93.90% respectively.

CONCLUSIONS

The comprehensive schistosomiasis control measures based on systematic ecological management are conform to the currently actual schistosomiasis prevention and control work in hilly endemic regions, and have good ecological economic benefit and schistosomiasis control effectiveness, which provide an effectively new model of prevention and control for advancing process, consolidating the effect, finally realizing goal of interruption and elimination of schistosomiasis in hilly endemic regions.

Contribution of Mobile Teams to Efforts to Eliminate Schistosomiasis at Schistosoma haematobium in Morocco- Narrative Review Article

Since it was first diagnosed in 1914 in Marrakesh, schistosomiasis has been a public health problem in Morocco for decades. A national control program launched in 1982 has led to a considerable reduction in the incidence and morbidity associated with the disease. Consequently, the program has shifted from disease control to an elimination process launched in 1994. This process aimed to eliminate disease transmission by the end of 2004 and has helped to clear all known foci. Mobile teams were a key element that contributed to the success of this program. They played three important roles: monitoring and control, response, and the transmission of messages.