Impact of the coronavirus disease 2019 lockdown on Schistosoma host Oncomelania hupensis density in Wuhan

BACKGROUND: Snails that host the parasitic worm Schistosoma were once controlled or eliminated in Wuhan, China. However, safety measures associated with the outbreak of novel coronavirus disease 2019 (COVID-19) halted snail detection and extermination efforts. The impact of the COVID-19 pandemic on urban schistosomiasis transmission remains unclear. This study aimed to investigate snail density and the associated risk of a schistosomiasis outbreak in Wuhan. METHODS: The density and infection status of snails were monitored by global positioning system satellites, and outbreak risk was calculated by adjusting the Kaiser model. SigmaPlot was used to create a three-dimensional risk matrix. RESULTS: The living snail frame occurrence rate was 1.48%, and the average living snail density was 0.054/0.11 m(2) in 2020, indicating an increase relative to the respective 2019 values (0.019/0.11 m(2)). No infectious snails were observed in the survey area. The possibility, harmfulness, and uncontrollability indicator values were 0.842, 0.870, and 0.866, respectively. The areas at greatest risk were the northern bank of Tianxingzhou and the Tianxingzhou and Hongshan districts overall. The existing snail sites in the northern bank of Tianxingzhou exhibited the highest risk scores, followed by those in Pak Sha Chau, with the highest risk score found in Yangsiji Village. The events likely to occur in Hongshan District were also likely to have high severity. CONCLUSIONS: During the COVID-19 outbreak, the risk of schistosomiasis increased due to snail colonies returning to their sites of origin in Wuhan, suggesting a need for strengthened infection control and prevention measures.