Impact of Coronavirus Disease 2019 on Snail`s Density of Schistosoma`s Host in Wuhan
Authors: LI Guangming , XU Dandan , HU Yanfang , XU Mingxing , ZHANG Longjiang , DU Xiaoan , ZHANG Ling , SUN Chao , XIE Yaofei , Tan Xiaodong 
Published: April 2021

Abstract
Background:

The density of snails among schistosomiasis hosts has been kept at a low level and even disappeared in many places in Wuhan. However, from the beginning of the epidemic to the lifting of the seal in Wuhan, which the work of snail detection and extermination has been at a standstill. In order to analyze the potential harm of Coronavirus disease 2019 (COVID-19) on urban schistosomiasis transmission, we investigated the density of snails in the Jiangan and Hongshan districts of Wuhan, which evaluated the possibility of schistosomiasis outbreak in Wuhan city.
Methods

The density and infection status of snails were monitored by GPS satellite, which the risk value was calculated by adjusting Kaiser model. SigmaPlot was used to draw a three-dimensional risk matrix.
Results

(i)The living snail frame occurrence rate was 1.48% and the average living snail density was 0.054/0.11 m2 in 2020. Compared with that in 2019, the area of existing snails Tianxingzhou increased greatly. The area of historical snails was 24187 m2 has increased which the average density of living snails was 0.019/0.11 m2. No infectious snails were found in the survey area. (ii) Experts have high enthusiasm (E = 100%). The authority of experts on the indicators of possibility, harmfulness and uncontrollability is 0.842, 0.870 and 0.866 respectively, all greater than 0.7, indicating that expert evaluation is authoritative. After adjusting the Kaiser model, the top three risk values were the north bank of Tianxingzhou, Tianxingzhou as a whole, and Hongshan as a whole. The existing snail sites in the north bank of Tianxingzhou had the highest risk value and ranked the second Pak sha Chau. The highest risk value was found in the historical snail village of Yangsiji village. The risk events on the north bank of Tianxingzhou are located in the orange zone, which belongs to the high-risk area. The whole Hongshan District, the existing snail Tianxingzhou and the tail of Tianxingzhou are located in the yellow zone, belonging to the moderate risk area. Other risk events are located in the blue or green zones and are in the low risk or negligible sub-zone. (iii)The three dimensional risk matrix shows that the potential risk level of the existing snail spot and the possibility of risk occurrence of Tianxingzhou is high. The existing snail points on the Pak sha Chau, indicating the severity of the risk event; Historical snails, indicating the unpredictability of risk events once they occur. The emergency monitoring points show that once the risk event occurs, the level of uncontrollability rises instantly. The whole Hongshan district indicates the severity of the occurrence of the risk event.
Conclusion

Under the influence of Covid-19 epidemic, the risk of schistosomiasis infection was high and the historical snail snail appeared again in Wuhan. Therefore, the prevention and control work of schistosomiasis infection should be strengthened in Wuhan.