Epidemiology of schistosomiasis in China (2004-2016)

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 m² in 2020, indicating an increase relative to the respective 2019 values (0.019/0.11 m²). 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.

Polarization of intestinal tumour-associated macrophages regulates the development of schistosomal colorectal cancer

Tumour-associated macrophages (TAMs) can be divided into M1 and M2 TAMs. M2 TAMs play an important role in tumor progression, promoting a pro-angiogenic and immunosuppressive signal in the tumor. Previous studies have shown a correlation between schistosomiasis and colorectal cancer (CRC), but the specific mechanism has not been clarified. The differences between schistosomal CRC and non-schistosomal CRC were explored by analysing the clinicopathological data and survival time prognosis of schistosomal CRC and non-schistosomal CRC patients. The underlying mechanisms leading to the differences were investigated via tissue pathology experiments. Here, we investigated whether TAMs play a role in schistosomal CRC, leading to different clinicopathological features and prognoses in schistosomal CRC and non-schistosomal CRC patients and whether TAMs have a regulatory effect on the development and prognosis of schistosomal CRC. We found that schistosomal CRC and non-schistosomal CRC patients differ in age, sex, TNM staging and prognosis survival. Applying a logistic regression analysis model, the results showed that age, sex, pathological T stage and combined schistosomiasis were independent risk factors for CRC. Prognostic analysis of follow-up patients with schistosomal CRC found that the T stage, M stage and M2 TAMs numbers were independent prognostic factors for overall survival (OS). TAMs are significantly higher in tissues of schistosomal CRC than in non-schistosomal CRC patients, especially M2 TAMs. Studies on schistosomal colorectal tissue found that the expression of M2 TAMs increased with the malignant process of intestinal tissue. In summary, schistosomal CRC and non-schistosomal CRC patients have different clinicopathological features and prognosis, schistosomiasis is a risk factor for CRC and M2 TAMs are independent prognostic factors for OS.