Seasonal Fluctuations in Fly Density and Pathogen Carriage in Urban Villages of Pudong New Area

Background : Flies are significant mechanical vectors of zoonotic pathogens, posing substantial risks for diarrheal disease transmission in urban environments with substandard sanitation. Many urban villages in Shanghai's Pudong New Area exhibit conditions conducive to fly proliferation and pathogen dissemination. Methods : Our study was conducted from June to October 2024 in Taiping Village, a representative urban village in Pudong. Fly density and species composition were monitored across six environments (residential indoor/outdoor, green belts, wet market exteriors, restaurant exteriors, public toilet exteriors) using standardized cage traps and sticky ribbons following protocols. Captured flies were taxonomically identified, and 149 pooled samples were screened via RT-PCR and microfluidic chip technology for 31 enteric pathogens (viruses, bacteria, parasites). Statistical analyses employed Excel 2019 and R 4.4.3. Results : Sarcophagidae dominated the fly community (60.75%), followed by A. illocata (17.29%) and L. sericata (13.55%). Peak fly density occurred in June-August (1.48 flies/trap). Public toilet exteriors exhibited the highest density (1.33 flies/trap). Pathogen carriage was detected in 61.75% of samples, with Cryptosporidium (51.68%) and diarrheagenic E. coli (DEC, 22.82%) most prevalent. Multi-pathogen co-infection occurred in 44.12% of DEC-positive samples. Residential indoor environments showed the highest pathogen detection rate (71.43%), significantly exceeding public toilet exteriors (38.89%). Conclusion : This study identifies Sarcophagidae as the primary fly vector in Pudong’s urban villages, carrying diverse enteric pathogens—notably Cryptosporidium and DEC—with peak transmission risk during summer. The high overall pathogen carriage rate, particularly in crowded residential interiors, underscores the critical need for enhanced sanitation infrastructure, targeted vector control and community hygiene education to mitigate outbreak risks of enteric infections in these high-density settlements.