关键词: 洪涝灾区, 蚊, 蝇, 鼠, 密度, 应急监测

Abstract: Objective To investigate vector density changes in the flood-stricken areas of Hebei Province, China, so as to provide a basis for vector control and the prevention and control of vector-borne diseases in a scientific and orderly manner. Methods The daily monitoring data on the density of mosquitoes, flies, and rodents were collected at 192 resettlement sites in 21 counties/cities/districts of 7 flood-stricken prefecture-level cities in Hebei Province from August to October 2023. The density of mosquitoes and flies was monitored through visual inspection, and the density of rodents was measured using the footprint tracking method. R 4.2.2 software was used to perform the Wilcoxon signed-rank test, Friedman test, and Pearson correlation analysis. Results The average densities of mosquitoes, flies, and rodents of all the resettlement sites were 1.05 inds/labor hour, 0.45 inds/m², and 0.037 tracks/2 000 m, respectively. The average mosquito density of the resettlement sites showed a slowly fluctuating downward trend, with the highest level on the 1st day of surveillance, reaching 1.97 inds/labor hour, which was lower than the reference level for mosquito control (10 inds/labor hour). The density of flies showed a slowly fluctuating downward trend, with the higher levels on the 1st day (0.71 inds/m²) and the 25th day (1.00 inds/m²) of surveillance, approximating or reaching the reference level for fly control (1 ind/m²). The average rodent density showed a rapidly downward trend, with the peak on the 1 st day at 0.181 tracks/2 000 m, far lower than the rodent control reference level (5 tracks/2 000 m). Pest and rodent control work was completed for a total of 12 586 points covering 1 353 104 m² of three types of habitats, including resettlement sites and their surroundings, toilets, and garbage points. In August 2023, there were 729 cases of vector-borne diseases in the flood-stricken areas, which were more than the cases in the same period of 2022 (t=-1.429, P=0.002) and 2021 (t=-0.929, P=0.119), similar to the number in the same period of 2020 (t=-0.024, P=1.000), and more than the number in September 2023, the late stage of the flood disaster (W=44.500, P=0.013). From August to September 2023, the local reported no case of mosquito-borne infectious diseases, 1 case of rodent-borne typhus, and 1 215 cases of fly-related diseases (can be mechanically carried and transmitted by flies) diseases such as the other infectious diarrhea and bacillary dysentery; and the number of daily cases was not correlated with the density of flies (r=-0.195, P=0.146). Conclusions The density of mosquitoes, flies, and rodents was low at the resettlement sites of flood-stricken areas in Hebei Province in 2023. When the density exceeded the vector and rodent control reference levels, the implementation of emergency vector and rodent control effectively limited the density of vectors and rodents in the flood-stricken areas and prevented the outbreak of the related diseases.

Key words: Flood-stricken area, Mosquito, Fly, Rodent, Density, Emergency surveillance