Objective To investigate the seasonal variation of mosquito density and species diversity of mosquitoes in Tangshan, China, and to provide a scientific basis for effective mosquito prevention and control. Methods The mosquito surveillance data were obtained, using the light-trap method, from five surveillance sites in urban residential areas, parks, hospitals, suburban residential areas, and livestock sheds, in Tangshan, from May to October of each year during 2007-2018. The data were then used for measurement, comparison, and analysis of the density, species diversity, and seasonal variation of mosquitoes in different years/months and habitats. In this study, the Shannon-Wiener diversity index, Pielou uniformity index, Berger-Parker dominance index, and relative species abundance were used to study the diversity of mosquitoes. Results A total of 10 mosquito species were captured, i.e., Culex pipiens pallens, Cx. tritaeniorhynchus, Cx. modestus, Cx. vagans, Cx. fuscanus, Aedes albopictus, Ae. vexans, Ae. dorsalis, Anopheles sinensis, and An. yatsushiroensis. The mosquito density was 1.70 mosquitoes/light·hour, with the highest density observed for Cx. pipiens pallens (1.65 mosquitoes/light·hour). The composition of different mosquito species was different in different years ( χ ²=3 393.930, P<0.001). Among the different habitats, livestock sheds had the highest density of 2.94 mosquitoes/light·hour. According to the analysis of species diversity indices in different habitats, the diversity index and uniformity index of residential areas were the highest (0.23 and 0.14, respectively), and the dominance index of rural residential areas was the highest (0.98). The seasonal variation curve of mosquito density was unimodal, with a peak (3.75 mosquitoes/light·hour) observed in July. The species diversity index and uniformity index were the highest in August (0.31 and 0.17, respectively), and the dominance index was the highest in October (0.99). Conclusion Culex pipiens pallens is the dominant mosquito species in Tangshan. The highest mosquito density was observed in livestock sheds, and the mosquito species were most abundant in residential areas, with the most uniform density of different mosquito species. The highest dominance index was observed in rural houses. The highest mosquito density was observed in July, and the mosquito species was most abundant in August, with the most uniform density of different mosquito species, the highest dominance index was observed in October.

Objective To analyze the population density distributions of adult mosquitoes in different years in Tangshan, Hebei province, China, and to predict future mosquito density by using the autoregressive integrated moving average (ARIMA) model. Methods The lamp trapping method was used to monitor the densities of various adult mosquito populations in different habitats of urban Tangshan from 2010 to 2018. The ARIMA model was established based on the data of the total densities of mosquitoes in each month from 2010 to 2017. Then this model was used to predict the total densities of mosquitoes in every month of 2018, and the prediction effect was evaluated according to the actual densities monitored in 2018. Results During 2010 to 2017, the total density of mosquitoes in urban Tangshan was 2.14 individuals per lamp hour, and Culex pipiens pallens was the dominant species, accounting for 98.02% of the total number of captured mosquitoes. Among different habitats, livestock sheds had the highest mosquito density of 3.65 individuals per lamp hour. There was a significant difference in the composition ratio of mosquito species between different habitats ( χ ²=249.177, P<0.001). During the eight years, the highest mosquito density (3.00 individuals per lamp hour) was observed in 2014, and the lowest density (1.41 individuals per lamp hour) in 2016. Seasonal fluctuations in the total density of mosquitoes showed a single-peak curve, with the peak at 4.71 individuals per lamp hour in July. An ARIMA model was used to fit the total densities of mosquitoes in urban Tangshan in every month from 2010 to 2017. ARIMA (0, 1, 1)×(2, 1, 0) ₁₂ was selected as the best model, and the residual sequence was a white noise sequence ( Q=20.654, P=0.148). Then the model was used to predict the total densities of mosquitoes in 2018, and the actual values fell within the 95% confidence interval of the predicted values. The predicted seasonal fluctuations in mosquito density were quite close to the actual values, suggesting this model could be used to predict mosquito density in short and medium term. Conclusion By analyzing the densities of mosquito populations and seasonal fluctuations in Tangshan, the ARIMA model was successfully established to predict future mosquito density, so as to effectively warn the outbreak and epidemic of mosquito-borne diseases.

Objective To investigate the change in population density of mosquitoes and the resistance to commonly used insecticides against larvae and adults of Culex pipiens pallens in Tangshan city, and to provide a scientific basis for mosquito control for 2016 International Horticultural Exposition. Methods The mosquito lamp method was used to determine the population density of mosquito adults for International Horticultural Exposition park and surrounding area during 2013 to 2016. The larval immersion method and the adult exposure tube method were used to determine the resistance of Cx. pipiens pallens to commonly used insecticides. The DPS software was used to calculate the median lethal concentration and its 95%CI, virulence regression equation and Chi-square values. The resistance level of different insecticides was compared with Wilcoxon H test by SPSS 17.0 software. Results The average density of mosquitoes was 4.641 per lamp hour in Tangshan city from 2013 to 2016, with the predominant species Cx. pipiens pallens. The highest average density was found in the barn among all habitats (10.556 per lamp hour). Culex pipiens pallens were the predominant species in all surveillance areas. The population density of mosquitoes showed a single-peak throughout the year, peaking in July, being 10.854 per lamp hour. Larval Cx. pipiens pallens were susceptible to DDT, cypermethrin, temephos, chlorpyrifos, tetramethrin, bendiocarb and pyriproxyfen, with the resistance ratio of 0.88, 1.94, 0.82, 0.50, 2.18, 0.53, and 0.02, respectively. All of tested larval mosquitoes were intermediately resistant to bifenthrin with the resistance ratio of 14.00 and highly resistant to ethofenprox with the resistance ratio of 57.00. Culex pipiens pallens adults showed a mortality of 25.00% when contacted deltamethrin for 1 h and mortality of 50.00% when contacted permethrin for 3 h, all tested adults were resistant to deltamethrin and permethrin. Culex pipiens pallens adults experienced 100% mortality when contacted propoxur for 2 h, which was considered susceptible. Conclusion The predominent species were Cx. pipiens pallens, density peaked in July, when comprehensive control measures should be taken. More considerations are warranted about how to choose carbamate, organophosphorus and organochlorine insecticides, prevent or slow down the occurrence of the resistance.

Objective To understand the resistance of main vectors to commonly-used insecticides by the successive investigation in Tangshan International Horticultural Exposition park and surrounding areas from 2012 to 2016, and to provide the scientific basis for vector control. Methods Using dipping, topical application and residual film methods to measure the resistance of Culex pipiens pallens, Musca domestica, and Blattella germanica. Results The resistance ratio of Cx. pipiens pallens to temephos, chlorpyrifos, cypermethrin, tetramethrin and DDT were 0.82, 0.50, 1.94, 2.18, and 0.88, and all considered susceptible. As compared with the previously recorded results(1983, 1991), however, Cx. pipiens pallens showed increased tolerance to deltamethrin in 2009-2011. The resistance ratio of M. domestica to tetramethrin, beta-cyfluthrin, alpha-cypermethrin, deltamethrin, and azamethiphos were 3.13, 2.21, 7.07, 100.67, and 6.71, respectively. Musca domestica had low resistance to tetramethrin, beta-cyfluthrin, alpha-cypermethrin, and azamethiphos, and with high resistance to deltamethrin. As compared with the previously reported results(1983), M. domestica showed increased resistance to deltamethrin in 2012-2016,and slightly decreased compared with 1991. The resistance ratio of B. germanica to cypermethrin, deltamethrin, tetramethrin, beta-cyfluthrin, and chlorpyrifos were 37.28, 18.61, 35.95, 27.05, and 17.04, and all considered high resistance. Conclusion Choosing high sensitive pesticides to reasonably kill vectors will ensure effective prevention and control of the vectors for 2016 International Horticultural Exposition.

Objective To assess and prevent the risks caused by vectors and the vector-borne disease during 2016 International Horticultural Exposition. Methods Judging the hazard caused by vectors and the risk classification of vector-borne diseases by risk assessment index matrix method and Borda sequence value method. Results It was high risk for the vector biting and infestation and food poisoning caused by vectors, it was middle risk for the cable damage and communication and power facility disruption. The prevalence of Japanese encephalitis (JE), malaria, plague, and hemorrhagic fever with renal syndrome (HFRS) were at high risk. The prevalence of dengue fever, yellow fever, filariasis, Zika virus disease, leptospirosis, murine typhus, and tsutsugamushi disease were at middle risk. Food poisoning caused by vectors ranked the first in vector harm by Borda sequence value method, vector biting and infestation and communication and power facility disruption by vectors ranked the second. JE, malaria, and HFRS ranked the first in vector-borne diseases. Dengue fever, yellow fever, filariasis, Zika virus disease, leptospirosis, murine typhus, and tsutsugamushi disease ranked the forth. Plague ranked the eleventh. Conclusion The integrated application of risk matrix and Borda count is effective in assessing the risk levels of the hazards caused by vectors and the vector-borne disease, and therefore is worthy of wide promotion.

Objective To investigate the community structure and seasonality of main vectors in Tangshan city in 2015, and to provide the scientific basis for vectors control and prevention of vector-borne diseases during the 2016 International Horticultural Exposition. Methods Light trap, cage trap,mouse trap and glue trap were used to catch mosquitoes, flies, rodents and cockroaches respectively in different urban and rural areas in Tangshan from January to December in 2015. Results The mosquitoes were mainly Culex pipiens pallens and Anopheles sinensis, the average density of mosquitoes was 2.65 per lamp hour, with the predominant species being Cx. pipiens pallens, which accounted for 99.42%. The flies were mainly Musca domestica, Lucilia sericata, Boettcherisca peregrina and Muscina stabulans. The average fly population density was 3.63 per cage, with the predominant species being B. peregrina, which accounted for 46.18%. The rodents were mainly Rattus norvegicus and Mus musculus, the average density of rodents was 0.32%, with the predominant species being R. norvegicus, which accounted for 52.17%. The cockroaches with the predominant species was Blattella germanica, the average density of cockroaches was 0.08 per sticky trap, and the infestation rates was 5.33%. Most mosquitoes and flies prevailed in May; the former became most active in July and the latter in June and September. Rats and cockroaches were observed throughout the year with relatively high density in May for rats and in July for cockroaches. Conclusion The community structure and seasonality of main vectors were preliminarily understood through monitoring to ensure the success of the 2016 World Horticultural Exposition and provide the basic information for vector-borne disease control and prevention.