Objective To investigate the resistance levels of Blattella germanica in Wuhu, Anhui Province, China, so as to provide a scientific basis for rational insecticide use. Methods From March to June 2022, test B. germanica cockroaches were collected from restaurants, bakeries, hotels, supermarkets, and farmers' markets in Yijiang, Jinghu, Sanshan, and Jiujiang districts of Wuhu. The resistance of B. germanica to 12 commonly used insecticides was determined using the residual film method. SPSS 22.0 was used for data processing and analysis. Results The 24 h mortality rates of B. germanica treated with permethrin, tetramethrin, cypermethrin, deltamethrin, alpha-cypermethrin, beta-cypermethrin, lambda-cyhalothrin, propoxur, azamethiphos, acephate, dichlorvos, and chlorpyrifos were 91.20%, 18.40%, 91.33%, 89.47%, 77.85%, 92.62%, 99.19%, 100%, 96.85%, 100%, 76.06%, and 99.00%, respectively. The median knockdown time (KT ₅₀) was 32.63, 900.61, 28.17, 30.47, 26.60, 11.06, 16.54, 17.93, 14.13, 59.66, 27.57, and 38.21 min, respectively. According to the resistance criteria by mortality, B. germanica in Wuhu was sensitive to lambda-cyhalothrin, propoxur, azamethiphos, acephate, and chlorpyrifos; potentially resistant to permethrin, cypermethrin, deltamethrin, and beta-cypermethrin; and resistant to tetramethrin, alpha-cypermethrin, and dichlorvos. Based on the knockdown resistance criteria, B. germanica in Wuhu was sensitive to azamethiphos; lowly resistant to beta-cypermethrin, lambda-cyhalothrin, propoxur, acephate, and chlorpyrifos, with the resistance ratios being 2.58, 3.21, 1.39, 2.01, and 1.41, respectively; moderately resistant to permethrin, cypermethrin, deltamethrin, alpha-cypermethrin, and dichlorvos, with the resistance ratios being 6.54, 6.39, 7.79, 5.58, and 7.14, respectively; and extremely high resistant to tetramethrin, with the resistance ratio being 259.54. KT ₅₀ or 24 h mortality had no significant correlation with insecticide consumption ( r _{KT50-inseciticide consumption}=0.045, r _{24 h mortality-insecticide consumption}=0.141, all P>0.05). Conclusions B. germanica in Wuhu has developed medium or high resistance to a variety of insecticides. In cockroach control, the use of insecticides should be regulated according to the results of resistance monitoring to delay the development of resistance.

Objective To investigate the species composition and distribution of ectoparasitic chigger mites on the rodents in some areas of Heihe, Heilongjiang province, China. Methods Rodents were captured using rat snap traps in Aihui district, Xunke county, and Wudalianchi of Heihe in mid-September, 2015. Chigger mites were collected from the body surface of rodents. The species of chigger mites was identified according to their morphologic characteristics, and the species of rodents and pikas were identified by morphology and DNA barcoding technique. The species composition, chigger infestation rate, chigger index in each area and habitat were calculated and analyzed. The nucleic acid of Orientia tsutsugamushi was detected by nested PCR. Results A total of 170 rodents were captured, involving 8 species of 6 genera from 3 families under 2 orders. Myodes rutilus (38.26%), Ochotona mantchurica (34.78%), and M. rufocanus (14.78%) were the dominant species in the volcanic geopark of Xunke county. Apodemus agrarius was the dominant species in the farmland of Wudalianchi (76.67%) and Aihui district (64.00%). Or. tsutsugamushi was negative in all rodents captured. No chigger mite was found on the bodies of rodents from Wudalianchi and Aihui district, while 11 256 chigger mites were found on rodents from Xunke county, belonging to 5 species of 2 genera, with the dominant mite species Neotrombicula gardellai (87.50%). The main hosts of chigger mites were O. mantchurica, M. rutilus, and M. rufocanus. Conclusion The different areas of Heihe have distinct species compositions of rodents, and different species of rodents carry distinct numbers of chigger mite.

Objective To investigate the epidemic situation of dengue fever in Cambodia, the main source of imported cases to China, and the main influencing factors for imported dengue fever from Cambodia to China, and to help formulate targeted response measures and effectively prevent imported cases from abroad. Methods Dengue fever information in Cambodia from 2011 to 2019 was collected from the official website of the World Health Organization and the official account of Public Health Concerns at Frontier Ports. The information about dengue fever cases imported to China from Cambodia was extracted from the China Information System for Disease Control and Prevention. The number of tourists from China to Cambodia was inquired on the website www.chinaqw.com. Excel 2016 software was used to analyze the trend of dengue fever epidemic in Cambodia, the annual growth rate of the number of tourists from China to Cambodia, and the data on cases of dengue fever imported from Cambodia to China from 2011 to 2019. SPSS 19.0 software was used to perform partial correlation analysis. Results During 2011 to 2019, Cambodia had the highest incidence of dengue fever in 2019. In 2018, the proportion of cases of dengue fever from Cambodia increased sharply among total imported cases in China. In 2019, Cambodia became the main source of China's imported cases. At the same time, the number of Chinese residents visiting Cambodia increased year by year. The partial correlation coefficient between the proportion of dengue fever cases from Cambodia and Cambodia's incidence of dengue fever was 0.880 ( P=0.004); the partial correlation coefficient between the proportion of dengue fever cases from Cambodia and the number of tourists to Cambodia was 0.887 ( P=0.003). Conclusion The number of cases of dengue fever in Cambodia and the number of tourists from China to Cambodia are important factors affecting the number of imported cases in China. Chinese authorities should pay close attention to the incidence of dengue fever and the number of floating population in neighboring countries with close interactions.

Objective To analyze the number and composition of Meriones unguiculatus nest fleas in Kangbao pasture, a natural plague focus in Hebei province, China, 2016-2019, to study the changes in the number of M. unguiculatus nest fleas, and to explore a statistical method for analyzing the seasonal distribution of plague vector fleas. Methods Based on the average flea index of M. unguiculatus nest fleas in different months of 2016-2019, the seasonal distribution of the nest fleas was analyzed by the concentration degree method and circular distribution method. The Watson-Williams test was used for hypothesis testing. Results A total of 138 M. unguiculatus nests were detected, in which 35 nests (25.36%) were infested by fleas. In total, 317 fleas were collected, involving 5 species of 4 genera of 3 families. The average flea index was 2.30. Through the year, the number of fleas collected was largest in July, second largest in October, and then in September. Neopsylla bidentatiformis, Nosopsyllus laeviceps kuzenkovi, and N. abagaitui showed double peaks, while Frontopsylla luculenta and Citellophilus tesquorurn mongolicus showed a single peak. According to the concentration degree analysis, the M value was 0.5-0.7 in 2016 and 2017, >0.9 in 2018, and 0.7-0.9 in 2019. The circular distribution analysis found that there was no angular mean in 2016; there were angular means in 2017-2019, but the means were not equal ( F=3 714.353, P<0.05). For 2017 and 2019, the mean angle existed, and a=115.76° ( r=0.535, Z=21.007, P<0.001); the increase of the number of M. unguiculatus nest fleas peaked on April 27-28, with the peak period during February 20 to July 1. For 2018, the mean angle existed, and a=167.24° ( r=0.995, Z=6.806, P<0.001); the peak point of the increase was on June 18-19, and the peak period was from June 8 to June 30. Conclusion The concentration degree method and circular distribution method show that the change in the number of M. unguiculatus nest fleas is seasonal, with the peak point at the beginning of summer and the peak period during spring and summer, which is consistent with the seasonal fluctuation curve. Both methods can be used to study the seasonal fluctuation of fleas. The concentration degree is suitable for data exploration, and the circular distribution method is suitable for determination of peak point and peak period.

Objective To analyze the epidemiological characteristics of Japanese encephalitis (JE) in eight provinces and municipalities of northern China (Gansu, Ningxia Hui Autonomous Region, Shaanxi, Shanxi, Hebei, Beijing, Tianjin, and Liaoning) from 2005 to 2019, to investigate the pattern of the development of JE, and to provide a scientific basis for effective prevention and control of JE. Methods A descriptive epidemiological analysis was performed for JE cases in the above eight northern provinces and municipalities from 2005 to 2019, which were collected through the China Information System for Disease Control and Prevention and JE Surveillance Information Reporting and Management System. Results From 2005 to 2019, the mean annual incidence rate of JE was 0.14/100 000 and there were 390 deaths, with a case fatality rate of 7.25%. The distribution of JE expanded from 157 counties/districts in 2005 to 254 counties/districts in 2018. The number of cases from August to September accounted for 81.26% of all cases, and August and September were the peak periods for the onset of JE. The proportion of patients aged 0-14 years decreased from 54.55% in 2005 to 3.96% in 2019, and the proportion of patients aged ≥ 15 years increased from 45.18% in 2005 to 96.03% in 2019 ( χ ² _trend=998.524, P<0.001). Farmers, preschool and scattered children, and students accounted for 58.76%, 14.81%, and 12.38%, respectively. The proportion of farmers increased from 37.19% in 2005 to 79.21% in 2019. Conclusion The distribution of JE has expanded in the eight provinces and municipalities of northern China, and age distribution tilts toward high age. As for occupational composition, there is an increase in the proportion of farmers.

Objective To implement sustainable vector control strategies and measures for Japanese encephalitis (JE) by carrying out integrated mosquito prevention and control (IMPC) in developing rural areas of Gansu province as a health, poverty alleviation, and public welfare activity in 2019, and to provide a IMPC package for mosquito control in high-prevalence areas of JE in China. Methods The activity was jointly proposed by professional institutes and social organizations, technically guided by disease control specialists, and implemented by several enterprises and voluntary teams engaged in pest control operation (PCO). Zhaoshi village in Bali town, Jingning county, Pingliang, Gansu province, with the highest incidence rate of JE in 2017, was selected, and integrated management strategies were carried out, including public education for villagers, thorough elimination of mosquito larvae breeding sites, and chemical control in key areas. During the activity, the lamp trapping method was used to monitor the change in mosquito density to evaluate the effect of integrated mosquito control. Results A total of 41 enterprises participated in the activity, and 19 technical specialists and 37 PCO volunteers formed the team of volunteers. Investigation before control showed that bonsai, aquatic plants, cisterns, tanks, and basins were the main containers for water accumulation, with a positive rate of water accumulation of 34.32% and a 100-household index of 85.33. Main mosquito breeding sites in the external environment within and around the village included pipe wells, sewer water, open channels, sewage lagoons, unused bowls/bottles/tanks/cans, and waste tires, with a positive rate of 17.31%. The results of monitoring before control showed that the density of adult mosquitoes was 50.33 mosquitoes/trap/night, and Culex tritaeniorhynchus was the dominant species accounting for 80.13%, followed by Cx. pipiens pallens accounting for 12.91% and Anopheles sinensis accounting for 5.96%. After the first time of prevention and control, the density of adult mosquitoes was reduced to 11.60 mosquitoes/trap/night, with Cx. pipiens pallens accounting for 43.11%, Cx. tritaeniorhynchus accounting for 17.24%, An. sinensis accounting for 5.17%, and other mosquito species accounting for 34.48%, and the mean reduction rate of mosquito density was 76.95%. After the second time of prevention and control, the total mosquito density was reduced to 6.67 mosquitoes/trap/night, with An. sinensis accounting for 42.50%, Cx. pipiens pallens accounting for 17.50%, Cx. tritaeniorhynchus accounting for 15.00%, and other mosquito species accounting for 25.00%; the mean reduction rate of mosquito density was 86.75%, and the reduction rate of peasant households reached 100%. With the implementation of integrated mosquito prevention and control measures, the composition ratio of Cx. tritaeniorhynchus decreased from 80.13% to 15.00%. There was a significant reduction in mosquito larvae breeding sites after on-site public education and treatment, with a reduction rate of 93.24% based on container index. Conclusion The sustainable mosquito control mode of monitoring, control, and evaluation has a good effect in spreading the knowledge of mosquito prevention and control and reducing mosquito density and can be widely used in the high-prevalence areas of JE in China. Such measures should be taken in accordance with local conditions to achieve a better effect.

Objective To establish a RT-hemi-nested PCR assay for laboratory detection of mosquito-borne alphaviruses based on the universal primers of mosquito-borne alphaviruses. Methods Three universal primers of mosquito-borne alphaviruses were designed in the conserved regions based on the whole genome sequence of alphaviruses in GenBank. The RT-hemi-nested PCR assay was established using the cDNAs of Sindbis virus (SINV) and Chikungunya virus (CHIKV) as templates under optimized conditions; the sensitivity and specificity of this method were validated and mosquitoes collected in the field were tested. Results The sensitivity test results showed that the lowest detection limit of SINV and CHIKV was 3×10 ³ and 3×10 ⁴ copies/µl. The sensitivity test results showed that the RT-hemi-nested PCR was only able to amplify the alphavirus. The established method was used to detect mosquito specimens collected in the field. The results showed that mosquito-borne alphavirus was not detected in all samples . Conclusion The RT-hemi-nested PCR assay established in the study is highly specific and sensitive and can be used for epidemiological survey on alphavirus infection.

Objective To rear Xenopsylla cheopis, and to observe and record its morphological changes and characteristics in various stages of life cycle. Methods Xenopsylla cheopis was reared and bred using wet filter papers combined with petri dishes. Stereomicroscope and microscope imaging system were used to collect, observe, and record the morphological changes and characteristics of X. cheopis in each life-stage. Results The images of morphologic changes of X. cheopis in "egg-larval-pupal-adult" stages were obtained. The period from the eggs being laid to the offspring emerging as adults lasted 26-35 days, including 2-7 days of egg stage, 6-19 days of larval stage, 10-22 days of pupal stage, and 26-60 days of adult stage. The number of eggs laid and the number of larvae hatched followed the circulation mode of "peak-trough" with the time of blood supply. Conclusion There are time-points of morphological changes and developmental stages in the life cycle of X. cheopis, which can provide targets for its precise control.

Objective To analyze the national surveillance data of rodents in China, 2019, and to provide a basis for improving the quality of national rodent surveillance and formulating scientific control measures. Methods Eighty-nine prefecture-level cities were set up as surveillance sites in 30 provinces (autonomous regions and municipalities) and Xinjiang Production and Construction Corps. Rodents were captured once every two months in three habitats by night-trapping, night-cage and sticky board methods. The surveillance data of rodents were collected and sorted to analyze the species composition, distribution, and seasonal density fluctuation of rodents. Results A total of 4 317 rodents were captured in 2019, with a total density of 0.78 rodents/100 traps. Cage trapping had the highest density of captured rodents, followed by sticky trapping. Rattus norvegicus, Mus musculus, and R. tanezumi accounted for 47.30%, 27.89%, and 12.55% of the total rodents captured, respectively. The highest density of rodents was in rural residential areas among three habitats. The density of rodents first increased and then decreased all year round, and peaked in May. Conclusion The density, species composition, and seasonal fluctuation of rodents at national surveillance sites across China in 2019 show no significant differences from the results in 2005-2016. Local authorities should assess risks and formulate control strategies based on their surveillance results of previous years.

Objective To investigate the genotypes and distribution characteristics of the ace gene of the dengue vector Aedes albopictus (field population) in different regions of China, and to preliminarily explore their resistance mechanism to organophosphorus and carbamate insecticides. Methods A total of 422 larvae, pupae, or adults of Ae. albopictus were collected at 14 sampling sites (14 geographical populations) in Haikou of Hainan province, Guangzhou of Guangdong province, Jinghong of Yunnan province, and Xingyi of Guizhou province from June to September 2018, and they were identified by morphology or molecular biology, soaked in anhydrous ethanol, and stored at -20℃. DNA was extracted from individual mosquito, and the partial fragment of the ace gene was amplified by PCR, sequenced, and analyzed for mutation at G119. Results There were only a few base mutations but no amino acid mutations at G119 of the ace gene. Two alleles were detected, namely wild-type GGA/G (832/98.58%) and mutant-type GGG/G (12/1.42%), and one genotype was detected, namely wild-type homozygote G/G (422/100%). Conclusion Only a few individuals of Ae. albopictus showed a base mutation at G119 of the ace gene, but the base substitution did not cause the corresponding amino acid mutation. Therefore, the resistance mechanism of Ae. albopictus to organophosphorus and carbamate insecticides needs to be further explored.

Objective To investigate the levels and distribution of resistance of Aedes albopictus to several commonly used insecticides in different areas of China, and to provide guidance for the resistance control and use of insecticides in China. Methods Excel 2016 software was used to collect and organize the bioassay data on the resistance of larval and adult Ae. albopictus to pyrethroids, carbamates, and organophosphorus insecticides in China from 2017 to 2018, and the level of resistance was statistically analyzed. ArcGIS 10.3 software was used to draw the resistance map of different insecticides. Results By collecting monitoring data in 2017 and 2018 and reviewing the relevant literature, we obtained the bioassay data on the resistance of Ae. albopictus to commonly used insecticides in 15 provinces, and then analyzed the data on the resistance to pyrethroids (deltamethrin, permethrin, and beta-cypermethrin), carbamates (propoxur), and organophosphates (malathion, temephos, and DDVP). Aedes albopictus larvae developed medium and high resistance to deltamethrin, permethrin, and beta-cypermethrin at 34 (85.00%), 18 (75.00%), and 33 (78.57%) monitoring sites, respectively, and the adult mosquitoes developed resistance or high resistance to deltamethrin, permethrin, and beta-cypermethrin at 34 (61.82%), 8 (34.78%), and 11 (34.38%) monitoring sites, respectively. Aedes albopictus larvae developed medium and high resistance to propoxur and temephos at 5 (27.78%) and 14 (36.84%) monitoring sites, respectively, and the adult mosquitoes developed resistance to propoxur and temephos at 7 (20.59%) and 4 (14.29%) monitoring sites, respectively. Conclusion Both adult and larval Ae. albopictus in most areas of China, especially coastal areas such as Guangdong and Fujian provinces, has developed high levels of resistance to pyrethroid insecticides; the resistance levels of carbamates and organophosphorus insecticides are relatively low. Local use of insecticides should be guided based on local conditions and the monitoring results; high-resistance insecticides should be stopped for a period of time, and the insecticides to which Ae. albopictus has developed medium and low resistance or suspected resistance should be used alternately or in combination.

Objective To investigate knockdown resistance ( kdr) genotypes and their distribution in the field populations of the dengue vector Aedes albopictus in different areas of Jinghong, Yunnan province, China, and understand their insecticide resistance levels, and to provide a basis for scientific control of Ae. albopictus. Methods Collected adults of Ae. albopictus were identified by morphology, and then soaked in anhydrous ethanol and stored at -20℃. DNA was extracted from each mosquito, and PCR was used to amplify the partial fragment of the voltage-gated sodium channel ( VGSC) on the nerve cell membrane. Then sequencing was performed to analyze single or multiple point mutations. Results A total of 160 Ae. albopictus mosquitoes were collected from the east, south, west, north, and middle of Jinghong in September 2018 and July 2019. Mutations were detected at the V1016, I1532, and F1534 loci of the VGSC gene. There were two alleles at the V1016 locus, namely wild-type GTA/V (239/74.69%) and mutant GGA/G (81/25.31%); three genotypes, i.e., the wild-type homozygote V/V (91/56.88%), wild/mutant heterozygote V/G (58/36.25%), and mutant homozygote G/G (11/6.88%). There were two alleles at the I1532 locus, namely wild-type ACC/I (309/96.56%) and mutant ATC/T (11/3.44%); two genotypes, i.e., the wild-type homozygote I/I (149/93.13%) and wild/mutant heterozygote I/T (11/6.87%). There were four alleles at the F1534 locus, namely wild-type TTC/F (92/28.75%), mutant TCC/S (221/69.06%), mutant TGC/C (6/1.88%), and mutant TTG/L (1/0.31%); five genotypes, i.e., the wild-type homozygote F/F (10/6.25%), wild/mutant heterozygotes F/S (69/43.13%) and F/L (1/0.63%), and mutant homozygotes S/S (77/48.13%) and C/C (3/1.88%). Conclusion The kdr gene mutation rate is high in Ae. albopictus in Jinghong, and shows a trend towards a high level and diversified development. This suggests that close attention should be paid to the insecticide resistance level, so as to guide scientific and rational use of insecticides.

Objective To understand distribution patterns and influencing factors for the interval between onset and diagnosis of typhus in China, and to provide a scientific basis for accurate prevention and control of typhus. Methods Descriptive statistical methods were used to analyze the distribution patterns of the interval between onset of disease and diagnosis. The Kruskal-Wallis H test was conducted for statistical difference analysis. Multivariate logistic regression was used to analyze the influencing factors. Results A total of 29 211 typhus cases were reported in China from 2005 to 2017. Those cases were from 29 provinces (autonomous regions and centrally administered municipalities). The median interval between onset of disease and diagnosis was 7 days. The interval was between 0 and 20 days for 92.20% of the cases. The median interval between onset of disease and diagnosis was 6 days for males and 7 days for females. Students and scattered children had longer time intervals between onset of disease and diagnosis than others. Hebei, Guangdong, and Shandong provinces had shorter time intervals, while Sichuan and Liaoning provinces had longer time intervals. Conclusion There is a long interval between onset and diagnosis of typhus in China. To accurately diagnose, treat, prevent, and control typhus, action should be taken to specifically address this issue.

Objective To explore the health risk assessment for operators and residents using public health pesticides with developed resistance. Methods This paper refers to WHO's Generic risk assessment model for indoor residual spraying insecticides in 2018, attempts to conduct a preliminary health risk assessment based on 4 pesticidal active ingredients (beta-cypermethrin, alpha-cypermethrin, deltamethrin and permethrin), 3 types of formulation and 8 commercial products registered in China, and try to carry out their resistance health risk assessment. Results Most of risk levels to health are basically acceptable when adult Aedes albopictus, Ae. aegypti, and Culex pipiens pallens mosquitoes develop low levels of resistance to pyrethroids. Under high resistance ratios (50-fold for operators, 20-fold for residents) in these species, however, most risk levels to health are not acceptable. Conclusion The research and results are helpful to expand the study field of mosquito resistance and health risk assessment and analysis of influencing factors,so as to ensure the health and safety of operators and residents. It is necessary to strengthen resistance monitoring, improve pesticide usage, promote health risk assessment in integrated vector management.

Objective To investigate the mutations in the knockdown resistance ( kdr) gene of dengue vector Aedes albopictus in Haikou, China, as well as genotypes and their distribution in different areas, to analyze the influencing factors on insecticide resistance for scientific control of Ae. albopictus. Methods In June and July, 2018, the larvae and pupae of Ae. albopictus were collected from the urban and suburb areas of Haikou and reared to adults. The collected individuals were identified by morphology and were cryopreserved at -20℃ with anhydrous ethanol. DNA was extracted from a single mosquito, partial fragments of the voltage-gated sodium channel gene on nerve cell membrane were amplified by PCR, and sequencing was performed to analyze the mutations in the kdr gene. Results In the 94 Ae. albopictus mosquitoes in the east, south, west, north, and middle of Haikou, mutation was detected at the F1534 locus of the kdr gene. There were four alleles at the 1534 locus, namely, wild-type TTC/F (113/60.11%), mutant TCC/S (66/35.11%), mutant TCG/S (1/0.53%), and mutant TGC/C (8/4.26%); there were six genotypes, i.e., homozygous wild-type F/F (39/41.49%), wild/mutant heterozygote F/S (33/35.11%) and F/C (2/2.13%), homozygous mutant S/S (15/15.96%) and C/C (1/1.06%), and mutant heterozygote S/C (4/4.26%). The proportions of genotypes varied between populations. Conclusion The kdr mutation rate is high in Ae. albopictus in Haikou. Local mosquito resistance should be further monitored, so that insecticides are used appropriately.