ISSN 1003-8280 CN 10-1522/R 中国疾病预防控制中心 主办
Objective To investigate the current infection status of scrub typhus and the risk factors for scrub typhus in Changping district of Beijing, China, and to provide a basis for the prevention and control strategies of scrub typhus. Methods The residents from 8 towns in Changping district were randomly selected to conduct a seroepidemiological survey from October to December, 2017. The risk factors for scrub typhus were analyzed. Independent chi-square test, stratified chi-square test, and trend chi-square test were used to analyze the infection rate between groups. Results A total of 480 serum samples were tested in this survey, of which 55 were positive for scrub typhus immunoglobulin G (IgG) antibody and the positive rate was 11.45%; there were significant differences in the positive rate between patients with different ages (χ2=57.712, P<0.001), education levels (χ2=35.257, P<0.001), and different occupations (χ2=17.222, P<0.001) and those in different regions (χ2=69.469, P<0.001). For farmers and serving officers, field work and walking or sitting on grass were risk factors for scrub typhus, respectively (odds ratio[OR]=3.03, 95% confidence interval[CI]:1.31-6.98; OR=3.18, 95%CI:1.07-9.46); spraying insect repellent and bathing or changing clothes after going out were protective factors, respectively (OR=0.45, 95%CI:0.21-0.98; OR=0.48, 95%CI:0.25-0.93). Conclusion The covert infection cases of scrub typhus are present in Changping district of Beijing, with significant population and regional differences, suggesting that it is necessary to strengthen surveillance, prevention, and control of scrub typhus and carry out further investigations.
Objective To investigate the distribution of mosquito vectors and prevalence of mosquito-borne diseases in the southwest border regions of Yunnan province, China, and to provide a basis for the prevention and control of such diseases. Methods From 2013 to 2015, the methods of mosquito lamp and human landing collection were used to collect mosquitoes in Dai-Lahu-Va Autonomous County of Menglian, Menghai, and Hani-Yi Autonomous County of Jiangcheng of Yunnan. A kit was used to extract DNA and RNA, and RT-PCR and nucleotide sequencing were used to obtain the gene sequence of pathogens. Biological software including Clustal X1.83, DNASTAR 7.1, and MEGA 5.0 were used for nucleotide sequence analysis and phylogenetic analysis. Results A total of 126 893 mosquitoes of 39 species in 10 genera were collected, among which there were 104 476 Culex tritaeniorhynchus mosquitoes (82.33%), 18 422 Anopheles sinensis mosquitoes (14.52%), 1 212 Aedes albopictus mosquitoes (1.00%), and 891 Cx. pipiens quinquefasciatus mosquitoes (0.70%). Two strains of Japanese encephalitis virus (JEV) were isolated from Cx. tritaeniorhynchus, and Plasmodium, filaria, and other flaviviruses were not detected. Conclusion There are various vector mosquitoes in the border regions of Yunnan. Cx. tritaeniorhynchus and An. sinensis are dominant species in the local area. The isolated JEV suggest that the virus be prevalen in the southwest border regions of Yunnan, and therefore, the monitoring of key vector mosquitos should be enhanced.
Objective To establish a set of standard techniques and methods for laboratory rearing of Triatoma rubrofasciata, and to provide a reference for understanding the life cycle and molecular biological characteristics of T. rubrofasciata, the diseases transmitted by T. rubrofasciata, and the prevention and control of these diseases. Methods Triatoma rubrofasciatawas artificially fed in an incubator with a constant temperature of (28±1)℃ and a relative humidity of (70±5)% under the laboratory condition of light for 12 hours and darkness for 12 hours. Kunming rats were used as the sole blood-feeding animal. Results Triatoma rubrofasciatacompleted the whole life cycle (126-153 days) under the artificial rearing condition. Stage I-V nymphs and adults all were fed with the blood of rats. Conclusion The reproduction of T. rubrofasciata is successfully carried out by laboratory rearing.
Objective To investigate the effects of ciprofloxacin hydrochloride on the individual growth and development and population reproduction of Musca domestica. Methods The newly laid eggs of M. domestica were placed on the filter paper soaped with 0.1%, 0.3%, and 0.5% ciprofloxacin hydrochloride or sterile water (control). The hatching rates of the eggs were observed. The hatched larvae were fed with 0.1%, 0.3%, and 0.5% ciprofloxacin hydrochloride or without ciprofloxacin hydrochloride (control). The development of M. domestica was observed every day and the developmental durations of egg stage, larval stage, and pupal stage were calculated. The male and female adults emerged from ciprofloxacin pupae and control pupae were paired. The ciprofloxacin adults were fed with brown sugar (nutrients) and sterile water with 0.1%, 0.3%, and 0.5% ciprofloxacin, while the control adults were fed with brown sugar (nutrients) and sterile water (control). The pre-oviposition period, number of eggs laid per female, and lifetime of adults were calculated. The age-stage, two-sex life table software was used to calculate the age-stage survival rate, fertility, number of eggs laid per female, intrinsic rate of increase, finite rate of increase, and net reproductive rate of M. domestica and to evaluate the effects of ciprofloxacin hydrochloride on the individual growth and development and population reproduction of M. domestica. Statistical analysis was performed using SPSS 20.0 software. Comparison between groups was made by one-way analysis of variance and comparison between two independent samples was made by the t test. Results The developmental durations of egg stage and pupal stage in 0.1%, 0.3%, and 0.5% ciprofloxacin groups were 1 day and 6 days, respectively. There were no significant differences in the durations of egg stage and pupal stage between the three ciprofloxacin groups and the control group (all P>0.05). The duration of larval stage in the control group and the three ciprofloxacin groups were 5.80±0.09 days and 8.44±0.06 days, respectively, and there was a significant difference in the duration of larval stage between the control group and the three ciprofloxacin groups (F=40.927, P=0.000). The lifetime of female adults and male adults in the control group vs the three ciprofloxacin groups were 28.39±0.92 days vs 17.19±0.85 days and 26.27±1.12 days vs 17.31±0.98 days, respectively, and there were no significant differences in the lifetime of female adults and male adults between the control group and the three ciprofloxacin groups (female:F=20.091, P=0.000; male:F=14.218, P=0.000). The pre-oviposition period of female adults and the number of eggs laid per female in the control group vs the three ciprofloxacin groups were 4.94±0.10 days vs 6.37±0.33 days and 638.76±39.32 vs 137.37±24.22, respectively, and there was a significant difference between the control group and the three ciprofloxacin groups (F=28.336, P=0.000). The age-stage, two-sex life table study showed that the hatching rates of M. domestica eggs, mortality rates in the whole life cycle, life expectancy of newly laid eggs, and life expectancy of female adults in the control group vs the three ciprofloxacin groups were 96.43% vs 68.75%, 15.48% vs 46.09%, 36.07 days vs 18.03 days, and 32.03 days vs 19.88 days, respectively. From the perspective of population ecology, the intrinsic rate of increase, finite rate of increase, and net reproductive rate in the control group vs the three ciprofloxacin groups were 0.23 vs 0.13, 1.26 vs 1.14, and 258.55 vs 28.98, respectively. Conclusion After feeding with ciprofloxacin hydrochloride, the individual development of M. domestica is retarded, fertility is decreased, and population growth rate is significantly inhibited.
Objective To preliminarily explore the infection status and molecular typing of Borrelia burgdorferi in rodents in parts of Fujian province. Methods Rodents were captured by the cage method in 5 counties (cities), i.e., Shaowu, Gutian, Shishi, Minhou, and Changle from April 2017 to June 2018. Nucleic acids were then extracted from rodent tissue samples (e.g., liver and kidney). After that, the fragments of 5S-23S rRNA were amplified by nested PCR, and sequencing results were analyzed by MEGA 6.0 software. Results A total of 192 rodents were captured, of which 81 were commensal rodents, accounting for 42.19% (81/192), and 111 wild rodents, accounting for 57.81% (111/192). Among all the rodents, four were detected to be positive for Lyme, accounting for 2.08% (4/192). Of the Lyme-positive rodents, one was commensal rodent, accounting for 1.23% (1/81) of all the commensal ones, and three wild rodents, accounting for 2.70% (3/111). Bioinformatics analysis revealed that SW14 from Shaowu and SS53 from Shishi were both B. valaisiana. The gene sequences of the two strains were identical or highly similar to those of B. valaisiana isolate R48 (EU160458.2) and B. valaisiana isolate 11 (JX888445.1), respectively. The gene sequences of both the SW15 from Shaowu and the GT38 from Gutian were different from those of above-mentioned B. valaisiana. Conclusion Rodents carry B. burgdorferi in the five surveyed counties (cities). The genotype (i.e., B. valaisiana) is consistent with that in the surrounding provinces.
Objective To investigate the resistance status of Blattella germanica, Aedes albopictus, and Musca domestica to commonly used insecticides in Jiaxing, and to provide a scientific basis for the development of reasonable and effective prevention and control measures. Methods The residual film was used to determine the median knockdown time (KT50) of propoxur, beta-cypermethrin, dimethyl dichloro-vinyl phosphate (DDVP), deltamethrin, and acephate against B. germanica. The WHO standard test kits were used to measure the mortality of Ae. albopictus at diagnostic doses of propoxur, beta- cypermethrin, deltamethrin, permethrin, and malathion. Micro-topical application was used to determine the median lethal doses (LD50) of propoxur, beta-cypermethrin, DDVP, deltamethrin, and permethrin against M. domestica. Results Blattella germanica showed moderate resistance to deltamethrin and DDVP, with resistance ratios of 8.21 and 5.33, respectively, showed low resistance to beta-cypermethrin, with a resistance ratio of 4.31, and was sensitive to propoxur and acephate, with resistance ratios of 1.58 and 1.05, respectively. The mortality rates of Ae. albopictus to beta-cypermethrin, deltamethrin, and permethrin were 100%, 100%, and 98.67%, respectively, indicating that Ae. albopictus was sensitive to these insecticides. However, its mortality rates to malathion and propoxur were 97.33% and 90.67%, respectively, suggesting possible resistance. Musca domestica demonstrated moderate resistance to DDVP (resistance ratio:10.47), low resistance to deltamethrin (8.22) and permethrin (8.13), and sensitivity to propoxur and beta-cypermethrin. Conclusion As shown from the resistance criteria, B. germanica, Ae. albopictus, and M. domestica in Jiaxing have different degrees of resistance to commonly used insecticides. Therefore, surveillance of insecticide resistance should be highlighted for rational use of insecticides.
Oncomelania hupensis is the only intermediate host of Schistosoma japonicum, and chemical control of the snails is an effective means to control the spread of schistosomiasis. Current research findings have shown that the mechanism of chemical control of the snails mainly includes the following aspects:(1) to cause nervous system dysfunction in O. hupensis by affecting the activities of key enzymes involved in nerve signal transduction and transmission, including acetylcholinesterase and nitric oxide synthase, thus leading to death; (2) to cause disorders in energy metabolic pathways in O. hupensis by affecting the activities of enzymes involved in glucose metabolism and energy supply, including succinodehydrogenase and lactate dehydrogenase, thus leading to death; (3) to cause disorders in the liver defense system and even liver failure by affecting the activities of enzymes involved in liver detoxification function, including aminotransferases, phosphatase, and esterase isozyme, thus leading to poisoning and death. With a focus on the influence of molluscicides on the ultrastructure of vital organs including the liver and the activities of various key enzymes, this article elaborates on the mechanism of action of molluscicides in eliminating Oncomelania snails, in order to provide a reference for research and development of new molluscicides.
