ISSN 1003-8280 CN 10-1522/R 中国疾病预防控制中心 主办
Objective To investigate the effects of high-temperature water treatment in different larval stages on the body size, body weight, and sex ratio of adult Aedes aegypti and to determine the critical stages when high water temperature exerts significant effects on the above indices. Methods Ae. aegypti larvae of different instars (including egg stage and the first to fourth instars) were divided into experimental group and control group. The larvae in experimental group were kept in a water bath (36℃) till they developed to the next instar, and then the living larvae were moved to the insectariums with normal condition[temperature, (25±1)℃; humidity, (75±5)%] and reared conventionally. After eclosion, the numbers of female and male mosquitoes were recorded, and the wing length and body weight were measured after they were dried in an oven (60℃) for 15 min. The larvae in control group were reared conventionally in the insectariums to get the standard values. Results For Ae. aegypti larvae of the second to fourth instars in experimental group, their female adults had wing lengths significantly lower than the standard value. For Ae. aegypti larvae of the second and fourth instars in experimental group, their female adults had decreased body weights, but the decrease was not significant for the larvae in the egg stage, first instar, and third instar. For Ae. aegypti larvae of the third and fourth instars, their adults had male/female ratios of 0.88:1 and 0.95:1, while the ratio was 2.43:1 for the larvae of the second instar. Conclusion The effects of high-temperature water treatment on Ae. aegypti vary depending on the larval stage; the larvae in the egg stage and first instar are less sensitive to the high water temperature than those in the second to fourth instars. The second instar is a critical stage for the development of female Ae. aegypti, and the third instar is a critical stage for the development of male Ae. aegypti.
Objective To investigate the effect of joint use of repellent and attractant for mosquito control in the field and to evaluate the specific attraction of octanoic acid, indole, and CO2 mosquito trap for mosquitoes. Methods Six sites in Taiping village, Yingjiang county, Yunnan province, China were selected for field test. In the first to fourth sites, rosemary essential oil as a repellent was hung at the center, and a CO2 mosquito trap combined with octanoic acid and indole was placed 1, 5, 10, 15 or 20 m from the rosemary essential oil. In the fifth site, only a CO2 mosquito trap was placed at the center. The mosquitoes captured by the CO2 mosquito trap were counted and classified every day, and the obtained data were subjected to statistical analysis. Results Joint use of repellent and attractant at an appropriate spacing captured significantly more mosquitoes than use of attractant alone (ANOVA, P<0.05). A total of 594 mosquitoes were captured in 3 tests at the third site (10 m between the rosemary essential oil and CO2 mosquito trap), most among the 5 sites (P=0.036). The number of mosquitoes captured by the CO2 mosquito trap combined with octanoic acid and indole was 30% more than that of mosquitoes captured by the CO2 mosquito trap alone in each of 3 tests. Aedes mosquitoes accounted for about 80% of all captured mosquitoes, and Ae. alboscutellatus, Ae. albopictus, Ae. craggi, and Ae. desmotes were the dominant species in this region. Conclusion Joint use of repellent and attractant at an appropriate spacing can capture more mosquitoes than CO2 mosquito trap alone and can be used in mosquito control. CO2 mosquito trap combined octanoic acid and indole shows some specificity for Aedes and can be used in the surveillance of Aedes vector mosquitoes.
Objective To analyze the pulsed-field gel electrophoresis (PFGE) band patterns of pathogenic Yersinia enterocolitica from live pigs in Chinese abattoirs and to provide a basis for the control of Y. enterocolitica. Methods Pharyngeal swabs (tonsils) and intestinal contents (at the ileocecal junction) were collected from the pigs in abattoirs in 11 provincial regions of China; Y. enterocolitica was isolated from the obtained specimens, and the pathogenic strains were analyzed by PFGE. Results The pathogenic strains of Y. enterocolitica were subjected to PFGE typing. The 763 pathogenic strains of Y. enterocolitica serotype O:3 were classified into 47 patterns after cleavage with NotⅠ, and 431 (56.49%) of the 763 strains had the band pattern of K6GN11C30021; another serotype O:9 strain had the band pattern of K6GN11C90004. Two or more PFGE patterns were found in each abattoir, including dominant and common PFGE patterns. Conclusion There are diverse PFGE patterns of pathogenic Y. enterocolitica among the live pigs in Chinese abattoirs, with some regional characteristics, and the Y. enterocolitica with different PFGE patterns can be simultaneously carried in the pharyngeal region and the intestinal contents at the ileocecal junction. Measures should be taken to prevent Y. enterocolitica carried by pigs from contaminating pork and its products and polluting the environment and to protect public health and ensure food safety.
Objective To detect pesticin (Pst) antibody in the sera of plague host animals and to investigate the feasibility of using Pst as the diagnostic reagent in plague antibody detection. Methods A total of 351 serum samples of plague host animals from different sources were subjected to indirect enzyme?linked immunosorbent assay (ELISA) for detection of recombinant Pst antibody and F1 antibody. Results Pst antibody was found in the serum samples of plague host animals, and the serum level of Pst antibody increased significantly as the serum level of F1 antibody rose. The ELISA absorbance value was 0.438 in plague patients 20 months later, and the Pst antibody in serum remained at a detectable level. Conclusion Pst antibody detection can be used along with F1 antibody detection, so as to make plague antibody detection more reliable.
Objective To develop cross priming amplification (CPA) technology for rapid, sensitive, and specific detection of Plasmodium falciparum. Methods The CAP primers and probes were designed based on the conserved 18S rRNA sequence of P. falciparum. The blood samples of 78 patients with fever were examined by CPA and Giemsa staining microscopy, and the specificity and sensitivity of CPA method were evaluated. Results P. falciparum was detected by CPA method in 37 of 38 P. falciparum-containing blood samples, and other pathogens were not detected by this method, suggesting that CPA method has high specificity for P. falciparum. The sensitivity of CPA method was 102 copies/μl. The specificity, sensitivity, and accuracy of CPA method were 97.37%, 100%, and 98.72%, respectively, as compared with those of microscopic examination. Conclusion CPA assay is a simple, rapid, sensitive, and specific method for detecting P. falciparum in the clinical setting and at entry-exit ports.
Objective To investigate the feasibility of blood clotting response (BCR) test for determining the resistance to anticoagulant rodenticide in Rattus losea. Methods Sensitive and resistant populations of R. losea were screened out by a single gavage of warfarin at a discriminating dose of 10 mg/kg and lethal feeding period test. Plasma was collected from test rats at different time points; the standard curve of BCR was established by measuring the percentage clotting activity (PCA) of plasma, and the difference in PCA between resistant and sensitive individuals treated with a discriminating dose of warfarin was analyzed. Results The standard curve of BCR in R. losea was established as follows: INR(y)=34.984/x+0.688(x=PCA)(R2=0.992). After the single gavage of warfarin at a discriminating dose of 10 mg/kg, the PCA of resistant individuals decreased, but it was restored to 17% of normal level within 2-3 d; the PCA of sensitive individuals decreased dramatically and was not restored. Conclusion This study confirms the feasibility of BCR test for determining the resistance to anticoagulant rodenticide in R. losea. It is accurate and simple to differentiate resistant and sensitive individuals of R. losea by a single gavage of warfarin (10 mg/kg) and using PCA=16.5 (or INR=4.4) as the threshold 4 d later.
Objective To determine the resistance to the first-generation anticoagulant rodenticide in Rattus losea in the farmlands of Guangzhou city, China and investigate their avoidance behavior to poison bait or nontoxic bait, and to provide a basis for rodent control. Methods The resistance of R. losea was determined using the method established by Rodenticide-resistance Monitoring Cooperation Group in China. The avoidance behavior was studied by successive poison bait supply experiments. Results The percentage of R. losea which developed resistance to the first-generation anticoagulant rodenticide reached 83.33% in Guangzhou. Evident avoidance behavior to warfarin bait was seen in R. losea, and the bait shyness rate reached 30.00%. In the successive poison bait supply experiments and nontoxic bait supply experiments for rodent that survived after resistance determination, the poison bait shyness rate deceased generally in each experiment, but there was no significant change in the avoidance behavior to nontoxic bait. As the time of poison bait supply increased, the proportion of R. losea individuals with bait shyness rose, and the degree of nontoxic bait shyness was even higher than that of poison bait shyness in the first poison bait supply experiment. The daily intake of poison bait also deceased significantly, and the daily intake was still lower than those in the first and second poison bait supplies when R. losea was given nontoxic bait after the poison bait supply experiments. Conclusion The avoidance behavior of R. losea in Guangzhou to poison bait and even nontoxic bait indicates that R. losea has developed resistance to the first-generation anticoagulant rodenticide, which would be a big challenge to rodent control. This study provides an important guidance for improving rodent control effect.
Objective To investigate the major species of rodent pests in the livestock and poultry farms (pig farms, cattle farms, and chicken farms) in Beijing, China and the seasonal population variations in the rodent pests, and to provide a reference for rodent pest control. Methods The species and density of rodent pests were monitored monthly from August 2010 to July 2011 in 9 livestock and poultry farms in Fangshan district, Pinggu district, and Shunyi district, Beijing. In each farm, traps baited with peanuts were set to capture rodent pests at night. Results There were 21 600 trap-times throughout the year, and 236 rodents including Mus musculus and Rattus norvegicus were captured. The farms were affected by rodent pests more seriously in autumn (September to November) and winter (December to February) than in other seasons, and 54.4% and 31.6% of all rodent pests were captured in autumn and winter, respectively; the highest population density of rodents was seen in October. Throughout the year, there was alternate population variation between M. musculus and R. norvegicus; the sex ratios of M. musculus and R. norvegicus populations were 1.63 and 0.71, respectively. Conclusion Autumn (September to November) is the key period for rodent pest control in the livestock and poultry farms in Beijing.
Objective To study the community structure and diversity of mites breeding in tobacco storage in Anhui province, China. Methods Samples (tobacco leaves and tobacco dust on the ground) were obtained from four different habitats (simple storage, open storage, tenemental storage, and alcoholizing storage) of tobacco storage, and mites were collected, isolated, identified, counted, and analyzed. Results Twenty-three species of mites belonging to 16 genera and 5 families were collected. The species number, species richness, and species diversity of mites were the highest in simple storage, followed by open storage, tenemental storage, and alcoholizing storage. The species evenness of mite community was the highest in simple storage (J'= 0.959), while the species domination of mite community was the highest in alcoholizing storage (D=0.150). The Jaccard similarity index between the mite communities in open storage and alcoholizing storage was the lowest (Q=0.238). Conclusion The community structure and diversity of mites breeding in tobacco storage in Anhui province are closely related to the habitat conditions, and there are relatively few mites breeding in alcoholizing storage.
Objective To study the relationship between vegetation attributes and distribution of Oncomelania hupensis on the beach of Qingyi River. Methods Using a combination of random sampling and systematic sampling, an investigation was conducted on the vegetation and O. hupensis in the quadrats on the beach of Qingyi River to determine the species, cluster number, phenological period, viability, height, coverage, abundance, and frequency of vegetation as well as the total number of snails, number of living snails, and number of dead snails. Results There were 12 major species of vegetation on the river beach, including Alternanthera philoxeroides, Cynodon dactylon (Linn.) Pers., Cyperus microiria, Torilis scabra (Thunb.) DC., Artemisia lavandulaefolia DC., Dendranthema indicum (L.) Des Moul., Xanthium sibiricum, Rhizoma cyperi, Humulus scandens (Lour.) Merr., Juncus effusus, Glycine soja Sieb. et Zucc., and Polygonum flaccidum Meissn.; A. philoxeroides and Rhizoma cyperi were the dominant species. The density of living snails was the highest in the A. philoxeroides cluster (2.67 living snails/0.1 m2), and the density of dead snails was the highest in the C. dactylon/P. flaccidum cluster (2.33 dead snails/0.1 m2). The regression analysis of vegetation coverage and O. hupensis density produced the following quadratic functions: y=11.435+2.104x-0.162x2 (R2=0.394,F=42.319,P<0.01) (summer); y=14.154+1.034x-0.043x2 (R2=0.794,F=57.432,P<0.01) (autumn). Conclusion O. hupensis has a tendency toward the A. philoxeroides cluster, and the C. dactylon/P. flaccidum cluster may have a molluscicidal effect on O. hupensis. The relationship between coverage of vegetation and density of O. hupensis can be reflected by quadratic functions.
Objective To investigate the community structure and diversity of acaroid mites breeding in different habitats including human habitat, working environment, and storage habitat in northern Anhui province, China. Methods Acaroid mites were isolated by direct microscopy and water flotation and then counted and identified; the obtained data were analyzed. Results Acaroid mites were isolated from 416 of 720 samples, with a positive rate of 57.78%, including 41 species belonging to 20 genera and 7 families; Tyrophagus putrescentiae was the dominant species. The species number, species richness, and species diversity of acaroid mites were higher in the storage habitat than in the working environment. The species evenness was higher in the working environment than in the human habitat. Conclusion There are many species of acaroid mites in northern Anhui province, and they breed heavily in this area. The habitat condition directly influences the community structure and diversity of acaroid mites.
Objective To investigate the resistance levels of Musca domestica to four commonly used insecticides in the special places such as landfill and meat processing plant in Guangdong province, China. Methods M. domestica larvae were collected in the wild breeding habitats, and topical application was used to determine the median lethal doses (LD50) of permethrin, deltamethrin, beta-cypermethrin, and DDVP for M. domestica. The experimental data were statistically analyzed by extremum method. Results The LD50 of permethrin, deltamethrin, beta-cypermethrin, and DDVP were 13.7179, 3.5971, 5.5982, and 0.7704 μg/insect, respectively, for M. domestica in the landfill and were 1.0999, 0.7278, 8.3314, and 0.5322 μg/insect, respectively, for M. domestica in the meat processing plant. The resistance ratios were 58-2525, increased 1-103 times compared with those in 1996 and increased 2-1383 times compared with those in 1991. The resistance of M. domestica to permethrin, deltamethrin, and DDVP was higher in the landfill than in the meat processing plant. Conclusion M. domestica develops high resistance to some insecticides in the special places in Guangdong province, and the resistance to pyrethroid increases rapidly. Comprehensive management strategies and proper insecticide use should be adopted to control M. domestica in the special places such as landfill and meat processing plant.
Objective To investigate the breeding habitats and seasonal population fluctuation of Aedes albopictus at Yunfu port, Guangdong province, China and to observe the effect of mosq-ovitraps applied at the port. Methods Various water containers were examined carefully to record the types of containers and whether Ae. albopictus larvae bred in the containers. The seasonal population fluctuation of Ae. albopictus was monitored by labor-hour method in typical habitats. Mosq-ovitraps were set to monitor the seasonal fluctuation in container index (CI) of Ae. albopictus larvae. Results There were 569 water containers detected, 76 of which contained Ae. albopictus larvae, with a mean CI of 13.36%. The water containers at Yunfu port were mainly waste tires, and those in households mainly included waste buckets, pots, and reservoirs. The population density of Ae. albopictus peaked from mid-May to August. A total of 1620 mosq-ovitraps were set from June to November in 2011, and oviposition was found in 151 of them, with a mean oviposition index (OI) of 9.41%. The OI peaked from June to September. Conclusion The breeding habitats and seasonal population fluctuation of Ae. albopictus at Yunfu port are acquired in the study. This information provides a scientific basis for Ae. albopictus control and essential data for setting of mosq-ovitraps at the port.
Objective To investigate the epidemiological characteristics of hemorrhagic fever with renal syndrome (HFRS) in Hebei province, China in 2011 and analyze the surveillance data and to provide a scientific basis for the control of HFRS. Methods The epidemic data of HFRS were collected. The density and virus-carrying rate of rodents at each surveillance site was recorded. PCR genotyping was performed using the positive lungs of rodents. Results In 2011, 513 cases of HFRS including one death were reported in Hebei province, with an incidence rate of 0.71/105 and a fatality rate of 0.20%. These cases were distributed in 74 counties (cities, districts), mostly in Qinhuangdao city and Tangshan city, in Hebei. The peak seasons were in spring and winter. The percentage of cases occurring from March to June was 42.50%, and 205 cases (30.02%) occurred from October to January of the next year. Of all cases, 364 (70.96%) were aged 20-59 years. The male-to-female ratio was 2.72:1. Peasants amounted for 78.36% of all cases. The rodent density in residential area was 2.04%, and the virus-carrying rate was 7.41%; the rodent density in the field was 0.64%, and the virus-carrying rate was 0. The dominant species of rodents in the residential area and field was Rattus norvegicus. The PCR genotyping using positive lungs showed that all belonged to Rattus type (type Ⅱ). Conclusion Hebei province is a mixed epidemic area of HFRS, mostly of Rattus type. We should enhance comprehensive control of HFRS with an emphasis in the 9 counties (districts) with high incidence of HFRS.
Objective To update the information on the species of ectoparasitic fleas on small mammals in Gonghe county, Qinghai province, China. Methods Small mammals were captured by night trapping method, and ectoparasitic fleas were collected from them. The slide specimens of fleas were made, and these fleas were classified and identified based on morphological characteristics. Results A total of 785 ectoparasitic fleas (13 species, 8 genera, 3 families) were collected from small mammals in Gonghe county. Conclusion Neopsylla bidentatiformis (Wagner, 1883) is a new record in Qinghai province.
Objective To investigate the infection with Borrelia burgdorferi sensu lato and its genospecies in Pingxiang of Guangxi Zhuang Autonomous Region, China. Methods The specimens of ticks, rodents, and wild birds were collected in Pingxiang region of Guangxi Zhuang Autonomous Region in July 2011. Genomic DNA of B. burgdorferi sensu lato was extracted from the ticks and the spleens of rodents and wild birds by boiling method and Qiagen kit. The 5S-23S rRNA gene intergenic region of B. burgdorferi sensu lato was amplified by nested PCR; the PCR products were sequenced and aligned with the sequences of 5S-23S rRNA gene intergenic region of B. burgdorferi sensu lato deposited in GenBank to identify the genospecies of B. burgdorferi sensu lato. Results B. burgdorferi sensu lato was detected in three rodent specimens, with an infection rate of 5.66% (3/53) among the rodents. One of the sequences had a homology of 100% with B. valaisiana (accessions in GenBank: HM100125.1, AB091455.1, AB091454.1, AB091453.1). B. burgdorferi sensu lato was not found in ticks and birds. Conclusion The infection with B. valaisiana in rodents is present in Pingxiang region of Guangxi Zhuang Autonomous Region.
Objective To investigate the species and distribution of ticks in Tianjin, China, the pathogens carried by the ticks, and the knowledge of self-protection against ticks in local residents, and to provide a basis for the control and prevention of ticks. Methods The specimens of ticks were collected with white cloth from the natural habitat and picked directly from the body surfaces of livestock such as cattle and sheep. The specimens were identified and classified and subjected to detection of carried pathogens, such as Bunia virus, Borrelia burgdorferi, Bartonella, and Anaplasma phagocytophilum. Twenty residents were randomly selected from each district or county of Tianjin and the knowledge of self-protection against ticks was surveyed. Results Ticks were found in 8 districts or counties of Tianjin. A total of 152 ticks were collected and identified, including Ixodes persulcatus (23.03%) and Haemaphysalis longicornis (76.97%). No pathogen was detected from the tick specimens. More than 70% of the surveyed residents had the knowledge of tick bite prevention, and over 80% of the surveyed residents had the knowledge of correct treatment after bite, without significant difference between urban and rural residents. Conclusion There are ticks in Tianjin, and no pathogen is found from the tick specimens. Most residents have the knowledge of self-protection against ticks. More measures should be taken to enhance the control and prevention of tick-related diseases, including spreading tick-related knowledge among residents, improving the ability of health care sector to control and prevent tick-related diseases, and making related emergency plans.
Objective To investigate the current situation of plague vectors in the Meriones unguiculatus plague foci on the Inner Mongolian Plateau and to provide a basis for scientific control of M. unguiculatus plague. Methods The 2000-2011 data on plague vectors in the M. unguiculatus plague foci on the Inner Mongolian Plateau were collected and then subjected to statistical analysis. Results In 2000-2011, 96 411 fleas (24 040 groups) were detected, including 1657 positive fleas (533 positive groups), with a positive rate of 1.72% (group positive rate, 2.22%). Conclusion Animal plague is prevalent in the M. unguiculatus plague foci on the Inner Mongolian Plateau, which is one of the animal plague-affected areas with the highest epidemic strength in China. Flea plays an important role in human plague epidemic in Inner Mongolia. Long-term systemic surveillance should be conducted in the plague foci to effectively control the occurrence and prevalence of human plague.
Objective To investigate the species composition of mosquitoes and the diurnal variations in numbers of dominant species of mosquitoes on the Heixiazi Island in Fuyuan county, Heilongjiang province, China. Methods Mosquitoes were collected using the human-baited net trap, light trap, and insect net. Results A total of 33 526 mosquitoes belonging to 4 genera and 10 species were collected on the Heixiazi Island. The dominant species was Aedes vexans (94.68%). The species composition varied in different months. The diurnal variations in numbers of 4 dominant species of mosquitoes were as follows: Ae. vexans was active in a whole day, Ae. sticticus during the 3rd to 21st hour of day, Culex modestus during the 6th to 20th hour, and Anopheles sinensis during the 3rd to 19th hour; the activity peak occurred at the 3rd and 20th hours for Ae. vexans, at the 17th hour for Cx. modestus, at the 18th hour for Ae. sticticus, and at the 21st hour for An. sinensis. Conclusion The mosquitoes on the Heixiazi Island were composed of 4 genera and 10 species, and the dominant species was Aedes vexans, and the diurnal-variation-number of the four dominant species was observed.
Objective To investigate the species of mosquitoes and mosquito-borne arboviruses in Haikou, Hainan province, China, and to provide a scientific basis for the prevention and control of mosquito-borne diseases. Methods Mosquito samples were collected using electric mosquito traps in Haikou city and other four districts (with different habitats) from June to November in 2010; the mosquito samples were classified in the laboratory, and viruses were isolated from them and then identified. Results A total of 8425 mosquitoes were captured. Of all these mosquitoes, 68.87% were Culex tritaeniorhynchus, 20.21% were Cx. pipiens quinquefasciatus, 6.64% were Anopheles sinensis, and 4.28% were Armigeres subalbatus. One strain of Getah virus and one strain of Banna virus were isolated from the mosquito samples. Conclusion The prevention and control of mosquitoes should be carried out according to the ecological characteristics of mosquitoes in Haikou, so as to effectively prevent mosquito-borne infectious diseases.
Objective To investigate the species, distribution, and density of dominant species of rodents and parasitical fleas and the infections of rodents with Yersinia pestis and hantavirus (HV) in Jixian of Tianjin, China, and to provide a basis for effective prevention and control of plague and hemorrhagic fever with renal syndrome (HFRS). Methods Cages were used to capture rodents. The captured rodents and the fleas collected from the rodents were classified and identified, and the density of rodents and flea-carrying rate were calculated. Indirect hemagglutination assay was used to detect the Y. pestis F1 antibody. Polymerase chain reaction was used to identify the specific genes of Y. pestis (fra and pla). Fluorescent antibody technique was used to detect HV antigen in rodent lungs (HFRS Ag). Results From April to September in 2011, 269 rodents (8 species, 7 genera, and 3 families) were captured in Jixian of Tianjin, and the density of rodents was 1.15%; 9 fleas (Monopsyllus anisus) were collected from the rodents; the flea-carrying rate was 3.68%, and the total flea index was 0.055. A total of 188 serum samples of rodents were collected, and no Y. pestis F1 antibody was detected. A total of 247 liver samples of rodents were collected, and the specific genes of Y. pestis were not detected. A total of 89 lung samples of rodents were collected, and HV antigen was detected in one sample, with a positive rate of 1.12%; the HV was confirmed as Seoul virus (SEOV). Conclusion R. norvegicus is the dominant species of rodents in Jixian of Tianjin. Both the rodent density and flea index are lower than the standard precaution level for plague control, and no rodent plague epidemic is found. R. norvegicus is the major host animal of HFRS, from which SEOV is detected.
Objective To investigate the resistance of Blattella germanica to commonly used insecticides in passenger train and station and provide a basis for the control of B. germanica in passenger train and station. Methods The residual film method recommended by WHO was used to measure the resistance of B. germanica to commonly used insecticides. B. germanica was placed in the jars with residual films; the knockdown rates and resistance ratios were calculated. Results The resistance ratios of B. germanica were 143.96-171.49 for deltamethrin, 10.25-118.18 for beta-cypermethrin, 18.58-135.08 for cypermethrin, 18.14-34.31 for permethrin, 4.08-5.11 for lambda-cyhalothrin, 1.91-2.50 for dichlorvos, 2.13-2.45 for propoxur, 1.20-1.65 for chlorpyrifos, and 1.48-3.62 for fenobucarb, respectively. Conclusion B. germanica has developed different levels of resistance to deltamethrin, beta-cypermethrin, cypermethrin, permethrin, and lambda-cyhalothrin, so the most suitable insecticide should be selected according to the resistance levels to effectively control B. germanica in passenger train and station.
Objective To investigate the insecticide resistance of Musca domestica in recent years and the resistance of Chrysomya megacephala to several common insecticides in Shenzhen, China, and to provide a scientific basis for the control of flies. Methods M. domestica and C. megacephala were collected in the urban area of Shenzhen and raised in the laboratory for 1-2 generations. Topical application was used to determine the median lethal doses (LD50) (μg/insect) of deltamethrin, beta-cypermethrin, permethrin, tetramethrin, DDVP, and fenobucarb for M. domestica and C. megacephala. Results For M. domestica, the LD50 of deltamethrin, permethrin, tetramethrin, DDVP, and fenobucarb were 0.024 819, 0.092 076, 0.649 075, 0.065 610, and 5.008 337 μg/insect, respectively, increased by 8.27, 7.25, 3.45, 0.11, and 0.54 times compared with the resistance monitoring data in 1998. For C. megacephala, the LD50 of deltamethrin, beta-cypermethrin, permethrin, tetramethrin, DDVP, and fenobucarb were 0.271 852, 0.318 642, 0.174 697, 0.657 885, 0.086 490, and 1.743 459 μg/insect, respectively. Conclusion The resistance of M. domestica to deltamethrin, permethrin, and tetramethrin increases slowly, while its resistance to DDVP and fenobucarb exhibits a declining trend. The results of resistance test for C. megacephala are different from those for M. domestica, and it is necessary to improve experimental methods and establish the standard for resistance levels.
Objective To determine the species of a large number of phoretic mites on the body surfaces of Muscina stabulans in Changping district of Beijing, China, and to provide a basis for scientific prevention and control measures. Methods A canopy-type fly-trapping cage was used to capture flies for 6 h; insecticide was sprayed to the cage; the cage was covered with a white plastic bag, and the bag was closed and brought back to the laboratory. Mites were collected from the body surfaces of flies and from inside the bag and then observed under a light microscope and scanning electron microscope; the mites were identified by observation and consultation with reference materials. Results Two species of mites were identified, including Macrocheles muscaedomesticae and hypopus of Anoetidae. Conclusion Vector surveillance should include monitoring of phoretic mites, so as to improve the monitoring system.
Objective To investigate the community structure and density of small mammals in the natural environment in Mentougou district of Beijing, China and to detect the infection with Yersinia pestis in the mammals. Methods The surveillance was conducted from 2009 to 2011. Small mammals were captured by trap-at-night method. The rodent species were identified, and the capture rate was calculated. Living rodents were captured by cage-trap method, and blood samples were collected from the heart for detection of F1 antibody of Y. pestis. Results A total of 315 small mammals (7 species) were captured in Mentougou district from 2009 to 2011, including 309 mammals (6 species) of the order Rodentia and 6 mammals (1 species) of the order Insectivora. The capture rates of small mammals were 16.60%, 4.62%, and 15.08%, respectively for different year. The three species of rodents with the highest capture rate and constituent ratio were Apodemus peninsulae, Niviventer confucianus, and A. agrarius; the total proportions of the three rodents were 95.18%, 88.89%, and 96.84% from 2009 to 2011. In the serological detection, no Y. pestis F1 antibody was found in 49 blood samples. Conclusion No infection of Y. pestis has been found by serological detection in rodents in Mentougou district of Beijing, and there is no natural foci of plague in this area.
Objective To observe the control effects of 10% boric acid gel bait on cockroaches in the laboratory and field and compare it with residual spray in killing cockroaches. Methods The killing effects of 10% boric acid gel bait and residual spray were observed in the laboratory and simulated field according to the national standards GB/T 17917.7-2009 and GB/T 17917.10-2009. The decrease in cockroach density was determined by visual measurement after residual spray and application of gel bait in the field, and the killing effect was evaluated accordingly. Results In the laboratory and simulated field, all Blattella germanica died 2 d after treatment. In the field, the average density of B. germanica was 169.25/15 min before residual spray; the density decreased by 9.60% and 6.29% in the first and second weeks after residual spray of 10% cis-cypermethrin suspoemulsion plus 80% DDVP; then, residual spray of 10% cis-cypermethrin emulsion plus 20% propoxur EC was performed, and the density decreased by 6.63% and 5.51% in the third and fourth weeks. Finally, 10% boric acid gel was used, and the average density of B. germanica decreased by 94.10% and 100% in the first and second weeks after treatment. The average density of B. germanica was 1.38/15 min 1 month later. Conclusion The B. germanica population with high insecticide resistance is difficult to be control by residual spray, but 10% boric acid gel bait has good control effect on cockroaches and causes little insecticide resistance. Gel bait is recommendable for cockroach control.
Objective To analyze the distribution and variation of Leptospira in humans and host animals after leptospirosis outbreak and to provide a scientific basis for prevention of leptospirosis. Methods Sera of clinically diagnosed patients and host animals were collected and examined by microscopic agglutination test (MAT). The kidney samples of rodent, frog, pig, and teal as well as the midstream urine samples of cattle were collected; pathogens were isolated from the samples and then cultured, and the strains were identified by MAT. Results Five cases of leptospirosis were reported in Pan'an county from 2009 to 2012. A total of 40 duck sera were examined, and 8 were positive for antibodies against Leptospira, including 6 cases for antibody against strain 56601 and 2 cases for antibody against strain 56608. A total of 439 small mammals were examined, and 14 strains of Leptospira, all of which were strain 56601, were isolated. No Leptospira was detected in the kidney samples collected from 80 duck, 390 frog, 244 pig, and 160 cattle midstream urine samples. Conclusion Leptospira is prevalent in host animals in Pan'an county, and the epidemic strains in foci may change. Surveillance should be enhanced to prevent leptospirosis.
Objective To investigate the epidemiological characteristics of Japanese encephalitis (JE) and its risk factors in Zhoukou city, Henan province, China from 2004 to 2011, and to provide a scientific basis for JE control. Methods The JE case data and surveillance data in Zhoukou during 2004-2011 were analyzed by descriptive epidemiological method. Results A total of 291 JE cases were reported in Zhoukou during 2004-2011, with an average annual incidence of 0.36/105; from 2004 to 2011, the annual incidence rates were 0.41/105, 0.42/105, 0.78/105, 0.52/105, 0.17/105, 0.35/105, 0.25/105, and 0.03/105, respectively. The incidence rate was the highest in Taikang county (0.63/105) and the lowest in Xihua county (0.15/105). The peak season of JE was from July to September, when 96.22% of all cases occurred. Among the 291 JE cases, 97.25% were aged under 15 years, 17.18% were preschool children, 48.80% were scattered children, and 33.33% were students. Of the 267 surveyed cases, 219 (82.02%) had no anti-mosquito measures, such as mosquito nets and drugs, used at home, and 232 (86.89%) had not been immunized with JE vaccine. Conclusion The incidence of JE fluctuated but decreased in Zhoukou from 2004 to 2011. Enhancing monitoring of JE cases, ensuring vaccinization among children under 15 years of age in high-prevalence area, and taking comprehensive anti-mosquito measures are key to reducing the incidence of JE.
This paper first analyzes the epidemic characteristics of zoonotic plague in foci with respect to the epizootic activity of plague natural foci in China and then reviews the progress in research on plague natural foci, including hidden state of foci and changes in zoonotic plague epidemic situation caused by Yersinia pestis mutation, from the perspective of natural focal disease. This paper proposes the intervention measures for plague natural foci in the densely populated area, e.g., eliminating plague natural foci through comprehensive prevention and control means in the following steps: relative isolation, basic stabilization and control, long-term resting, gradual decrease in area, and elimination.
