Comparative analysis of Aedes albopictus surveillance index in Yangpu District， Shanghai / 上海预防医学

ObjectiveTo analyze the interannual fluctuation， seasonal fluctuation， habitat distribution and the correlation of the 3 monitoring indicators of Aedes albopictus in Yangpu District of Shanghai from 2017 to 2021， and to provide a scientific basis for A. albopictus control and rational use of the indicators. MethodsThe density surveillance data of A. albopictus recorded by Breteau index （BI）， Path index （PI） and the mosquito ovitrap index （MOI） from 2017 to 2021 in Yangpu District， Shanghai were compared. Microsoft Excel 2019 software was used for data summary and SPSS 25.0 software was used for statistical analysis. ResultsFrom 2017 to 2021， there were two months with BI>5， and the PI were all above the density control level of Class C， and there were nine months with MOI≥5. In 2017， BI was higher than in the other four years， with statistically significant differences （all P≤0.001）. MOI in 2017 and 2020 was higher than in 2019 （P=0.029， P=0.004） and 2021 （P=0.005， P=0.001）， with statistical significance. MOI for different types of habitats varied significantly， with a statistically significant difference （P=0.004）. A linear correlation was observed between BI and PI （r=0.462， P=0.010）. ConclusionBI， PI and MOI are used simultaneously to reflect the density of A. albopictus in Yangpu District of Shanghai. However， these three monitoring indicators show poor linear correlation. Comprehensively considering the scientific aspects of monitoring methods and seasonal fluctuations of indicators， it is suggested that MOI should be used as the main index to evaluate the density of A. albopictus. In the MOI， attention should be paid to factors such as the distribution of the habitats， the standardization of operating methods， and quality control， which are essential for enhancing the reliability of the MOI.

Surveillance of Aedes populations in Jiangsu Province in 2020 / 中国血吸虫病防治杂志

Objective To investigate the seasonal Aedes population fluctuation and the resistance of Aedes populations to common insecticides in Jiangsu Province in 2020, so as to provide insights into vector-borne infectious diseases control.. Methods One village was randomly sampled from each of Xinbei District of Changzhou City and Zhangjiagang County of Suzhou City in southern Jiangsu Province, Hai’an County of Nantong City and Yandu District of Yancheng City in Central Jiangsu Province, and Suining County of Xuzhou City and Sihong County of Suqian City in northern Jiangsu Province during the period between May and October, 2020. A small ponding container was sampled, and larval Aedes mosquitoes were collected using straws once each in early and late stages of each month. All larvae were bred in laboratory to adults for population identification. In addition, larval breeding were observed in all small ponding containers in and out of 30 households that were randomly sampled from six surveillance sites, and the larval mosquito density was estimated using Breteau index. Larval A. albopictus mosquitoes were sampled around Cuiyuan New Village in Jintan District of Changzhou City, and bred in laboratory to the first offspring generation, and the susceptibility of adult female mosquitoes to deltamethrin, lambda-cyhalothrin, malathion, and propoxur was tested using the filter-paper bioassay recommended by WHO. Results A total of 1 165 larval Aedes mosquitoes were captured from small ponding containers in six surveillance sites of Jiangsu Province in 2020, and all were identified as A. albopictus following eclosion. The largest number of Aedes larvae captured was found in July. A total of 1 152 households were investigated in six surveillance sites, and the mean Breteau indexes were 9.58, 13.20, 13.71, 13.20, 12.18 and 5.58 from May to October, respectively, while a high Aedes transmission risk was seen in Xinbei District of Changzhou City, with a higher Breteau index than in Suining (H = 23.667, Padjusted = 0.001) and Sihong (H = 22.500, Padjusted = 0.003) counties. The field-captured A. albopictus from Cuiyuan New Village in Jintan District of Changzhou City remained sensitive to malathion, but was resistant to propoxur, and developed high-level resistance to deltamethrin and lambda-cyhalothrin. Conclusions A. albopictus was present in southern, central and northern Jiangsu Province in 2020, and the larval density peaked in July. A. albopictus captured from Cuiyuan New Village in Jintan District of Changzhou City has developed high-level resistance to pyrethroid pesticides.

Mosquito larva distribution and natural Wolbachia infection in campus areas of Nakhon Ratchasima, Thailand

Objective: To determine the prevalence of mosquito larvae in campus areas and the infection rate of endosymbiotic bacteria, Wolbachia in mosquito larvae. Method: The mosquito larvae samples were collected in residential areas and academic buildings of Suranaree University of Technology located in Northeastern Thailand during 2017-2018. Mosquito species identification was performed using GLOBE mosquito protocols and Rattanarithikul & Panthusiri's keys. The gene encoding for the surface protein of Wolbachia was amplified by PCR and confirmed by DNA sequencing. Results: Armigeres sp. is the highest proportion of mosquito larvae followed by Culex spp., Aedes albopictus, Aedes aegypti, and Toxorynchites spp., respectively. Aedes aegypti have breeding sites mostly in the containers found indoors, whereas the main breeding sites of Aedes albopictus were found in both outdoors and indoors. The House Index and Breteau Index for Aedes spp. was more than 5% and 20%, respectively, in both areas, indicating that these areas are dengue sensitive. The highest proportion of Wolbachia infection was found in the larvae of Culex spp. (86.21%), followed by Aedes albopictus (69.23%) and rarely detected in Aedes aegypti (9.09%). Conclusion: The present study reported the first natural infection of Wolbachia in mosquito larvae in Thailand. Our result suggested that the mosquito species containing higher proportion of Wolbachia are less likely to be vectors for dengue. Therefore, Wolbachia transfection in mosquito larvae could be applied as a biocontrol for dengue and other mosquito-borne disease prevention.

Mosquito density in rural Kerala: a study on the trend of Aedes larval indices over monsoon in a rural area of Thrissur district, India

Background: Dengue is one of the most rapidly spreading mosquito-borne viral diseases in the world. Aedes aegypti mosquito is the main vector of dengue and Chikungunya. Entomological surveillance on Aedes mosquito has been standardized on different indices like House index, Container index, Breteau index. Larval indices are important predictors of outbreaks and are valuable in taking preventive measures. The objectives of the present study was to study the trend of larval indices over four months in selected wards of Kaiparambu Panchayat, Thrissur, Kerala, India and to identify the major breeding sources.Methods: A series of surveys were conducted from May to August of 2017 in Kaiparambu Panchayat under the field practice area of Amala Institute of Medical Sciences Thrissur. Houses were selected serially from 4, 5 and 6 wards with roughly 120 houses being covered each month.Results: A total of 489 houses were surveyed over 4 months. Overall, positive containers (with larvae) were present in 375 of 4055 potential containers showing a calculated House index (HI) is 44.4%, Container index (CI) is 11.5% and the Breteau Index is 76.7%. All three indices increased from May to June, peaked in July and dropped by August. Plastic containers were the most common source of breeding.Conclusions: The indices indicate risk even in the pre-monsoon season and there is a marked rise during monsoon. Hence, control measures need to be adopted during the pre-monsoon season so as to reduce the impact of the impending outbreak.

A study on mosquito density in rural Kerala before and after floods

Background: Mosquito borne diseases are a major public health problem in Kerala. Mosquito density assessed by larval surveys is easier and quicker to perform. The larval indices are an important practical predictor of outbreaks of mosquito borne disease and are valuable in taking preventive measures. This study is done to calculate standardized larval indices namely house index, container index and Breteau index and to identify the major breeding sources of mosquitoes in the residential environment in a rural of Thrissur, Kerala.Methods: A cross-sectional study selecting 80 houses from 1 wards of Konnikara village under Thrikkur Panchayath under the field practice area of rural training centre, Amala Institute of Medical Sciences Thrissur. Every water holding container indoors and outdoors was counted and searched for larval presence and noted on a pretested format.Results: In this study, 80 houses were surveyed in 2 days initially in June and in September. All the entomological indices were found to be above the critical level in the initial survey in June. House index=36% container index=44%; Breteau index=143% showing high chances for outbreaks of mosquito borne diseases. In September though the indices were very low house index 1.25% container index 2.77% and Breteau index.Conclusions: The area is prone for mosquito borne disease outbreaks like dengue fever and after interventions the vector indices and potential risks came down

Definition of dengue risk thresholds of route index and mosq-ovitrap index / 预防医学

Objective @#To estimate the risk threshold of route index（RI）and mosq-ovitrap index（MOI）based on Breteau index（BI）,as supplements for dengue fever risk monitoring in specific habitats. @*Methods @#Two towns and two streets were selected from nine towns（streets）in Jiashan County,and then one village（community）was selected from each of them as a Aedes albopictus monitoring site. The BI,RI and MOI were employed at the same time and area from April to October in the year 2018. Linear regression models were built with RI,MOI and BI to calculate the dengue risk threshold of RI and MOI according to BI. @*Results @#The linear regression model of BI（X）and RI（Y）was Y=0.145+0.662X（P<0.05）,of BI（X）and MOI（Y）was Y=3.423+0.524X（P<0.05）. If BI=5（having risk of transmission of dengue fever）,then RI=3.455（95%CI：1.717-5.198）,MOI=6.043（95%CI：-0.327-12.417）. If BI=10（having risk of outbreak）,then RI=6.765（95%CI：5.018-8.518）,MOI=8.663（95%CI：2.260-15.071）. If BI=20（having risk of epidemic）,then RI=13.385（95%CI：11.326-15.453）,MOI=13.903（95%CI：6.352-21.461）.@*Conclusion @#The dengue fever risk threshold of RI estimated by BI had a narrow 95%CI and could be applied for dengue fever risk assessment,while the risk threshold of MOI had a wide 95%CI and the application value needed further study.

Measuring Aedes & Breteau Indices in Determining Dengue Outbreak; A Study in Kota Tinggi

@#Introduction Dengue fever, the most known vector-borne disease in the tropical and subtropical regions has become major public health concern worldwide. Rapid urbanization, increased population movement and poor public hygienic lifestyle contributed to the proliferated of high incidence of dengue fever in urban and semi urban areas. With the increasing trend of dengue cases and deaths, methods of dengue surveillance should be reevaluated in predicting dengue outbreak. Methods This study aimed to determine association between Aedes Index and Breteau Index with dengue outbreak in the district of Kota Tinggi, Johor. Results Total of 593 dengue cases in 2015 collected from Kota Tinggi Health Office. The study found that there were significant association between Aedes Index and Breteau Index with localities (p< 0.01) significant association between dengue outbreak incidence and low transmission of aedes indices (p<0.01). However these indices reported low sensitivity and specificity in predicting dengue outbreak in this area. Conclusions As dengue disease remains a major endemic in Malaysia, better surveillance index should be reconsider as the main surveillance for dengue disease.

The Impacts of Mosquito Density and Meteorological Factors on Dengue Fever Epidemics in Guangzhou, China, 2006-2014: a Time-series Analysis / 生物医学与环境科学（英文）

<p><b>OBJECTIVE</b>To explore the associations between the monthly number of dengue fever(DF) cases and possible risk factors in Guangzhou, a subtropical city of China.</p><p><b>METHODS</b>The monthly number of DF cases, Breteau Index (BI), and meteorological measures during 2006-2014 recorded in Guangzhou, China, were assessed. A negative binomial regression model was used to evaluate the relationships between BI, meteorological factors, and the monthly number of DF cases.</p><p><b>RESULTS</b>A total of 39,697 DF cases were detected in Guangzhou during the study period. DF incidence presented an obvious seasonal pattern, with most cases occurring from June to November. The current month's BI, average temperature (Tave), previous month's minimum temperature (Tmin), and Tave were positively associated with DF incidence. A threshold of 18.25 °C was found in the relationship between the current month's Tmin and DF incidence.</p><p><b>CONCLUSION</b>Mosquito density, Tave, and Tmin play a critical role in DF transmission in Guangzhou. These findings could be useful in the development of a DF early warning system and assist in effective control and prevention strategies in the DF epidemic.</p>

Clinico-Epidemiological Profile of an Outbreak of Dengue Fever in Rural Area of Ambajogai Mandai, District Beed.

A c1inico-epidemiological study of fever cases was carried out in three villages of Ambajogai Mandal, Beed, Maharashtra. Out of 123 fever cases studied, most common affected age group was 21-45 years with more number of females i.e.55.28%. The patients mainly presented with fever and joint pain with no any evidence of haemorrhagic manifestation. Of the 36 blood samples tested 03 samples were found positive for IgM antibodies to dengue virus. Larval survey showed highest breeding preference in domestic water container like earthen pots. Entomological indices were found out to be higher as house index 19.76%; container index 19.02%; Breteau index 22.31%. Clinico-epidemiological, laboratory and entomological investigations indicate present episode of fever outbreak was due to dengue fever. It demands for strengthening the surveillance activity and alert reporting of peripheral health staff along with IEC activities for community participation and involvement of other departments.