Prevention of malaria with pyrethroid treated bednets

Malaria parasites (Plasmodium) are carried from person to person by female mosquitoes of the genus Anopheles. 80-90% of malaria incidence worldwide occurs in Africa. The main Anopheles species in Africa which bite humans are A. gambiae and A. funestus. Since these animals feed upon humans mainly during late night when most people are in bed, the consistent use of bednets can block the transmission of malaria. However, bednets should be treated with synthetic pyrethroid insecticides, for the physical barrier of bednets is often inadequate to prevent the entry of Anopheles. In addition, the mosquitoes are drawn to the bednets by the carbon dioxide and body odor emitted by the occupant. The insecticide-treated nets therefore double as mosquito traps. Bednets are treated by dipping them into an aqueous emulsion of a pyrethroid, wringing them out, then laying them out to dry. A considerable number of mosquitoes can be killed with a relatively small amount of insecticide. A treated net's insecticidal power can be tested by wrapping part of it around a wire frame, then introducing some Anopheles mosquitoes inside the frame. A median mosquito knockdown time of less than 10 minutes inside the net indicates a good pyrethroid deposit. The persistence of a net's insecticidal power is considerably reduced if the net is vigorously washed. People vary in the frequency they wash their nets. Most villagers in Tanzania were found to wash and retreat their nets every 6 months.     

哈尔滨市售蔬菜中有机磷和拟除虫菊酯农药的残留量

目的了解哈尔滨市蔬菜中有机磷农药、拟除虫菊酯类农药的残留情况,为政府相关部门制订政策提供依据。方法于2007年5—10月,从哈尔滨市10个主要农贸市场和5个超市采集大辣椒、小辣椒、黄瓜、西红柿、豆角、菠菜、油菜、大头菜、花菜和白菜菜样各15件,采用气相色谱法检测其农药的残留情况。结果共检测出4种有机磷农药(甲胺磷:0.003 1～0.048 8mg/kg;敌敌畏:0.001 5～0.052 7mg/kg;氧化乐果:0.003 9～0.3449mg/kg;水胺硫磷:0.0026～0.0869mg/kg)和3种拟除虫菊酯类农药(氯氰菊酯:0.018 1～0.324 5 m/kg;氰戊菊酯:0.024 7～0.024 8 mg/kg;溴氰菊酯:0.039 4～0.044 1 mg/kg)残留,甲拌磷、乐果、甲基对硫磷均未检出残留。农药残留超标率由高至低依次为氧化乐果(24.00%)>甲胺磷(20.67%)>水胺硫磷(4.67%)。氧化乐果在10种蔬菜中均有检出,氯氰菊酯在9种蔬菜中检出,敌敌畏和甲胺磷分别在7种蔬菜中检出。结论本次调查的蔬菜中普遍存在有机磷、拟除虫菊酯类农药的残留。     

The attribution of urban and suburban children's exposure to synthetic pyrethroid insecticides: a longitudinal assessment

Despite the widespread use of synthetic pyrethroid insecticides that led to common exposure in the population, very few studies have been conducted to quantitatively assess human, particularly, children's, long-term exposures to pyrethroid insecticides. The objective of the Children Pesticide Exposure Study - Washington (CPES-WA) was to establish the longitudinal exposure profiles for pyrethroid insecticides in a cohort of children living in an urban and suburban community using urinary pyrethroid metabolites as exposure biomarkers. The results from this analysis will allow us to examine potential risk factors in relation to the elevated pyrethroid insecticide exposure in children. A total of 23 children, aged 3-11 years, who only consumed conventional diets were enrolled in this 1-year study. We provided organic food items to children for 5 consecutive days in the summer and fall sampling seasons. We measured urinary metabolites for the synthetic pyrethroid insecticides in urine samples that were collected twice daily during each of the four sampling seasons. 3-phenoxybenzoic acid was frequently detected in the urine samples with mean and median daily volume-weighted average levels of 1.5 and 1.2 microg/l, followed by trans-2,2-(dichloro)-2-dimethylvinylcyclopropane carboxylic acid (1.4 and 1.0 microg/l) and cis-2,2-(dichloro)-2-dimethylvinylcyclopropane carboxylic acid (0.5 microg/l, and non-detected). When we took into account season, age, sex, diet, and self-reported residential use of pyrethroid insecticides in a linear mixed-effects model, the results suggested that the combination of the use of pyrethroid insecticides in the household, dietary intake, and seasonal differences play a significant role in predicting children's exposure to synthetic pyrethroid insecticides. We found CPES-WA children were continuously exposed to pyrethroid insecticides through their diets all year long, and this chronic exposure pattern was periodically modified by episodes of relatively high exposures from residential uses. Future research should be devoted to enhancing our understanding of the complexity of pyrethroid insecticide exposure patterns.     

Evaluation of a polymerase chain reaction assay for detection of pyrethroid insecticide resistance in the malaria vector species of the Anopheles gambiae complex

A published polymerase chain reaction assay proved reliable for detecting nerve-insensitivity (kdr-type) resistant and susceptible alleles to the pyrethroid insecticide permethrin in the malaria vectors Anopheles gambiae s.s. and An. arabiensis and the nonvector species An. quadriannulatus. The assay detects pyrethroid susceptible and resistance alleles mediated by a mutation in region II of the para-type sodium channel gene, showing that resistance is conferred by pyrethroid target site insensitivity. Analysis of results of the assay suggests that more than 1 mechanism conferring pyrethroid resistance is operating in an An. gambiae s.s. strain from C?te d'Ivoire. The value of the assay as a tool for monitoring this mode of insecticide resistance in wild populations is discussed.     

2006年陕西省六地市蔬菜水果农药残留状况

目的了解2006年陕西省蔬菜水果中有机磷农药、三氯杀螨醇、氨基甲酸酯、拟除虫菊酯类农药的残留水平。方法采用随机与定点抽样的方法采集市售蔬菜水果16个品种共265份样品，通过气相色谱法和高效液相色谱法进行定性和定量分析。结果有机磷总检出率5．97％，超标率4．65％；三氯杀螨醇检出率30．19％，超标率30．19％；氨基甲酸酯检出率2．74％，超标率0．09％；拟除虫菊酯检出率5．81％，超标率2．94％。结论该省有部分蔬菜水果有农药残留，并检出国家禁用的农药品种，三氯杀螨醇和个别拟除虫菊酯检出率较高，应加强强农药使用的监管，保证农产品安全。     

The Gambian National Impregnated Bednet Programme: Evaluation of the 1994 cost recovery trial

Following the success of a controlled trial of insecticide-impregnated bednets in reducing mortality in children. The Gambia started a National Impregnated Bednet Programme (NIBP) in 1992. The objectives of this programme were to introduce impregnated bednets into all primary health care (PHC) villages and to establish a system of cost recovery over a three-year period. During the initial phase of the programme, when insecticide was given out free, a high uptake was achieved. However, after small user charges were introduced in 1993, coverage dropped to a low level. In 1994, different systems of insecticide distribution and permethrin formulations were tried in an attempt to improve coverage. A nationwide cross-sectional survey carried out during the 1994 rainy season measured coverage by distribution channel, as well as the knowledge, attitudes and practices of health workers and villagers during the intervention. Overall, only 16% of bednets were impregnated in 1994, compared to 80% when the insecticide was offered free of charge in previous years. Lack of money was the major reason given by villagers for not impregnating their bednets in 1994. Use of impregnated bednets was higher in areas where the sale of permethrin emulsion by village health workers was supplemented by the sale of insecticide in individual packages through shops. In villages where insecticide was distributed free to women with small children through governmental mother and child health (MCH) services, higher levels of coverage were achieved among women and young children than in villages where other distribution systems were used. We conclude that the sale of insecticide through the private sector may increase bednet impregnation rates in African communities, and that the free distribution of insecticide through MCH services may be an effective way of targeting young children, the group most at risk of malaria.     

Insecticide susceptibility in Anopheles pseudopunctipennis from Colombia: comparison between bioassays and biochemical assays

Anopheles pseudopunctipennis, one of the primary vectors of malaria in the southwest of Colombia, was evaluated for susceptibility to the 3 major insecticide groups (organophosphates, pyrethroids, and carbamates) by bioassay and biochemical assay. Larval populations, which were collected principally from irrigation channels in agricultural areas, where the intensity of insecticide use varied, were utilized to establish susceptibility for the 1st time in this species. The baselines for each population showed a range of biological susceptibility to the insecticides evaluated, but overall no resistance was detected according to standards established by the World Health Organization. The high sensitivity of biochemical microassays enabled the detection of a small proportion of mosquitoes with higher levels of nonspecific esterases and mixed-function oxidases from 2 areas where agricultural application of organophosphate and pyrethroid insecticides had been heavy. These differences were not sufficient to affect susceptibility as measured by bioassay. No evidence of insensitive acetylcholinesterase was observed. Absence of resistance in areas that have experienced heavy insecticide application could be explained by genetic drift, by gene flow from areas without insecticide pressure, by manner of exposure to the insecticides, or by recent changes in agricultural activities that decreased insecticide use. Baseline values were established that serve as provisional susceptibility thresholds for applying simple Centers for Disease Control and Prevention biochemical assay and bioassay methods to larvae of this anopheline species.     

Fluctuating asymmetry and exposure to pyrethroid insecticides in Triatoma infestans populations in northeastern Argentina

Fluctuating asymmetry (FA), a phenotypic marker used as indicator of developmental stress or instability, is sometimes associated with insecticide application and resistance. Here we investigated the occurrence and amount of wing size and wing shape FA in Triatoma infestans females and males collected before and 4 months after a community-wide pyrethroid spraying campaign in a well-defined rural area of Pampa del Indio, Argentina. Moderate levels of pyrethroid resistance were previously confirmed for this area, and postspraying house infestation was mainly attributed to this condition. In the absence of insecticide-based selective pressures over the previous 12 years, we hypothesized that 1- if postspraying triatomines were mostly survivors to insecticide spraying (pyrethroid resistant), they would have higher levels of FA than prespraying triatomines. 2- if postspraying triatomines have a selective advantage, they would have lower FA levels than their prespraying counterparts, whereas if postspraying infestation was positively associated with immigrants not exposed to the insecticide, prespraying and postspraying triatomines would display similar FA levels. For 243 adult T. infestans collected at identified sites before insecticide spraying and 112 collected 4 months postspraying, wing size and wing shape asymmetry was estimated from landmark configurations of left and right sides of each individual. At population level, wing size and shape FA significantly decreased in both females and males after spraying. Males displayed greater wing size and shape FA than females. However, at a single peridomestic site that was persistently infested after spraying, FA declined similarly in females whereas the reverse pattern occurred in males. Our results suggest differential survival of adults with more symmetric wings. This pattern may be related to a selective advantage of survivors to insecticide spraying, which may be mediated or not by their pyrethroid-resistant status or to lower triatomine densities after insecticide spraying and the concomitant increase in feeding success.     

Assessing Children’s Dietary Pesticide Exposure: Direct Measurement of Pesticide Residues in 24-Hr Duplicate Food Samples

Background

The data presented here are a response to calls for more direct measurements of pesticide residues in foods consumed by children and provide an opportunity to compare direct measures of pesticide residues in foods representing actual consumption with those reported by the U.S. Department of Agriculture Pesticide Data Program.

Objective

We measured pesticide residues in 24-hr duplicate food samples collected from a group of 46 young children participating in the Children’s Pesticide Exposure Study (CPES).

Methods

Parents were instructed to collect 24-hr duplicate food samples of all conventional fruits, vegetables, and fruit juices equal to the quantity consumed by their children, similarly prewashed/prepared, and from the same source or batch. Individual or composite food items were analyzed for organophosphate (OP) and pyrethroid insecticide residues.

Results

We collected a total of 239 24-hr duplicate food samples collected from the 46 CPES children. We found 14% or 5% of those food samples contained at least one OP or pyrethroid insecticide, respectively. We measured a total of 11 OP insecticides, at levels ranging from 1 to 387 ng/g, and three pyrethroid insecticides, at levels ranging from 2 to 1,133 ng/g, in children’s food samples. We found that many of the food items consumed by the CPES children were also on the list of the most contaminated food commodities reported by the Environmental Working Group.

Conclusions

The frequent consumption of food commodities with episodic presence of pesticide residues that are suspected to cause developmental and neurological effects in young children supports the need for further mitigation.     

Characterisation of DDT, pyrethroid and carbamate resistance in Anopheles funestus from Obuasi, Ghana

Indoor-resting anopheline mosquitoes were collected from Obuasi, Ghana, and were identified morphologically and by PCR as Anopheles funestus Giles. Wild-caught females were induced to lay eggs. Samples of F1 progeny from each family were divided into cohorts and were either exposed to DDT and permethrin or were stored for biochemical analysis. Bioassay data by family show evidence of DDT and pyrethroid resistance in the parent A. funestus population. The sodium channel gene of DDT survivors and DDT-susceptible individuals was PCR amplified and sequenced to determine whether any kdr-type mutations were present. Molecular analysis of the IIS5-IIS6 segment of the sodium channel gene gave no indication of any kdr-type mutations associated with resistance phenotypes. Biochemical analysis suggests that DDT and pyrethroid resistance may be metabolically mediated, although there were no clear correlations between enzyme levels/activities and insecticide resistance across families. Furthermore, an altered acetylcholinesterase conferring carbamate resistance was evident. These results can be used to plan an effective malaria control strategy in the Obuasi region.     

Pyrethroid pesticides and their metabolites in vacuum cleaner dust collected from homes and day-care centers

Urinary metabolites of pyrethroid pesticides have been used as biomarkers to estimate human exposure to the parent insecticide. It is important to establish whether these markers are present in environments or media to which humans are exposed routinely. Failure to account for the contribution of pre-existing markers to urinary concentrations could result in risk assessments that overestimate exposure. The purpose of this study was to quantify the concentrations of 13 selected pyrethroid pesticides and their degradation products in samples of indoor dust that had been collected in vacuum cleaner bags during the children's total exposure to persistent pesticides and other persistent organic pollutants (CTEPP) study of homes and day cares in North Carolina and Ohio. Sieved contents of 85 vacuum cleaner bags were analyzed, and permethrin was found in all samples. Sixty-nine samples contained at least one additional pyrethroid, but none contained more than five pyrethroids in detectable concentrations. Resmethrin, prallethrin, and fenpropathrin were not detected in any samples, while 36 contained phenothrin. The median concentration of permethrin in the samples was 1454 ng/g of dust. Excluding permethrin, pyrethroid concentrations were typically less than or equal to 100 ng/g of dust. The majority of degradates were present in more than half of the dust samples, usually at concentrations of less than or equal to 100 ng/g of dust. For those pyrethroids with a characteristic oxydibenzene group, the cyclopropane degradates were present at higher concentrations than the corresponding benzoic acid moieties. Using urinary concentrations of these metabolites to model human exposure to the parent pyrethroids, may over-estimate risk due to the presence of pre-existing degradates in dust.     

Current and Historically Used Pesticides in Residential Soil from 11 Homes in Atlanta, Georgia, USA

We used a multiresidue, gas chromatography/mass spectrometry-based method to measure seven pyrethroid, five organophosphorus (OP), and six organochlorine pesticides in soil collected from 11 Atlanta homes in 2006. Our objective was to collect preliminary data for a larger study of pesticide exposures among Atlanta children. The pyrethroid insecticides (cis- and trans-permethrin, bioallethrin) were the most commonly detected analytes, giving evidence of widespread outdoor use among our study homes. Our pyrethroid insecticide detection frequencies were higher than those reported in a recent study of Ohio and North Carolina homes; however, our maximum values were approximately half of those reported. We detected the target OP pesticides in only a few samples, but we found two restricted-use OP pesticides—methyl parathion and terbufos—and thus possible evidence of illegal residential use or environmental persistence in soil. We also detected dichlorodiphenyltrichloroethane (DDT) and dichlorodiphenyldichloroethane (DDE) in samples from six homes. Although our small sample size limits comparison to other studies, our results provide evidence that residential soil is a potential source of human exposure to both current and historically used pesticides.     

江西省市售茶叶中9,10-蒽醌的污染调查分析

目的 了解江西省市售茶叶中9,10-蒽醌污染状况,初步探究蒽醌污染来源。方法 从江西省11个地市采集4类茶叶样品共112份,样品中的9,10-蒽醌经有机溶剂提取,凝胶色谱净化,气相色谱串联质谱仪进行测定,同位素内标法定量。结果 112份茶叶中9,10-蒽醌检出率为100%,检出范围为0.004~0.081mg/kg,平均含量为0.023mg/kg。根据欧盟法规条例（EU）No 1146/2014对茶叶蒽醌限量0.02mg/kg判定,4类茶叶共超标44份,总超标率为39.3%。其中红茶超标率最低为27.3%,绿茶和青茶超标率分别为35.0%和38.5%,黑茶超标率最高为78.6%。不同包装类型中,定型包装和散装超标率分别为52.2%和30.3%。不同采样环节中,商店和农贸市场采样超标率分别为38.8%和34.4%。结论 江西省市售的4类茶叶中9,10-蒽醌污染较为严重,尤其以定型包装的黑茶污染水平最高,初步分析茶叶的制作工艺和包装材料可能是蒽醌的主要污染来源,提醒企业采取有效措施控制污染来源,建议政府部门加大对茶叶中蒽醌的监测力度,制定蒽醌限量标准以保障百姓的饮食安全。     

液质联机测定尿中拟除虫菊酯类农药代谢物的方法研究

[目的]建立用液相色谱-质谱法测定人尿中3种拟除虫菊酯类农药代谢物(3-PBA、Cis-Cl2CA和Trans-Cl2CA)的定量方法。[方法]样品经酸水解、液液萃取后,用Zorbax SB C18柱分离、大气压化学电离源检测、内标法定量。[结果]方法线性良好,相关系数(R2)>0.998,3个代谢物的日内、日间回收率范围在90.0%～110.0%之间,相对标准偏差(RSD)小于10.0%,检出限为0.20μg/L。[结论]该方法简单、方便、成本低,能满足从普通人群到职业特殊人群的生物监测工作的要求。     

An intervention to reduce residential insecticide exposure during pregnancy among an inner-city cohort

BACKGROUND: We previously reported widespread insecticide exposure during pregnancy among inner-city women from New York City. Here we report on a pilot intervention using integrated pest management (IPM) to reduce pest infestations and residential insecticide exposures among pregnant New York City African-American and Latina women (25 intervention and 27 control homes). METHODS: The IPM consisted of professional cleaning, sealing of pest entry points, application of low-toxicity pesticides, and education. Cockroach infestation levels and 2-week integrated indoor air samples were collected at baseline and one month postintervention. The insecticides detected in the indoor air samples were also measured in maternal and umbilical cord blood collected at delivery. RESULTS: Cockroach infestations decreased significantly (p = 0.016) after the intervention among intervention cases but not control households. Among the intervention group, levels of piperonyl butoxide (a pyrethroid synergist) were significantly lower in indoor air samples after the intervention (p = 0.016). Insecticides were detected in maternal blood samples collected at delivery from controls but not from the intervention group. The difference was significant for trans-permethrin (p = 0.008) and of borderline significance (p = 0.1) for cis-permethrin and 2-isopropoxyphenol (a propoxur metabolite). CONCLUSION: To our knowledge, this is the first study to use biologic dosimeters of prenatal pesticide exposure for assessing effectiveness of IPM. These pilot data suggest that IPM is an effective strategy for reducing pest infestation levels and the internal dose of insecticides during pregnancy.     

Dissipation of Chlorantraniliprole in Tomato Fruits and Soil

The main objective of this study was to understand the residue and persistence behaviour of new insecticide chlorantraniliprole in tomato fruit and soil samples. Its residue was analyzed by HPLC and it dissipated in tomato fruit and soil following first order kinetics. The results showed half life (t_1/2) value of 3.30 and 3.66 days for chlorantraniliprole in tomato fruit and soil, respectively. According to maximum residue limit (MRL) the pre-harvest interval (PHI) of chlorantraniliprole on tomato was 8-days after the treatment.     

Insecticide treated bednet strategy in rural settings: can we exploit women's decision making power?

Use of insecticide treated bednets in prevention of malaria is a widely propagated global strategy, however, its use has been reported to be influenced and limited by many variables especially gender bias. A cross sectional field epidemiological study was conducted in a rural setting with two outcome variables, 'Bednet use'(primary outcome variable) and 'Women's Decision Making Power' which were studied in reference to various predictor variables. Analysis reveals a significant effect on the primary outcome variable 'Bednet use' of the predictor variables- age, occupation, bednet purchase decision, women's decision making power, husband's education and knowledge about malaria and its prevention. The study recommends IEC on treated bednets to be disseminated through TV targeting the elderly women who have better decision making power and mobilizing younger women who were found to prefer bednets for prevention of mosquito bites for optimizing the use of treated bednets in similar settings.     

A cost analysis of the employer-based bednet programme in Coastal and Western Kenya

Malaria remains a major health problem in Africa. One preventative strategy currently advocated is the use of bednets, preferably treated with insecticide. Many approaches to bednet delivery have been adopted in Kenya, including an employer-based malaria control strategy (EBMC). The cost and sustainability of this approach have not previously been assessed. This paper presents the financial cost (cash expenditure) of the EBMC programme implemented in the Coastal and Western regions of Kenya by the African Medical and Research Foundation (AMREF) between April 1998 and February 2002. Getting a bednet and insecticide to an employee was estimated to cost the provider US$15.8. This could be reduced by US$0.5 if the remaining stocks were liquidated and by an additional US$1.3 if the salvage of capital items is considered. The venture of distributing bednets to employees through the programme proved lucrative to organized community groups (OCGs), for they made between 24 and 29% gross profit from the nets they sold. Consequently, OCGs in nine of the 13 companies involved had retained enough funds from which they could buy and sell bednets without further donor financial support, and this portrays some elements of a sustainable supply system.     

浙江省不同地区淡色库蚊杀虫剂抗药性监测

目的对浙江省不同地区淡色库蚊抗药性水平进行调查,了解淡色库蚊的抗性表型与有关基因特征及其相关性,为浙江省蚊虫控制提供科学依据。方法淡色库蚊抗药性表型采用幼虫浸渍法;对浙江省4个区域的淡色库蚊进行抗药性测定,基因型研究采用PCR扩增后测序确定。结果不同地区淡色库蚊抗药性表型差异较大,对高效氯氰菊酯、溴氰菊酯、丙烯菊酯、敌敌畏、三氯杀虫酯、残杀威的半数致死浓度（LC50）分别在同类药物抗性差异变化范围为2．1～42．8倍,其中以高效氯氰菊酯抗性差异最高。舟山种群拟除虫菊酯类药物抗性水平明显高于其他地区,其拟除虫菊酯抗性相关基因YSSC基因具有较高多态性,部分样本V3$C基因内含子区域出现3个紧邻的大小分别为20、53和40bp的片段缺失。结论浙江省不同地区淡色库蚊抗性表型差异较大,抗性基因监测发现舟山种群kdr基因存在较复杂的多态性,是否为导致其抗性表型变化的直接原因还有待进一步研究证实。     

国际航行船舶携带德国小蠊抗药性调查

目的了解国际航行船舶携带的德国小蠊抗药性情况,为口岸防治合理用药提供科学依据。方法采集国际航行船舶上孳生的德国小蠊自然种群,带回实验室繁育,培养1代后,取2～3周龄雄性成虫,用药膜接触法测定其对丙烯菊酯、溴氰菊酯、敌敌畏、仲丁威、残杀威、毒死蜱、高效氯氰菊酯7种杀虫剂的抗性倍数。结果采自3艘国际航行船舶的德国小蠊对7种杀虫剂的抗性依次为2.54～5.56、2.18～5.14、3.98～5.87、1.57～1.91、0.83～1.27、1.06～1.59、2.89～3.93倍。结论 3艘国际航行船舶携带的德国小蠊对菊酯类及有机磷类杀虫剂敌敌畏已产生耐药性或抗药性,对氨基甲酸酯类杀虫剂及毒死蜱较为敏感,口岸防治德国小蠊可采用氨基甲酸酯类杀虫剂。