Insecticide resistance in head lice: clinical,parasitological and genetic aspects

Insecticide treatment resistance is considered to be a major factor in the increasing number of infestations by head lice. The large insecticide selection pressure induced by conventional topical pediculicides has led to the emergence and spread of resistance in many parts of the world. Possible mechanisms of resistance include accelerated detoxification of insecticides by enzyme-mediated reduction, esterification, oxidation that may be overcome by synergistic agents such as piperonyl butoxide, alteration of the binding site, e.g. altered acetylcholinesterase or altered nerve voltage-gated sodium channel, and knockdown resistance (kdr). Clinical, parasitological and molecular data on resistance to conventional topical pediculicides show that treatments with neurotoxic insecticides have suffered considerable loss of activity worldwide. In particular, resistance to synthetic pyrethroids has become prominent, probably because of their extensive use. As other treatment options, including non-insecticidal pediculicides such as dimeticone, are now available, the use of older insecticides, such as lindane and carbaryl, should be minimized, owing to their loss of efficacy and safety concerns. The organophosphorus insecticide malathion remains effective, except in the UK, mostly in formulations that include terpineol.     

The spread of the Leu-Phe kdr mutation through Anopheles gambiae complex in Burkina Faso: genetic introgression and de novo phenomena

During extensive sampling in Burkina Faso and other African countries, the Leu-Phe mutation producing the kdr pyrethroid resistance phenotype was reported in both Anopheles gambiae ss and A. arabiensis. This mutation was widely distributed at high frequency in the molecular S form of A. gambiae while it has been observed at a very low frequency in both the molecular M form and A. arabiensis in Burkina Faso. While the mutation in the M form is inherited through an introgression from the S form, its occurrence is a new and independent mutation event in A. arabiensis. Three nucleotides in the upstream intron of the kdr mutation differentiated A. arabiensis from A. gambiae ss and these specific nucleotides were associated with kdr mutation in A. arabiensis. Ecological divergences which facilitated the spread of the kdr mutation within the complex of A. gambiae ss in West Africa, are discussed.     

Malaria control by residual insecticide spraying in Chingola and Chililabombwe,Copperbelt Province,Zambia

Malaria is endemic in the whole of Zambia and is the leading cause of morbidity and mortality. Prior to 1980, effective malaria control was achieved in the northern mining towns of Chingola and Chililabombwe by means of annual residual spraying programmes. In the 1970s, incidence rates were as low as 20/1000 p.a., but by 2000 had increased to 68/1000 p.a. in Chingola and to 158/1000 p.a.in Chililabombwe. Konkola Copper Mines (KCM) initiated a malaria control programme in which all dwellings in the two towns and within a 10-km radius were sprayed with either dichlorodiphenyltrichloroethane or a synthetic pyrethroid (Icon by ZENECA or Deltamethrin by Aventis). Houses were sprayed in November and December 2000, at the start of the peak transmission period. There was a statistically significant reduction in malaria incidence recorded at KCM health facilities in the two towns, representing a protective incidence rate ratio of 0.65 (95% CI 0.44, 0.97) when comparing the post-spraying period with the corresponding period of the previous 2 years. This reduction followed a single round of house spraying during a year with higher rainfall than the preceding two and in an area where chloroquine was first-line treatment. This house-spraying programme is an example of private/public sector collaboration in malaria control.     

Selenium modulates β‐cyfluthrin‐induced liver oxidative toxicity in rats

This study was designed to investigate the possibility of β‐cyfluthrin to induce oxidative stress and biochemical perturbations in rat liver and the role of selenium in alleviating its toxic effects. Male Wister rats were randomly divided into four groups of seven each, group I served as control, group II treated with selenium (200 µg/kg BW), group III received β‐cyfluthrin (15 mg/kg BW, 1/25 LD₅₀), and group IV treated with β‐cyfluthrin plus selenium. Rats were orally administered their respective doses daily for 30 days. The administration of β‐cyfluthrin caused elevation in lipid peroxidation (LPO) and reduction in the activities of antioxidant enzymes including catalase (CAT), superoxide dismutase (SOD), glutathione S‐transferase (GST), glutathione peroxidase (GPx), and glutathione reductase (GR). A decrease in reduced glutathione (GSH) content was also observed. Liver aminotransferases (AST and ALT) and alkaline phosphatase (ALP) were decreased, whereas lactate dehydrogenase (LDH) was increased. Selenium in β‐cyfluthrin‐induced liver oxidative injury of the rats modulated LPO, CAT, SOD, GSH, GST, GPx, and GR. Also, liver AST, ALT, ALP, and LDH were maintained near normal level due to selenium treatment. It is concluded that selenium scavenges reactive oxygen species and render a protective effect against β‐cyfluthrin toxicity. © 2013 Wiley Periodicals, Inc. Environ Toxicol 29: 1323–1329, 2014.     

急性拟除虫菊酯中毒的临床表现及诊断

国外迄今尚未见有急性拟除虫菊酯中毒的临床报告。国内医学文献自1982年至1988年则已报道急性拟除虫菊酯中毒共573例,其中生产性中毒229例,意外性中毒344例。以急性溴氰菊酯中毒最为多见(325例),其次为戊氰菊酯(196例)及氯氰菊酯(45例)等急性中毒。本文对573例急性拟除虫菊酯中毒的临床表现进行综述与分析,并探讨其诊断分级与鉴别诊断,为制定职业性急性拟除虫菊酯中毒诊断标准提供参考。     

Do environmental and occupational exposure to pyrethroids and organophosphates affect human semen parameters? Results of a systematic review and meta-analysis

Our purpose was to review and analyse the impact of pyrethroids and organophosphates exposure on human semen parameters. A comprehensive literature search was performed through MEDLINE via PubMed, Scopus and Webscience. Only cohort studies examining semen parameters in workers or general populations exposed to pyrethroids or organophosphates were included. Ejaculate volume, sperm count, concentration, motility, viability, normal morphology and seminal pH alterations were pooled using the Cochran–Mantel–Haenszel Method with the random effect model and expressed as weighted mean difference, risk ratios, 95% confidence intervals and p-values. Seven cross-sectional studies regarding pyrethroids were included. Four of them were eligible for meta-analysis. The only parameter affected by pyrethroid exposure was normal sperm morphology (WMD-7,61%, 95%CI –11,92 to −3,30;p = 0,0,005). Nine studies were selected to evaluate the impact of organophosphates on semen parameters with six of them eligible for meta-analysis. A significant reduction was detected for the following: ejaculate volume (WMD −0,47ml, 95%CI −0,69 to −0,25; p < 0,0001), sperm count (WMD-40,03, 95%CI −66,81 to −13,25;p = 0,003), concentration (WMD-13,69 x10⁶/mL, 95%CI −23, 27 to-4,12;p = 0,005) and motility (WMD −5,70%, 95%CI −12,89 to 1,50;p = 0,12). Despite the increase in sperm abnormality, it has been shown that pyrethroids are unrelated to reduced sperm quality. However, the negative association of organophosphates with spermatogenesis is noteworthy.     

代谢解毒酶活性变化和击倒抗性基因突变在白纹伊蚊菊酯类杀虫剂抗性产生中的作用

目的 探讨代谢解毒酶活性变化和击倒抗性（kdr）基因突变在白纹伊蚊菊酯类抗性机制中的作用。方法 2017年8月至9月分别在山东省济南市千佛山公园（JN）、浙江省杭州市上茅家埠（HZ）、上海市宝山区宝山六村（BS）、上海市杨浦区共青森林公园（YP）和海南省海口市美兰区居民区（HK）采集现场白纹伊蚊（生物测定均为抗性种群）,检测其代谢解毒酶谷胱甘肽S-转移酶（GST）和多功能氧化酶（MFO）的活性并与敏感品系的白纹伊蚊比较,采用分类回归树方法（CART）分析GST和MFO活性变化及kdr突变（I1532和F1534）在抗性产生中的贡献率。结果 白纹伊蚊敏感品系的GST和MFO的活性基线水平均高于现场抗性种群BS和HK（P均<0.01）。BS种群接触溴氰菊酯后与未接触杀虫剂的基线相比,GST和MFO变化不明显（P>0.05）,接触氯菊酯后GST活性升高（P<0.05）,MFO活性也升高（P<0.01）;HK种群接触溴氰菊酯后GST活性差异不明显（P>0.05）、MFO活性升高（P<0.01）,接触氯菊酯后GST和MFO活性变化均不明显（P均>0.05）。5个现场抗性种群接触溴氰菊酯和氯菊酯后的GST和MFO活性与敏感品系的基线相比,变化无规律。CART分析结果显示,白纹伊蚊对溴氰菊酯的抗性产生中GST活性和kdr F1534突变的贡献率较大,其次是MFO活性,kdr I1532突变贡献率最小;对氯菊酯的抗性产生中,kdr F1534突变的贡献率最大,其次是GST和MFO活性,kdr I1532突变无贡献。结论 代谢解毒酶GST和MFO活性水平不适合作为判断白纹伊蚊种群对菊酯类杀虫剂抗性的单因素指标;代谢解毒酶活性变化和kdr突变可能是白纹伊蚊对菊酯类杀虫剂抗性产生中相互协同的2种机制。     

Origin and prevention of airport malaria in France

Summary Since 1969, 63 cases of airport malaria have been reported in Western Europe, 24 of which occurred in France. Most were due to Plasmodium falciparum . In 1994, 7 cases occurred in and around Roissy Charles de Gaulle airport (CDG), showing 4 types of contamination: among employees working on airstrips or opening containers, among residents living near the airport, among people living at some distance from the airport after a secondary transport of vectors, and by vectors transported in luggage. In-flight or stop-over infection is not considered as airport malaria. The infective anophelines originated from airports where malaria transmission occurs, mostly in subsaharan Africa. A tentative list is given taking into account aerial traffic with France. Surveys in the airports of Dakar (Senegal), Cotonou (Benin), Abidjan (Cote d'Ivoire) and Yaoundé (Cameroun) found potential vectors in all of these from July to September. After 1994, the Contrôle Sanitaire aux Frontières (CSF) in charge at CDG concentrated its efforts on the flights at risk, as well as information and sensitization of airline companies, which resulted in 73% and 87% of the flights at risk being properly disinsected in 1995 and 1996. Despite pyrethroid resistance in Anopheles gambiae s.s . in West Africa, the efficacy of aircraft spraying with permethrin aerosols is still acceptable. However, surveillance of resistance should be improved and search for nonpyrethroid insecticides suitable for aircraft strongly encouraged.     

三种拟除虫菊酯对低抗药性蟑螂现场防制研究

笔者采用ＷＨＯ蟑螂抗性测定方法，测定试验区美洲大蠊对溴氰菊酯的抗药性，并观察Ｃｒａｃｋｄｏｗｎ、凯素灵、奋斗呐对蟑螂滞留杀灭效果。该区蟑螂对溴氰菊酯属低度抗性；３种杀虫剂在使用剂量各为１５ｍｇ／ｍ２、１５ｍｇ／ｍ２及３０ｍｇ／ｍ２时，对蟑螂都有很好的滞留杀灭效果，而且Ｃｒａｃｋｄｏｗｎ有更快的击倒作用，施药后３个月，蟑螂密度被控制在很低的水平。     

Differential effects of pyrethroids on volume-sensitive anion and organic osmolyte pathways

1. There are no effective ways of screening for potential modulators of volume-regulated anion channels in their native cell type. Generally, cell lines are used for this purpose. Using HeLa and C6 glioma cells, we identified the pyrethroids as a novel class of compounds that inhibit taurine efflux through volume-regulated anion transport pathways in these cells. Subsequently, we examined their effects on volume-regulated anion channels in guinea-pig ventricular myocytes to determine whether results obtained using cell lines could be extrapolated to other tissues. 2. Tetramethrin inhibited taurine efflux in both HeLa and C6 glioma cells with Ki values of approximately 26 and 16 micro mol/L, respectively. Bioallethrin and fenpropathrin inhibited volume-sensitive taurine efflux from C6 glioma cells, but not from HeLa cells. The Ki values for bioallethrin and fenpropathrin were 70 and 59 micro mol/L, respectively. 3. Volume-sensitive I- efflux was observed in HeLa cells but not in C6 glioma cells, suggesting that the taurine efflux pathway in C6 glioma cells may be different to that of the I- efflux pathway. Cyfluthrin, tetramethrin, fenpropathrin, tefluthrin and bioallethrin all significantly inhibited volume-sensitive I- efflux from HeLa cells at 100 micro mol/L. 4. Patch-clamp experiments have shown inhibition of ICl,vol in guinea-pig ventricular myocytes by fenpropathrin, but not tetramethrin or cypermethrin, at 100 micro mol/L. This revealed that further differences exist between ICl,vol in guinea-pig ventricular myocytes and the anion transport pathways in C6 glioma and HeLa cells. 5. In conclusion, we have shown that pyrethroids differentially inhibit volume-regulated anion and taurine efflux in a number of cell types. Because these compounds have different effects in different cells, it is likely that: (i) more than one pathway is involved in the volume-sensitive transport of anions and organic osmolytes; and (ii) the molecular identities of the channels underlying anion transport are different. Finally, for the reasons given above, care should be taken when extrapolating data from one cell type to another. However, in the absence of an existing high-throughput screen, taurine efflux still represents a viable route for the identification of potential modulators of volume-regulated ion channels.