Standard WHO Procedure Research Articles

Relationship between G protein level with left ventricular systolic function in children with acyanotic heart disease.

Heart failure is a pediatric emergency caused by the heart's inability to adequately meet the body metabolic needs and the most common cause is congenital heart disease (CHD). The G protein is the most prominent family of membrane-bound protein known to act in major regulatory events of the cardiovascular system, one of which is heart failure. The aim of this study was to determine the level of G protein and its relationship with left ventricular systolic function in children with acyanotic CHD. A cross-sectional study was conducted in Dr. Zaionel Abidin Hospital, Banda Aceh, Indonesia. The patients aged 0 to 18 years and had acyanotic CHD diagnosis by echocardiography were included. Anthropometry measurement was performed according to standard WHO procedures and G protein level was measured using the ELISA method. The Chi-squared test was used to measure the relationship between G protein level and left ventricular systolic function. Out of a total of 38 children with acyanotic CHD, the mean level of G protein was 36.25 ng/mL and the mean of left ventricular systolic function was 73.1%. There was no relationship between G protein and left ventricular systolic function in children with acyanotic CHD. However, further study with a larger sample size and considering other variables are needed to confirm this finding.

Community evaluation of the physical and insecticidal durability of DuraNet® Plus, an alpha-cypermethrin and piperonyl butoxide incorporated mosquito net: protocol for a multi-country study in West, Central and East Africa

BackgroundPyrethroid-PBO nets have demonstrated improved impact against clinical malaria transmitted by pyrethroid resistant mosquito vectors and are being scaled up across Africa. However very little is known about their physical and insecticidal durability under operational conditions. This study will investigate the attrition, fabric integrity, insecticide content and bioefficacy of DuraNet® Plus, a new WHO prequalified alphacypermethrin and PBO incorporated net developed by Shobikaa Impex Private Limited over 3 years of field use in communities in Benin, Cameroon and Tanzania.MethodsThe study will be conducted in parallel in selected villages in Zakpota District in Benin, Mbalmayo, District in Cameroon and Muheza District in Tanzania. In each country, ~ 1800 households will be recruited and randomised to receive DuraNet® Plus or DuraNet® (a WHO prequalified alphacypermethrin-only ITN). Follow up surveys will be performed at 1 month post distribution to investigate adverse events and subsequently every 6–12 months to assess ITN attrition and fabric integrity following standard WHO procedures. A second cohort of nets will be withdrawn every 6–12 months and assessed for alpha-cypermethrin and PBO content and for entomological activity in laboratory bioassays (cone bioassays and tunnel tests). Alpha-cypermethrin bioefficacy will be monitored using the susceptible Anopheles gambiae Kisumu strain in cone bioassays while PBO bioefficacy will be monitored using pyrethroid resistant strains with overexpressed P450 enzymes in tunnel tests to determine the proportion of efficacious nets (≥ 95% knockdown, ≥ 80% mortality or ≥ 90% blood feeding inhibition in tunnels) at each time point. Nets withdrawn at 12, 24 and 36 months from each country will also be tested in experimental hut trials against wild free-flying pyrethroid resistant Anopheles gambiae sl in Côvè Benin to investigate the superiority of DuraNet® Plus over DuraNet® at each time point under semi field conditions.ConclusionThis large-scale multi country trial will provide useful information on the durability of a pyrethroid-PBO net (DuraNet® Plus) in 3 different regions in sub-Saharan Africa. The methods proposed for bioefficacy testing could also contribute towards the development of new standardised guidelines for monitoring the insecticidal efficacy of pyrethroid-PBO nets under operational conditions.

Comparison of Mosquito Larvicidal Formulations of Diflubenzuron on Culex Pipiens Mosquitoes in Belgrade, Serbia

Abstract Culex mosquitos are important infectious diseases vectors in temperate and tropical regions of the World, affecting nearly 350 million people in both developed and developing countries. Our approach was to “recycle” the well-established larvicide, and by studying the tablets, pellets and granules as floating or sinking formulations, we found a method to optimise the use of diflubenzuron against Culex pipiens mosquitoes in field conditions. A standard WHO procedure was used to test the larvicide efficacy. The combined efficacy of all floating formulations was 10.7% higher than sinking preparations (p-value =0.002) and that maximised throughout the experiment on days 14 and 21, (p-values 0.012 and 0.008, respectively). All floating formulations kept their efficacies above 70% until day 21 of the experiment, while the mortality of sinking designs dropped significantly after day 14. The lowest efficacy was observed when sinking granules were used and the highest when floating tablets were applied in the canals. Only the floating tablets showed no significant changes in efficacy from day 1 to 21, but then that efficacy drops sharp until day 35. Since the larvae spend most of their time on the surface of the slow-moving waters to breathe, and floating pellets and tablets are made of materials that can serve as food sources, we conclude that these formulations have a higher efficacy, at least in conditions of non- or slow-moving waters. This study shows the importance of a systematic approach to reformulation of old, already proven and environmentally safe larvicides which can control the mosquito populations and their spreading of various pathogens.

Susceptibility Status of Anopheles Gambiae S.I. to DDT and Permethrin in Lagos State, Nigeria.

Malaria is of public health importance in Nigeria and may retain its status, if new intervention methods are not introduced or the current ones monitored. This study was carried out in Alimosho, Kosofe, Ibeju-Lekki and Badagry Local Government Areas (LGAs) of Lagos State to assess the susceptibility status of Anopheles gambiae s.l., a dominant malaria vector in the localities to DDT 4% and Permethrin 0.75%. Anopheles larvae were collected from larva habitats in both LGAs, reared to adults and fed with 10% sucrose solution. Nonblood fed 2-5 days old female mosquitoes were exposed to discriminating doses of DDT and permethrin according to the standard WHO procedures. The knockdown effect was recorded at interval of 10 minutes and mortality scored 24hours after exposure. Species identification was done by morphological characteristics. Results from the study showed that Anopheles gambiae s.l. are resistant to DDT (4%) and permethrin (0.75%) with 24hr post exposure mortality ranging from 15.00-24.0% and 4.25-22.0% respectively. The Knockdown Time (KDT) ranged from 30.8-941.95minutes for DDT and 12.6-85.51minutes for permethrin. KDT95 50 ranges from 117.49-27524.22 minutes and 117.49-412.1 minutes for DDT and permethrin respectively. All the LGAs showed high level of resistance to DDT and permethrin. The high level of insecticide resistance recorded in this study could be detrimental to the elimination of malaria. Therefore, integrated vector management is needed to effectively carry out to manage the development of insecticide resistance.

First detection of SARS-CoV-2 in untreated wastewaters in Italy

Several studies have demonstrated the advantages of environmental surveillance through the monitoring of sewage for the assessment of viruses circulating in a given community (wastewater-based epidemiology, WBE).During the COVID-19 public health emergency, many reports have described the presence of SARS-CoV-2 RNA in stools from COVID-19 patients, and a few studies reported the occurrence of SARS-CoV-2 in wastewaters worldwide. Italy is among the world's worst-affected countries in the COVID-19 pandemic, but so far there are no studies assessing the presence of SARS-CoV-2 in Italian wastewaters. To this aim, twelve influent sewage samples, collected between February and April 2020 from Wastewater Treatment Plants in Milan and Rome, were tested adapting, for concentration, the standard WHO procedure for Poliovirus surveillance. Molecular analysis was undertaken with three nested protocols, including a newly designed SARS-CoV-2 specific primer set.SARS-CoV-2 RNA detection was accomplished in volumes of 250 ml of wastewaters collected in areas of high (Milan) and low (Rome) epidemic circulation, according to clinical data. Overall, 6 out of 12 samples were positive. One of the positive results was obtained in a Milan wastewater sample collected a few days after the first notified Italian case of autochthonous SARS-CoV-2.The study confirms that WBE has the potential to be applied to SARS-CoV-2 as a sensitive tool to study spatial and temporal trends of virus circulation in the population.

Increasing insecticide resistance in Anopheles funestus and Anopheles arabiensis in Malawi, 2011-2015.

BackgroundSusceptibility of principal Anopheles malaria vectors to common insecticides was monitored over a 5-year period across Malawi to inform and guide the national malaria control programme.MethodsAdult blood-fed Anopheles spp. and larvae were collected from multiple sites in sixteen districts across the country between 2011 and 2015. First generation (F1) progeny aged 2–5 days old were tested for susceptibility, using standard WHO procedures, against pyrethroids (permethrin and deltamethrin), carbamates (bendiocarb and propoxur), organophosphates (malathion and pirimiphos-methyl) and an organochlorine (DDT).ResultsMortality of Anopheles funestus to deltamethrin, permethrin, bendiocarb and propoxur declined significantly over the 5-year (2011–2015) monitoring period. There was wide variation in susceptibility to DDT but it was not associated with time. In contrast, An. funestus exhibited 100% mortality to the organophosphates (malathion and pirimiphos-methyl) at all sites tested. There was reduced mortality of Anopheles arabiensis to deltamethrin over time though this was not statistically significant. However, mortality of An. arabiensis exposed to permethrin declined significantly over time. Anopheles arabiensis exposed to DDT were more likely to be killed if there was high ITN coverage in the mosquito collection area the previous year. There were no other associations between mosquito mortality in a bioassay and ITN coverage or IRS implementation. Mortality of An. funestus from four sites exposed to deltamethrin alone ranged from 2 to 31% and from 41 to 94% when pre-exposed to the synergist piperonyl butoxide followed by deltamethrin. For permethrin alone, mortality ranged from 2 to 13% while mortality ranged from 63 to 100% when pre-exposed to PBO.ConclusionPyrethroid resistance was detected in An. funestus and An. arabiensis populations across Malawi and has worsened over the last 5 years. New insecticides and control strategies are urgently needed to reduce the burden of malaria in Malawi.Electronic supplementary materialThe online version of this article (doi:10.1186/s12936-016-1610-1) contains supplementary material, which is available to authorized users.

Adulticidal & larvicidal efficacy of three neonicotinoids against insecticide susceptible & resistant mosquito strains.

Background & objectives:Due to ever growing insecticide resistance in mosquitoes to commonly used insecticides in many parts of the globe, there is always a need for introduction of new insecticides for the control of resistant vector mosquitoes. In this study, larvicidal and adulticidal efficacies of three neonicotinoids (imidacloprid, thiacloprid and thiamethoxam) were tested against resistant and susceptible populations of Anopheles stephensi Liston 1901, Aedes (Stegomyia) aegypti Linnaeus, and Culex quinquefasciatus Say (Diptera: Culicidae).Methods:Laboratory-reared mosquito species were used. Insecticide susceptibility tests were done using standard WHO procedures and using diagnostic dosages of insecticide test papers and larvicides. Adulticidal efficacy of candidate insecticides was assessed using topical application method and larval bioassays were conducted using standard WHO procedure.Results:The results of topical application on 3-5 day old female mosquitoes indicated that resistant strain of An. stephensi registered lower LC50 values than the susceptible strain. Among the three insecticides tested, thiacloprid was found more effective than the other two insecticides. Culex quinquefasciatus registered lowest LC50 for imidacloprid than the other two mosquito species tested. In larval bioassays, the LC50 values registered for imidacloprid were in the order of Cx. quinquefasciatus <An. stephensi (SS) <An. stephensi (RR) <Ae. aegypti. In case of thiacloprid, the order of efficacy (LC50) was Cx. quinquefasciatus <An. stephensi (SS) <An. stephensi (RR), whereas in case of thiamethoxam, the larvicidal efficacy was in the order of An. stephensi (RR) <An. stephensi (SS) <Cx. quinquefasciatus.Interpretation & conclusions:The present study indicated that insecticide resistant strains of mosquito species tested showed more susceptibility to the three neonicotinoids tested, and the possibility of using neonicotinoids for the control of resistant mosquitoes should be explored.

Synthesis and larvicidal properties of benzophenone comprise indole analogues against Culex quinquefasciatus

With the increase of resistance to conventionally used existing synthetic insecticides, vector management has become extremely challenging. Hence more attention has been focused on newly synthesized benzophenone integrated indole analogues. Therefore our present study was aimed to evaluate the efficacy of synthesized benzophenone integrated indoles against the larvae of filariasis vector mosquitoes, Culex quinquefasciatus employing standard WHO procedure at Mysore. Among all the synthesized compounds the efficacy of compounds 7a, 7b and 7j seemed to be efficient with LC50 values of 9.17, 3.93 and 1.63 ppm respectively and LC90 values of 24.17, 8.85 and 6.17 ppm respectively. From the results, compounds 7a, 7b and 7j seemed could be considered as powerful candidates to bring about useful synthetic insecticides so as to prevent the resurgence of mosquito vectors.

Insecticide Resistance inAnopheles arabiensisfrom Ethiopia

The status of insecticide susceptibility of Anopheles arabiensis populations was monitored in northern and southern Ethiopia using one- to three-day-old mosquitoes reared from larval collections. Anopheles gambiae complex mosquitoes, identified by PCR as An. arabiensis, were exposed to diagnostic concentrations of DDT, malathion, fenitrothion, bendiocarb, propoxur and deltamethrin according to the standard WHO procedure. A heterogeneous and focal distribution of resistance phenotypes was observed in surveyed districts of the country. In Tach Armacho in northern Ethiopia, only resistance to DDT was detected. In the other two northern sites, An. arabiensis populations were susceptible to fenitrothion, resistant to malathion, propoxur and DDT and showed low levels of survival when exposed to bendiocarb requiring further investigations. In three areas of southern Ethiopia, An. arabiensis was susceptible to bendiocarb, propoxur and malathion, with low levels of survival on fenitrothion needing further confirma...

Composition and Larvicidal Activity of Artemisia Vulgaris L. Stem Essential Oil against Aedes Aegypti

This study investigates the composition and potential larvicidal activity of the essential oils isolated from the elite plant, Artemisia vulgaris L. which is commonly known as mugwort. Essential oils were hydrodistilled from in vitro raised stems and analysed by GC-MS. The major components of this oil were camphor, camphene, α-thujone, 1,8-cineole, γ-muurolene and β-caryophyllene. Mosquito larvicidal assays were carried out to test the efficacy of the oil against the dengue vector, Aedes aegypti. Laboratory reared third instar larvae were exposed to different concentrations of the oil solution and activity was assessed at different exposure times according to standard WHO procedure. Results showed that 100% larval mortality was achieved when the larvae were treated with 500 ppm oil solution with an exposure time of 8 h. The present study has shown that mugwort oil is a potential larvicide against Aedes aegypti even in low doses of the test solution. The results indicate that the natural insecticides could be used in the place of synthetic insecticides and save our environment from chemical hazards.

Status of carbohydrate, protein and lipid profile in the mosquito larvae treated with certain phytoextracts

Objective To investigate the impact of the most potent petroleum ether extract of Artemisia annua (A. annua) and Azadirachta indica (Az. indica) on total carbohydrate, lipid and protein level of Anopheles stephensi and Culex quinquefasciatus larvae. Methods Mosquito larvae were exposed to the extracts selected as per standard WHO procedure. Carbohydrate (glucose), total lipid and protein were estimated by the methods as Nelson, Bragdon and Lowry described, respectively. Results The glucose levels were increased to 27.87% and 46.8%, respectively in anopheline larval tissues after treatment with petroleum ether extract of A. annua and methanolic extract of Az. indica. In culicine larvae, glucose levels were reduced to 58.96% and 24.65%, respectively. After treatment with A. annua extract, lipid contents in anopheline and culicine larvae decreased by 28.57% and 25.0%, respectively and increased by 14.29% and 50.00% in the Anopheles and Culex larvae, respectively after treatment with methanolic extract of Az. indica. Total protein levels were reduced to 63.13% and 92.62% in anopheline and to 32.39% and 48.12% in culicine larvae after treatment with A. annua and Az. Indica extracts, respectively. Conclusions Two extracts produce significant alterations in the biochemical profiles of anopheline and culicine larvae. Further, the impacting factors of extracts on carbohydrate, lipid and protein contents of larvae are species and specific extraction. It indicates the disturbed metabolic activity of the larvae.

Bioactivity guided isolation of mosquito larvicide from Piper longum

Objective To isolate the larvicidal component from the fruits of Piper longum (P. longum) against the filariasis vector, Culex quinquefasciatus (C. quinquefasciatus). Methods Pulverized fruits of P. longum were subjected to soxhlet extraction using series of organic solvents of increasing polarity. All the solvent extracts were verified for their larvicidal efficacy against 4th instar larvae of C. quinquefasciatus employing standard WHO procedure. Bioassay-guided fractionation through column chromatography lead to the isolation of a bioactive amide, pipyahyine from the petroleum ether extract. Results Petroleum ether extract was found to be the most active fraction among all the extracts tested with LC 50 and LC 90 being 1.03 and 2.04 ppm respectively. Whereas, pipyahyine, an isolated component of the same fraction was found to be even more effective than the parent extract in terms of LC 50 being 0.58 and 1.88 ppm respectively. Conclusions From the results, it is evident that P. longum can be considered as a powerful arsenal for the control of mosquito population.

Trends in DDT and pyrethroid resistance in Anopheles gambiae s.s. populations from urban and agro-industrial settings in southern Cameroon.

BackgroundPyrethroid insecticides are widely used for insect pest control in Cameroon. In certain insect species, particularly the malaria vector Anopheles gambiae, resistance to this class of insecticides is a source of great concern and needs to be monitored in order to sustain the efficacy of vector control operations in the fields. This study highlights trends in DDT and pyrethroid resistance in wild An. gambiae populations from South Cameroon.MethodsMosquitoes were collected between 2001 and 2007 in four sites in South Cameroon, where insecticides are used for agricultural or personal protection purposes. Insecticide use was documented in each site by interviewing residents. Batches of 2-4 days old adult female mosquitoes reared from larval collections were tested for susceptibility to DDT, permethrin and deltamethrin using standard WHO procedures. Control, dead and survivors mosquitoes from bioassays were identified by PCR-RFLP and characterized for the kdr mutations using either the AS-PCR or the HOLA method.ResultsFour chemical insecticide groups were cited in the study sites: organochlorines, organophosphates, carbamates and pyrethroids. These chemicals were used for personal, crop or wood protection. In the four An. gambiae populations tested, significant variation in resistance levels, molecular forms composition and kdr frequencies were recorded in the time span of the study. Increases in DDT and pyrethroid resistance, as observed in most areas, were generally associated with an increase in the relative frequency of the S molecular form carrying the kdr mutations at higher frequencies. In Mangoum, however, where only the S form was present, a significant increase in the frequency of kdr alleles between 2003 to 2007 diverged with a decrease of the level of resistance to DDT and pyrethroids. Analyses of the kdr frequencies in dead and surviving mosquitoes showed partial correlation between the kdr genotypes and resistance phenotypes, suggesting that the kdr mechanism may act with certain co-factors to be identified.ConclusionThese results demonstrate the ongoing spread of kdr alleles in An. gambiae in Central Africa. The rapid evolution of insecticide resistance in this highly dynamic and genetically polymorphic species remains a challenge for its control.

Efficacy of bioactive compounds from Curcuma aromatica against mosquito larvae

With the development of resistance to conventionally used synthetic insecticides, vector management has become acutely problematic. Hence more attention has been focused on botanicals. Therefore our present study was aimed to evaluate the efficacy of extracts from rhizomes of Curcuma aromatica against the larvae of filariasis vector mosquitoes, Culex quinquefasciatus employing standard WHO procedure at Mysore. The soxhlet extraction was carried out using non-polar organic solvent, petroleum ether. The efficacy of petroleum ether extract seemed to be effective with LC 50 and LC 90 values of 11.42 and 18.00 ppm respectively. Bioassay-guided fractionation through flash chromatography lead to the isolation of two larvicidal compounds namely 9-oxoneoprocurcumenol and neoprocurcumenol. Between the two, 9-oxoneoprocurcumenol exerted significant toxicity ( P < 0.01) on mosquito larvae with LC 50 value of 5.81 ppm and LC 90 being 9.99 ppm compared to neoprocurcumenol with 13.69 and 23.92 ppm of LC 50 and LC 90 values respectively. From the results, C. aromatica could be considered as one of the powerful candidate to bring about useful botanicals so as to prevent the resurgence of mosquito vectors.

Utilization, retention and bio-efficacy studies of PermaNet in selected villages in Buie and Fentalie districts of Ethiopia.

BackgroundMalaria remains a major public health problem in Ethiopia. Pyrethroid-treated mosquito nets are one of the major tools available for the prevention and control of malaria transmission. PermaNet® is a long-lasting insecticide-treated net (LLIN) recommended by WHO for malaria control.ObjectiveThe objective of the study was to assess utilization and retention of PermaNet® nets distributed for malaria control in Buie and Fentalie districts and monitor the bio-efficacy of the nets using the WHO cone bioassay test procedures.MethodsA cross sectional study was carried out by interviewing household heads or their representative in Buie and Fentalie districts. The two districts were selected based on a priori knowledge of variations on ethnic background and housing construction. Clusters of houses were chosen within each of the study villages for selection of households. 20 households that had received one or more PermaNet® nets were chosen randomly from the clusters in each village. A total of eight used PermaNet® nets were collected for the bio-efficacy test. The bio-efficacy of PermaNet® nets was monitored according to the standard WHO procedures using a susceptible colony of Anopheles arabiensis to deltamethrin.ResultsA total of 119 household heads were interviewed during the study. The retention rate of nets that were distributed in 2005 and 2006 season was 72%. A total of 62.2% of the interviewees claimed children under five years of age slept under LLIN, while only 50.7% of the nets were observed to be hanged inside houses when used as a proxy indicator of usage of LLIN. For the bio-efficacy test the mean knock-down was 94% and 100%, while the mean mortality rate observed after 24 hr holding period was 72.2% and 67% for Buie and Fentalie districts respectively.ConclusionThe study revealed a moderately high retention of PermaNet® in the study villages and effectiveness of the nets when tested according to the standard WHO procedure.

Sulfadoxine–pyrimethamine plus artesunate compared with chloroquine for the treatment of vivax malaria in areas co-endemic for Plasmodium falciparum and P. vivax: a randomised non-inferiority trial in eastern Afghanistan

Chloroquine (CQ) is an effective treatment of choice for vivax malaria in most settings, but with the spread of CQ-resistant Plasmodium falciparum, many countries now use artemisinin-based combination therapy for treatment of falciparum malaria. In areas co-endemic for falciparum and vivax malaria incorrect differential diagnosis is always a risk. In Afghanistan the adoption of sulfadoxine-pyrimethamine plus artesunate (SP+AS) as first-line falciparum treatment raises the prospect of a significant proportion of vivax malaria being misdiagnosed and treated with the combination. SP is considered to have limited efficacy against vivax malaria, and the efficacy of SP+AS against Plasmodium vivax has not been established in areas that are using SP+AS. A randomised, non-inferiority trial comparing SP+AS with CQ monotherapy was undertaken on 190 vivax malaria patients in eastern Afghanistan. Standard WHO procedures for in vivo evaluation of antimalarial drugs were followed. A total of 180 individuals completed the trial to day 42. Using a per protocol analysis, both regimens resulted in > or =96% treatment success at 28 d, but significantly more cases failed in the CQ arm (46%) than in the SP+AS arm (24%) by day 42. In areas where vivax infections might be misdiagnosed as falciparum infections and treated with SP+AS, patient management would be as good, or better than, with the standard CQ treatment.

Evaluation of KO-Tab 1-2-3®: a wash-resistant 'dip-it-yourself' insecticide formulation for long-lasting treatment of mosquito nets

IntroductionInsecticide-treated nets (ITN) are an important method of preventing malaria. To remain effective, they need to be re-treated with pyrethroid insecticide at approximately yearly intervals. Systems for re-treating nets in Africa are limited, and the vast majority of nets in use have never been treated or were treated only once. Bayer Environmental Science (BES) has developed a long-lasting formulation 'KO-Tab 1-2-3®' which can be applied to the net post-manufacture, under field conditions, and renders the insecticide wash-resistant.MethodsThe performance of polyester nets treated with three kinds of BES long-lasting formulations, a conventional ITN (treated with standard KO-Tab) and PermaNet 2.0 were evaluated after washing samples of treated netting up to 30 times using standard WHO procedures. Performance was measured using 'three-minute exposure' and 'median time to knockdown' bioassay tests and by measuring the levels of deltamethrin using high-pressure liquid chromatography.ResultsThe conventional ITN was largely stripped of deltamethrin within 5–10 washes and insecticidal efficacy in bioassay declined to suboptimal levels. With PermaNet and KO-Tab 1-2-3 the loss of deltamethrin was much slower: insecticide content halved within 20 washes and there was no loss of biological efficacy in three-minute exposure bioassays in WHO cylinders even after 30 washes. After 30 washes there remained on the netting 16% (4.4 mg/m2) of the loading dose of KO-Tab 1-2-3 and 28% (18.8 mg/m2) of the loading dose of PermaNet.ConclusionKO-Tab 1-2-3 was confirmed to be a long-lasting insecticide formulation. This finding raises the prospect of conventional polyester nets being converted into long-lasting insecticidal nets through simple dipping in the community or at home. This single development, if widely adopted, could transform the malaria control landscape in Africa and have a major impact on malaria.

Distribution of the molecular forms of Anopheles gambiae and pyrethroid knock down resistance gene in Nigeria

We investigated the distribution of the molecular M and S forms of Anopheles gambiae and the knock down resistance ( kdr) gene associated with pyrethroid and DDT resistance in A. gambiae s.s. at 13 localities across Nigeria. Two–three days old adult female mosquito reared from larval collections were tested using standard WHO procedures, diagnostic test kits and impregnated papers to assess their pyrethroid resistance status. Specimens were identified by PCR assays and characterized for the kdr gene. DNA from adult A. gambiae s.s. collected from human dwellings were also tested for the presence of the kdr gene. The overall collection was a mix of the molecular M and S forms across the mangrove (63:37%), forest (56:44%), and transitional (36:64%) ecotypes, but almost a pure collection of the S form in the Guinea and Sudan-savanna. Results of insecticide susceptibility tests showed that mosquitoes sampled at seven localities were susceptible to permethrin, deltamethrin, and DDT, but populations of A. gambiae resistant to these insecticides were recorded at six other localities mainly in the transitional and Guinea-savanna ecotypes. The kdr gene was found only in the molecular S forms, including areas where both forms were sympatric. The overall kdr frequency was low: <47% in forest, 37–48% in the transitional, and 45–53% in Guinea-savanna. The data suggest that pyrethroid resistance in A. gambiae in Nigeria is not as widespread when compared to neighbouring West African countries.

Absence of the kdr mutation in the molecular 'M' form suggests different pyrethroid resistance mechanisms in the malaria vector mosquito Anopheles gambiae s.s.

Field tests conducted on adult Anopheles mosquitoes using standard WHO procedures, diagnostic kits and test papers in south-western Nigeria showed pyrethroid (deltamethrin and permethrin) resistance in adult populations of Anopheles gambiae sensu stricto. The knock-down resistance (kdr) mutation involved in pyrethroid resistance was only found in the molecular S form of An. gambiae s.s. even in area where both molecular M and S forms occurred in sympatry. The absence of the kdr mutation in the M form suggests an additional pyrethroid resistance mechanism in An. gambiae s.s.

Dehydrochlorination of DDT by Asian blood-sucking leeches.

Summary The toxicity of DDT for Southeast Asian buffalo leeches, Hirudinaria manillensis, was tested with a modification of the standard WHO procedures for determining susceptibility-resistance of mosquito larvae to insecticides. Specimens of H. manillensis from Bangkok, Thailand, and Kuala Lumpur, Malaysia, showed a high degree of tolerance. LC50 values after 120 hours' continuous exposure were 100 ppm for leeches from Kuala Lumpur and 60 ppm for specimens from Bangkok. The absorption of DDT by specimens of Hirudo nipponia from Japan and of H. manillensis from Malaysia was determined by radioactive assessment of chloroform extracts of leeches that had been exposed for 24 hours in aqueous solution containing 7.1 ppm of ringlabeled C14 DDT. Results showed that 16% of exposed DDT was recovered from H. nipponia, and 17.4% from H. manillensis. After assessment of absorption of DDT by the leeches, the chloroform extracts were evaporated to dryness, taken up in acetone, and chromatographed. The chromatogram of H. nipponia extract showed that 49% of the absorbed DDT had been converted to the nontoxic DDE. Chromatograms of extracts by H. manillensis showed neither production of DDE nor other metabolites of DDT analogues. This, as far as could be determined, was the first demonstration of dehydrochlorination of DDT by an annelid.