Screening of household contacts for TB infection in Cote d'Ivoire.

SETTING: Côte d'Ivoire is a country with a high incidence of TB. The control of TB infection is focused on high-risk patients but has limited implementation. OBJECTIVE: Cost-benefit analysis of TB infection (TBI) screening of household contacts in Côte d'Ivoire to evaluate economic implications of the implementation of interferon-gamma release assays (IGRAs) and the tuberculin skin test (TST). DESIGN: We compared the effectiveness of QuantiFERON-TB Gold Plus (QuantiFERON) with the TST using an economic model previously evaluated in medium TB incidence settings. Principal outcomes relating to TBI screening, as well as the lifetime costs and benefits of the patient cohort, were captured using a decision tree, followed by a Markov model. RESULTS: QuantiFERON proved to be both more effective and less costly than TST. Compared to QuantiFERON, TST use leads to an approximate 33% increase in the lifetime risk of developing active TB. CONCLUSIONS: For household contacts of active TB cases in Côte d'Ivoire, QuantiFERON is cost-effective when compared with TST. R shiny interactive interface enables model customisation for different scenarios, settings, risk groups and TBI screening methods. Further research should be conducted in similar settings to generalise the results.

CONTEXTE: La Côte d'Ivoire est un pays où l'incidence de la TB est élevée. La lutte contre l'infection à TB est axée sur les patients à haut risque, mais sa mise en œuvre est limitée. OBJECTIF: Analyse coût-bénéfice du dépistage de l'infection à TB (TBI) chez les contacts familiaux en Côte d'Ivoire afin d'évaluer les implications économiques de la mise en œuvre des tests de libération de l'interféron-gamma (IGRA) et du test cutané à la tuberculine (TST). DESIGN: Nous avons comparé l'efficacité de QuantiFERON-TB Gold Plus (QuantiFERON) avec celle du TST en utilisant un modèle économique précédemment évalué dans des contextes d'incidence moyenne de la TB. Les principaux résultats relatifs au dépistage de la TBI, ainsi que les coûts et bénéfices à vie de la cohorte de patients, ont été saisis à l'aide d'un arbre de décision, suivi d'un modèle de Markov. RÉSULTATS: QuantiFERON s'est avéré à la fois plus efficace et moins coûteux que le TST. Par rapport à QuantiFERON, l'utilisation du TST entraîne une augmentation d'environ 33% du risque de développer une TB active au cours de la vie. CONCLUSIONS: Pour les contacts familiaux des cas de TB active en Côte d'Ivoire, QuantiFERON est rentable par rapport au TST. L'interface interactive R shiny permet de personnaliser le modèle pour différents scénarios, contextes, groupes à risque et méthodes de dépistage de la TBI. D'autres recherches devraient être menées dans des contextes similaires pour généraliser les résultats.

[Value of gastric fluid to start antibiotics in premature babies suspected of having early neonatal bacterial infection]. / Intérêt du liquide gastrique dans la décision d'antibiothérapie du nouveau-né prématuré suspect d'infection bactérienne précoce.

The objective of this study was to evaluate the value of direct examination and culture of gastric fluid in the treatment of early neonatal bacterial infections (INBP) in pre-term infants. MATERIALS AND METHODS: Observational study conducted over 6 months in a Type III center. All hospitalized premature babies who had routine gastric fluid sampling at birth during the period of the study were included. They were classified into two groups: premature infants with probable or suspected infection and treated as such (Group 1) and premature infants with no infection or only having colonization (Group 2). RESULTS AND DISCUSSION: In total, 255 pre-term infants were included in the study. Group 1 consisted of 127 newborns and group 2 consisted of 128 newborns. The direct gastric fluid examination was positive in 51 newborns in Group 1 and in 46 newborns in group 2. The culture was positive in 25 newborns in group 1 and eight newborns in group 2. Direct examination of gastric fluid of the 255 children studied had low sensitivity (40.1%) and low specificity (64%) of INBP, with 52.6% positive predictive value (PPV) and 51.8% negative predictive value (NPV). The gastric fluid culture was specific (93.7%) of the INBP, sensitivity was low (19.6%), with PPV at 75.7% and NPV at 54%. CONCLUSION: These results undermine the relevance of the direct examination of gastric fluid in the delicate diagnosis of INBP. This direct examination has a low PPV and NPV. It is advisable not to start or stop antibiotic therapy solely on this argument; however, it can guide the choice of antibiotic therapy and remains useful for this reason. The culture of gastric fluid has very good specificity (93.7%).

[Use of the Xpert® MTB/RIF test in routine screening of new cases of pulmonary tuberculosis in an endemic area]. / Test Xpert® MTB/RIF et dépistage des nouveaux cas de tuberculose pulmonaire en routine dans une zone de haute endémicité tuberculeuse.

BACKGROUND: Developed initially for the diagnosis of multidrug-resistant tuberculosis, the Xpert® MTB/RIF test has shown to be useful for the diagnosis of tuberculosis, especially among HIV-infected subjects. The objective of the study was to determine the contribution of the Xpert® MTB/RIF test for routine pulmonary tuberculosis diagnosis in an endemic area. METHODOLOGY: We undertook a prospective study among patients presenting with cough and sputum. The sputum was submitted to microscopic examination, to the Xpert® MTB/RIF test and cultured by the Mycobacteria growth indicator tube (MGIT) technique. The study compared cases of pulmonary tuberculosis confirmed by a positive sputum culture and cases with cough but negative sputum culture. RESULTS: In multivariate analysis, the factors associated with positive cultures were the following: male gender, cough for more than 2 weeks, loss of weight and fever. The estimated clinical suspicion score consisted of 4 signs each having a coefficient of 1. The sensitivity of each clinical sign varied between 79 and 94%. In 348 cases of negative microscopic examination (composed of 295 cases with score<4 and 53 cases with score=4), the predictive positive value of the Xpert® MTB/RIF was 80% for a score equal to 4 and 40.9% for a score<4. In cases of negative microscopic examination of the sputum, the Xpert® MRT/RIF test should be undertaken if the score=4. CONCLUSION: The diagnosis of tuberculosis in endemic zones could be improved by using the Xpert® MTB/RIF.

Social determinants associated with Giardia duodenalis infection in southern Côte d'Ivoire.

The purpose of this investigation was to analyze the association between different social determinants of health at the local scale and Giardia duodenalis infection in diverse settlements in southern Côte d'Ivoire. Stool samples from 306 individuals aged 1-16 years were collected from six rural villages and a small town. Five variables were categorized to classify the increasing risk levels of acquiring intestinal parasites. Giardia prevalences (%) and odds ratios (ORs) were evaluated. Correlation and regression analyses were conducted to determine the correlation coefficients and to propose predictive models based on social determinants to forecast the risk of giardiasis. The overall observed prevalence of Giardia was 21.6 %. When the analysis was conducted at the local level, the percentage of infected people varied from a minimum of 12.7 up to 36.4 %. A significant association (p < 0.001) was found between the selected social determinants and G. duodenalis prevalence in the different localities. Correlation and regression analyses allowed us to describe two predictive models to estimate the OR of Giardia transmission. This study helps to clarify the possible impact of different social determinants of health on the risk of giardiasis at the local scale. Both predictive models could be suitable in order to assess the likelihood of the transmission of intestinal parasitic infection in developing countries.

[Epidemiology of bacterial infection materno-fetal at Abidjan- Ivory Cost: prospective study of eighty (80) cases]. / Epidemiologie de l'infection bacterienne materno-fœtale a Abidjan-Cote d'Ivoire: etude prospective a propos de 80 cas.

The aim of our study was to describe the risk factors, clinical symptoms and bacteria isolated during fetal-maternal bacterial infections in hospitals. MATERIALS AND METHODS: This was a prospective, descriptive study conducted from August 2, 2007 to October 3, 2007 at the neonatology department and the delivery room of the Yopougon teaching hospital . All newborn babies presenting a risk factor of infection have been included in this study. A bacteriological evaluation including containing central, peripheral and gastric fluid samples was performed. Bacteriological tests (NFS, CRP, PCT) were also performed on those newborn babies. RESULTS: Eighty newborn babies were included. The maternal risk factors were dominated by prolonged breaking of membranes 62.5%. In the newborn bad APGAR score 56.3% and prematurity 18.8%, were noted. The main clinical symptoms were neurological, , respiratory and digestive 52.5%, 44.4% 37.5%, respectively. The main pathogens isolated were 65.5% Staphylococcus coagulase negative, 13.8% Staphylococcus aureus, 6.9% Pseudomonas aeruginosa, 3,4% Klebsiella pneumoniae, and 3.4% Acinetobacter Sp. CONCLUSION: The clinical symptoms of the fetal-maternal bacterial infections are polymorphic. Germs found in our study differ from those usually found in the fetal-maternal bacterial infections in Europe.

L'objectif de notre étude était de décrire les facteurs de risques, la symptomatologie clinique et les bactéries isolées au cours des infections bactériennes materno-fœtales (IBMF) en milieu hospitalier. MATÉRIEL ET MÉTHODES: Il s'agissait d'une étude prospective à visée descriptive menée du 2 août 2007au 3 octobre 2007 dans le service de néonatalogie et la salle d'accouchement du CHU de Yopougon. Tous les nouveau-nés présentant un facteur de risque infectieux ont été inclus dans l'étude. Un bilan bactériologique comportant des prélèvements centraux, périphériques et liquide gastrique à été effectué. Un bilan biologique (NFS, CRP, PCT) a également été réalisé chez ces nouveau-nés. RÉSULTATS: Quatre vingt nouveau-nés ont été inclus. Les facteurs de risques maternels étaient dominés par la rupture prolongée des membranes 62,5%. Chez le nouveau-né on notait le mauvais APGAR 56,3 %, la prématurité 18,8%. Les principales manifestations cliniques étaient neurologiques 52,5%, respiratoires 44,4% et digestifs 37,5%. Les principaux germes isolés étaient Staphylocoque coagulase négative 65 ,5%, Staphyloccus aureus 13,8%, Pseudomonas aeruginosa 6,9%; Klebsiella pneumoniae 3,4 %; Acinetobacter Sp 3,4%. CONCLUSION: La symptomatologie clinique des IBMF est polymorphe. Les germes retrouvés au cours de notre étude diffèrent de ceux habituellement retrouvés au cours des IBMF en Europe.

Evaluation of indoor residual spraying with the pyrrole insecticide chlorfenapyr against pyrethroid-susceptible Anopheles arabiensis and pyrethroid-resistant Culex quinquefasciatus mosquitoes.

Chlorfenapyr is a pyrrole insecticide with a unique non-neurological mode of action. Laboratory bioassays of chlorfenapyr comparing the mortality of pyrethroid-susceptible and -resistant Anopheles gambiae s.s. and Culex quinquefasciatus mosquitoes indicated that operational cross-resistance is unlikely to occur (resistance ratio ranged between 0 and 2.1). Three trials of chlorfenapyr indoor residual spraying were undertaken in experimental huts in an area of rice irrigation in northern Tanzania that supports breeding of A. arabiensis. Daily mosquito collections were undertaken to assess product performance primarily in terms of mortality. In the second trial, 250mg/m(2) and 500mg/m(2) chlorfenapyr were tested for residual efficacy over 6 months. Both dosages killed 54% of C. quinquefasciatus, whilst for A. arabiensis 250mg/m(2) killed 48% compared with 41% for 500mg/m(2); mortality was as high at the end of the trial as at the beginning. In the third trial, 250mg/m(2) chlorfenapyr was compared with the pyrethroid alpha-cypermethrin dosed at 30mg/m(2). Chlorfenapyr performance was equivalent to the pyrethroid against A. arabiensis, with both insecticides killing 50% of mosquitoes. Chlorfenapyr killed a significantly higher proportion of pyrethroid-resistant C. quinquefasciatus (56%) compared with alpha-cypermethrin (17%). Chlorfenapyr has the potential to be an important addition to the limited arsenal of public health insecticides for indoor residual control of A. arabiensis and pyrethroid-resistant species of mosquito.

Is K-O Tab 1-2-3((R)) long lasting on non-polyester mosquito nets?

Many societies use locally sourced mosquito nets made from a variety of materials. For protecting against malaria these require regular re-treatment with insecticide. K-O Tab 1-2-3 is a 'dip-it-yourself' long-lasting formulation with time-limited interim recommendation from WHO for treatment of washed white and coloured polyester nets for up to 15 washes. To determine wash-resistance on different fabrics, nets made of polyester, polyethylene, cotton or nylon were treated with K-O Tab 1-2-3 and washed up to 20 times using standard WHO washing procedures. Efficacy was assessed using cone and cylinder bioassays and tunnel tests, and deltamethrin content using high-pressure liquid chromatography. Polyethylene and cotton nets treated with K-O Tab 1-2-3 and washed 20 times achieved the WHO threshold of >80% mortality in tunnel tests. Polyethylene matched the performance of polyester in all bioassays in contrast to cotton and nylon which produced low mortality and knock-down in cone and cylinder bioassays. After 20 washes 16.5% of the loading dose of deltamethrin remained on the polyester nets compared with 28.7% on polyethylene, 38.9% on cotton and 2.2% on nylon. Cotton nets retained a high concentration of insecticide but the relatively poor performance in terms of knock-down and mortality suggest most insecticide is bound within the cotton fibres rather than on the surface. K-O Tab 1-2-3 renders insecticide wash fast on polyethylene nets, less so on cotton and nylon. Nets made from polyethylene can be treated in the home to render the insecticide long lasting.

[Epidemiological study of the malaria at the neonatal period in the teaching hospital of Yopougon--Republic of Cote d'Ivoire]. / Etude epidemiologique du paludisme dans la periode neonatale au Centre Hospitalier Universitaire (CHU) de Yopougon Republique de Cote D'Ivoire.

PURPOSE: Malaria is rare at the newborn child's, even in zone of endemic disease, so that its research is not systematic at this age. Our study aims to describe the profile of the malaria during the neonatal period. PATIENTS AND METHODS: The retrospective and descriptive study, concerned the files of the newborn children hospitalized from 2005/02/01 till 2006/03/31, in the department of Neonatology at the teaching hospital of Yopougon in Abidjan û Côte d'Ivoire. The criteria of inclusion were fever, associated or not with other symptoms and positive thick drop and or blood smear. The criterion of exclusion was the positivity of the biological explorations for infection. The studied parameters took into account epidemiology, symptomatology, biology and therapeutics. RESULTS: Prevalence of neonatal malaria was 0.98 per cent (6/615) according to our study. Except the fever which was a criterion of inclusion, the paleness was the dominant symptom. Four of our patients had a history of blood transfusion and 3 among these had a postnatal severe malaria, with highest parasitemia and lowest rates of haemoglobin. Quinine was the most used treatment. CONCLUSION: It is important in zone of endemic malaria disease, to make at the newborn child's, often and easily, thick drop and blood smear, especially when there is a history of blood transfusion.

Etude épidemiologique du paludisme dans la periode néonatale au centre hospitalier universitaire (CHU) de Yopougon République de Côte d'Ivoire

But : Le paludisme est une affection rare chez le nouveau-ne; meme en zone d'endemie; de sorte que sa recherche n'est pas systematique a cet age. Notre etude vise a decrire le profil du paludisme pendant la periode neonatale. Patients et methodes : L'etude descriptive retrospective; a porte sur les dossiers des nouveau-nes hospitalises du 01/02/2005 au 31/03/2006; dans le service de Neonatologie du centre hospitalier universitaire (CHU) de Yopougon a Abidjan; Cote d'Ivoire. Les criteres d'inclusion etaient la fievre; isolee ou non et une goutte epaisse/frottis sanguin (GE/FS) positive. Le critere d'exclusion etait la positivite du bilan biologique d'infection. Les parametres etudies prenaient en compte l'epidemiologie; la clinique; la biologie et la therapeutique. Resultats : La prevalence du paludisme neonatal etait de 0;98(6/615) selon notre etude. Hormis la fievre qui etait un critere d'inclusion; la paleur etait le symptome dominant. Quatre de nos patients avaient un antecedent de transfusion sanguine et 3 parmi ceux-ci avaient un paludisme grave postnatal; avec les plus fortes parasitemies et les plus bas taux d'hemoglobine. Les sels de quinine ont ete le traitement le plus utilise. Conclusion : Il importe en zone d'endemie; d'avoir la goutte epaisse facile chez le nouveau-ne et ce; d'autant qu'il existe un antecedent de transfusion sanguine

[Generalized tetanus with otitic portal of entry after using intra-auricular traditional remedies in a 2 old child]. / Tetanos généralisé à porte d'entrée otitique, suite à l'utilisation de topiques traditionnels intra-auriculaires chez un enfant de 2 ans.

A case of tetanus with uncommon way of contamination was found in the paediatric department of the Yopougon teaching hospital in Côte d'Ivoire. A two-year-old child, without vaccination against tetanus and suffering from a chronic otitis presented a generalized tetanus, after the use of traditional local remedies in his ear. Through this observation, the authors want to make population aware of the detrimental effects of traditional local auricular remedies and want to advise all physicians to make a serotherapy and/or a vaccination against tetanus to all children with chronic otitis in our area.

Loss of protection with insecticide-treated nets against pyrethroid-resistant Culex quinquefasciatus mosquitoes once nets become holed: an experimental hut study.

BACKGROUND: An important advantage of pyrethroid-treated nets over untreated nets is that once nets become worn or holed a pyrethroid treatment will normally restore protection. The capacity of pyrethroids to kill or irritate any mosquito that comes into contact with the net and prevent penetration of holes or feeding through the sides are the main reasons why treated nets continue to provide protection despite their condition deteriorating over time. Pyrethroid resistance is a growing problem among Anopheline and Culicine mosquitoes in many parts of Africa. When mosquitoes become resistant the capacity of treated nets to provide protection might be diminished, particularly when holed. An experimental hut trial against pyrethroid-resistant Culex quinquefasciatus was therefore undertaken in southern Benin using a series of intact and holed nets, both untreated and treated, to assess any loss of protection as nets deteriorate with use and time. RESULTS: There was loss of protection when untreated nets became holed; the proportion of mosquitoes blood feeding increased from 36.2% when nets were intact to between 59.7% and 68.5% when nets were holed to differing extents. The proportion of mosquitoes blood feeding when treated nets were intact was 29.4% which increased to 43.6-57.4% when nets were holed. The greater the number of holes the greater the loss of protection regardless of whether nets were untreated or treated. Mosquito mortality in huts with untreated nets was 12.9-13.6%; treatment induced mortality was less than 12%. The exiting rate of mosquitoes into the verandas was higher in huts with intact nets. CONCLUSION: As nets deteriorate with use and become increasingly holed the capacity of pyrethroid treatments to restore protection is greatly diminished against resistant Culex quinquefasciatus mosquitoes.

Chlorfenapyr: a pyrrole insecticide for the control of pyrethroid or DDT resistant Anopheles gambiae (Diptera: Culicidae) mosquitoes.

Owing to the development and spread of pyrethroid resistance in Anopheles gambiae in Africa there is an urgent need to develop alternative insecticides to supplement the pyrethroids. Chlorfenapyr is a pyrrole insecticide first commercialized for the control of agricultural pests and termites. Performance against An. gambiae bearing kdr (pyrethroid and DDT resistance) or Ace-1(R) insensitive acetylcholinesterase (organophosphate and carbamate resistance) mechanisms was studied using a variety of adult bioassay tests including a simulated-experimental hut system (tunnel tests) that allows uninhibited mosquito behaviour/insecticide interactions. Strains resistant to pyrethroids and organophosphates showed no cross resistance to chlorfenapyr. In cone bioassays on treated netting the mortality of adult mosquitoes showed an unexpected curvilinear response, with highest mortality occurring at intermediate dosages. Adults expressed irritability to chlorfenapyr at higher dosages, which might explain the dosage-mortality trend. Toxic activity of chlorfenapyr was slow compared to conventional neurotoxic insecticides and additional mortality occurred between 24h and 72 h. In tunnel tests, the dosage-mortality trend showed a more typical sigmoid response and most mortality occurred during the first 24h. Mosquito penetration through the holed, treated netting showed only limited inhibition and blood-feeding was not inhibited. Mortality rates in the kdr strain exposed to chlorfenapyr treated netting in tunnel tests were much higher than with permethrin treated netting over the same 100-500 mg/m(2) dosage range. Chlorfenapyr has potential for malaria control in treated-net or residual spraying applications in areas where mosquitoes are pyrethroid resistant. For treated-net applications chlorfenapyr might be combined with pyrethroid as a mixture to provide personal protection as well as to give control of resistant mosquitoes.

Multiple insecticide resistance mechanisms in Anopheles gambiae and Culex quinquefasciatus from Benin, West Africa.

Because free-insecticide treated net distribution is planned in Benin (West Africa) during the next few years, we investigated the type, frequency and distribution of insecticide resistance mechanisms in Anopheles gambiae and Culex quinquefasciatus mosquitoes in four localities selected on the basis of contrasting agricultural practices, use of insecticides and environment. Bioassays with WHO diagnostic test kits were carried out using pyrethroid, carbamate, organophosphate and organochlorine insecticides. An. gambiae mosquitoes were identified to species and to M or S molecular forms using PCR techniques. Molecular and biochemical assays were carried out to identify kdr and Ace.1 mutations in individual mosquitoes and to detect any increase in the activity of enzymes typically involved in insecticide metabolism (oxidase, esterase and glutathion-S-transférases). WHO diagnostic tests showed high frequency of resistance in An. gambiae and Cx. quinquefasciatus to permethrin and DDT in three areas. This was consistent with the presence of target site insensitivity due to kdr mutation and to increased metabolism through enzymatic activity. Kdr was expressed in both M and S forms. However, less than 1% of An. gambiae or Cx. quiqnuefasciatus showed the presence of the Ace.1(R) mutation. Carbamate/OP resistance was present at higher frequency in Culex than in An. gambiae. Dieldrin resistance was present in both species at all four localities. A higher frequency of pyrethroid-resistance was found in An. gambiae mosquitoes collected in urban areas compared to those collected in rice growing areas. The expansion of vegetable growing within urban areas probably contributed to selection pressure on mosquitoes. The detection of multiple resistance mechanisms in both An. gambiae and Cx. quinquefasciatus in Benin may represent a threat for the efficacy of ITNs and other forms of vector control such as indoor residual spraying in the future.

The indoor use of plastic sheeting pre-impregnated with insecticide for control of malaria vectors.

OBJECTIVE: To evaluate the efficacy of permethrin-treated plastic sheeting (ITPS) applied as a lining to the ceiling or walls of rooms against pyrethroid-susceptible and pyrethroid-resistant Anopheles gambiae. METHOD: Overnight tests were carried out in veranda-trap experimental huts in Vallée du Kou, where two molecular forms of A. gambiae, S and M, occur. The S form is mostly pyrethroid resistant due to the kdr mechanism, and the M form is mostly kdr susceptible. A variety of ITPS covered surfaces were tested, ranging from ceiling only to all walls plus ceiling covered. RESULTS: ITPS had a major effect on the mortality of mosquitoes, the proportion killed being dependent upon the surface area covered. Homozygotes for kdr resistance showed lower rates of mortality than did heterozygotes or homozygotes for susceptibility. Deterred entry of mosquitoes and inhibition of blood feeding were also correlated with surface area covered. The mode of action and efficacy of ITPS seems to bear closer resemblance to that induced by indoor residual spraying (IRS) than to that induced by insecticide-treated nets. CONCLUSIONS: ITPS might be conceived as being equivalent to long-lasting or permanent IRS but without some of the operational constraints normally associated with spraying. High coverage of ITPS could potentially have a mass population effect on mosquitoes and give rise to long-term community protection against malaria. A phase III trial is justified to assess the acceptability of ITPS and its efficacy against malaria.

Efficacy of permethrin-treated uniforms in combination with DEET topical repellent for protection of French military troops in Côte d'Ivoire.

In 2000, 22,000 French military personnel were deployed overseas. The French military health service implemented a vector control strategy including personal protection by the use of permethrin preimpregnated battlefield uniforms (BFUs) and the application on the skin of a topical repellent (50% DEET). In 2000, French forces used an industrial process to impregnate cloth with permethrin by soaking it before cut-out of the BFU. A study was implemented in four experimental huts in Côte d'Ivoire to assess the field efficacy of the impregnated BFUs and their resistance to washing. Taking into account the systematic variations in each variable in the field and using a modeling based on logistic regression and discriminant analysis, this study showed that after 6 h without reapplication, the protective effects of the use of DEET as skin repellent was not significant, perhaps due to the high density of Anopheles mosquitoes during the night catching sessions and an average time of effective repellency of < 2 or 3 h in the field. The analysis also showed that the French process of industrial impregnation of permethrin of the BFU offered in 2000 some protection from mosquito bites but not enough to reduce significantly the incidence of malaria among nonimmune troops. No positive or negative interaction was noted when DEET and the impregnated BFUs were used together.

Experimental hut comparisons of nets treated with carbamate or pyrethroid insecticides, washed or unwashed, against pyrethroid-resistant mosquitoes.

The efficacy against mosquitoes (Diptera: Culicidae) of a bednet treated with carbamate insecticide [carbosulfan capsule suspension (CS) 200 mg/m(2)] was compared with four types of pyrethroid-treated nets in veranda-trap huts at Yaokoffikro near Bouaké, Côte d'Ivoire, where the malaria vector Anopheles gambiae Giles carries the kdr gene (conferring pyrethroid resistance) at high frequency and Culex quinquefasciatus Say is also pyrethroid resistant. Pyrethroids compared were lambdacyhalothrin CS 18 mg/m(2), alphacypermethrin water dispersible granules (WG) 20 mg/m(2), deltamethrin 50 mg/m(2) (Permanet) and permethrin emulsifiable concentrate (EC) 500 mg/m(2). Insecticidal power and personal protection from mosquito bites were assessed before and after the nets were used for 8 months and hand washed five times in cold soapy water. Before washing, all treatments except permethrin significantly reduced blood-feeding and all had significant insecticidal activity against An. gambiae. The carbosulfan net gave significantly higher killing of An. gambiae than all pyrethroid treatments except the Permanet. Against Culex spp., carbosulfan was more insecticidal and gave a significantly better protective effect than any of the pyrethroid treatments. After washing, treated nets retained various degrees of efficacy against both mosquito genera - but least for the carbosulfan net. Washed nets with three types of pyrethroid treatment (alphacypermethrin, lambdacyhalothrin, permethrin) gave significantly higher mortality rates of Culex than in huts with the same pyrethroid-treated nets before washing. After five washes, the Permanet, which is sold as a long-lasting insecticidal product, performed no better than the other nets in our experimental conditions.

Resistance to carbosulfan in Anopheles gambiae from Ivory Coast, based on reduced sensitivity of acetylcholinesterase.

Resistance to carbosulfan, a carbamate insecticide, was detected in field populations of the malaria vector mosquito Anopheles gambiae Giles (Diptera: Culicidae) from two ecologically contrasted localities near Bouaké, Ivory Coast: rural M'bé with predominantly M form of An. gambiae susceptible to pyrethroids; suburban Yaokoffikro with predominantly S form of An. gambiae highly resistant to pyrethroids (96% kdr). The discriminating concentration of 0.4% carbosulfan (i.e. double the LC100) was determined from bioassays with the susceptible An. gambiae Kisumu strain. Following exposure to the diagnostic dosage (0.4% carbosulfan for 1 h), mortality rates of female An. gambiae adults (reared from larvae collected from ricefields) were 62% and 29% of those from M'bé and Yaokoffikro, respectively, 24 h post-exposure. Exposure for 3 min to netting impregnated with the operational dosage of carbosulfan 200 mg/m2 gave mortality rates of 88% of those from M'bé and only 12.2% for Yaokoffikro. In each case the control untreated mortality rate was insignificant. Biochemical assays to detect possible resistance mechanism(s) revealed the presence of insensitive AChE in populations of An. gambiae at both localities, more prevalent in the S form at Yaokoffikro than in M form at M'bé, as expected from bioassays results. Our study demonstrates the need to monitor carbamate resistance among populations of the An. gambiae complex in Africa, to determine its spread and anticipate vector control failure if these insecticides are employed.

Efficacy of mosquito nets treated with insecticide mixtures or mosaics against insecticide resistant Anopheles gambiae and Culex quinquefasciatus (Diptera: Culicidae) in Côte d'Ivoire.

Only pyrethroid insecticides have so far been recommended for the treatment of mosquito nets for malaria control. Increasing resistance of malaria vectors to pyrethroids threatens to reduce the potency of this important method of vector control. Among the strategies proposed for resistance management is to use a pyrethroid and a non-pyrethroid insecticide in combination on the same mosquito net, either separately or as a mixture. Mixtures are particularly promising if there is potentiation between the two insecticides as this would make it possible to lower the dosage of each, as has been demonstrated under laboratory conditions for a mixture of bifenthrin (pyrethroid) and carbosulfan (carbamate). The effect of these types of treatment were compared in experimental huts on wild populations of Anopheles gambiae Giles and the nuisance mosquito Culex quinquefasciatus Say, both of which are multi-resistant. Four treatments were evaluated in experimental huts over six months: the recommended dosage of 50 mg m(-2) bifenthrin, 300 mg m(-2) carbosulfan, a mosaic of 300 mg m(-2) carbosulfan on the ceiling and 50 mg m(-2) bifenthrin on the sides, and a mixture of 6.25 mg m(-2) carbosulfan and 25 mg m(-2) bifenthrin. The mixture and mosaic treatments did not differ significantly in effectiveness from carbosulfan and bifenthrin alone against anophelines in terms of deterrency, induced exophily, blood feeding inhibition and overall mortality, but were more effective than in earlier tests with deltamethrin. These results are considered encouraging, as the combination of different classes of insecticides might be a potential tool for resistance management. The mixture might have an advantage in terms of lower cost and toxicity.