Durability of the deltamethrin-treated polypropylene long-lasting net LifeNet® in a pyrethroid resistance area in south western Benin: A phase III trial.

BACKGROUND: Long-lasting insecticidal bed nets (LLINs) are a key measure for preventing malaria and their evaluation is coordinated by the World Health Organization Pesticide Evaluation Scheme (WHOPES). LifeNet® was granted WHOPES time-limited interim recommendation in 2011 after successful Phase I and Phase II evaluations. Here, we evaluated the durability and community acceptance of LifeNet® in a Phase III trial from June 2014 to June 2017 in Benin rural area. METHODS: A prospective longitudinal, cluster-randomized, controlled trial with households as the unit of observation was designed to assess the performance of LifeNet® over a three-year period, using a WHOPES fully recommended LLIN (PermaNet® 2.0) as a positive control. The primary outcomes were the bioassay performance using WHO cone assays and tunnel tests, the insecticide content and physical integrity. RESULTS: At baseline, 100% of LLINs were within the tolerance limits of their target deltamethrin concentrations. By 36 months only 17.3% of LifeNet® and 8.5% of PermaNet® LLINs still were within their target deltamethrin concentrations. Despite these low rates, 100% of both LLINs meet WHO efficacy criteria (≥ 80% mortality or ≥ 95% knockdown or tunnel test criteria of ≥ 80% mortality or ≥ 90% blood-feeding inhibition) after 36 months using WHO cone bio-assays and tunnel tests. The proportion of LLINs in good physical condition was 33% for LifeNet® and 29% for PermaNet® after 36 months. After 36 M the survivorship was 21% and 26% for LifeNet® and PermaNet® respectively. Although both LLINs were well accepted by the population, complaints of side effects were significantly higher among LifeNet® users than PermaNet® ones. CONCLUSION: LifeNet® LLINs did meet WHO criteria for bio-efficacy throughout the study period and were well accepted by the population. This is an important step towards getting a full WHO recommendation for use in malaria endemic countries.

Diagnostic capabilities of self-reported psychoactive substance use among patients admitted to psychiatric consultations in Benin, West Africa.

BACKGROUND: There is a high prevalence of psychoactive substance use among patients with mental health disorders. The optimal treatment of patients with mental health disorders requires an awareness of their history pertaining substance use. Several methods are used to assess the use of substance. Each of them embodies its limitations. This study aimed at assessing the diagnostic capability of a self-report psychoactive substance use among patients at the National Psychiatric University Hospital of Cotonou, Benin. METHODS: A cross-sectional survey was conducted from August 1, 2021 to November 24, 2021. A total of 157 consenting patients admitted to psychiatric consultations were successively enrolled in the ongoing study. They were screened for the use of psychoactive substance with Alcohol, Smoking and Substance Involvement Screening Test (ASSIST), followed by urine test using the NarcoCheck® kit for qualitative detection of substances or its metabolites. To assess the diagnostic capability, the participants' self-responses were compared with their urine test results. The sensitivity, specificity, positive and negative predictive values, and kappa coefficient were also calculated. RESULTS: The frequency of lifetime psychoactive substance use according to self-report was 81.5% (95% CI: 0.746-0.873), while over the past three months (recent use) was 52.2% (95% CI: 0.441-0.603) and 58.6% based on the urine test. Alcohol, tobacco and cannabis were the most prevalent psychoactive substance used. The overall concordance between self-reported psychoactive substance use and the urine test (gold standard) was moderate (sensitivity = 66%; kappa = 0.46). Self-report cocaine use compared with urine test showed the highest concordance (sensitivity = 100%; kappa = 79%), followed by tobacco (sensitivity = 58%, kappa = 41%). On an average 70% of urine test results were consistent with self-report (VPP). Participants' were more accurate when they were reporting no psychoactive substance use as suggested by the high negative predictive value (NPV). CONCLUSION: Diagnostic capability of self-reporting of psychoactive substance use among patients admitted to psychiatric consultations was moderate. Therefore self-reporting may not estimate the exact prevalence of psychoactive substance use. Optimal identification of psychoactive substances use in psychiatric patients requires both history and urine testing. The integration of these two approaches is an excellent method to find out the level, frequency and nature of drug used.

Prevalence, associated factors and level of dependence of substance use among urban secondary school students, Benin.

The use of psychoactive substances is constantly increasing, particularly among young people. This study aimed to estimate the prevalence, associated factors and the level of dependence of those substances among secondary school students in Benin. This cross-sectional study included 627 students in grades 8-12, selected using a multi-stage sampling technique. Data were collected using the ASSIST questionnaire, followed by urine screening. Logistic regression analysis was performed to estimate factors associated with substance use. Overall, the lifetime prevalence of psychoactive substance use was 95.4% (95% CI = 93.4-96.9), while the current use was 78.8% (95% CI = 75.3-81.9). The most commonly used substances in the past 3 months were alcohol, followed by stimulants and tobacco; 221 samples were analysed. Twenty-two (9.95%) were positive by urine screening. Substances detected were tramadol, fentanyl, THC, K2, BZDs, alcohol, methamphetamine and cotinine. Of the current users, 2.27% (n = 11) were at high risk of dependency. An association was found between substance use and age (p = 0.02). In conclusion, this study came up with a high prevalence of substance use among students. There is a need to develop and implement a health education programme in secondary schools to raise awareness of the potential risks.

Nonmedical use of tramadol among secondary school students in Benin, Africa.

Background: Nonmedical use of tramadol among the young Beninese population is an increasing public health concern. However, there is little research on tramadol use in West Africa.Objectives: This study aimed to assess the prevalence, factors associated with nonmedical use of tramadol and to determine the level of therapeutic intervention needed.Methods: A cross-sectional study design and multi-stage sampling method was used among 384 secondary school students, within the age group of 10-24 years old who gave their consent/assent. An interviewer-administered modified questionnaire based on ASSIST was administered. Urinary toxicological test was performed using NarcoCheck® quick for qualitative detection of tramadol or its metabolites. Logistic regression analysis was performed to identify factors associated with nonmedical use of tramadol.Results: The average age of our respondents was 17 ± 2 SD years old; 58.3% were males and 41.7% females. The lifetime prevalence of nonmedical use of tramadol was 9.6% (95% CI: 6.7-12.6) (13.4% males and 4.4% females) and the average age at onset was 14.8 ± 1.8 years old. Only 1.4% (n = 4) were using tramadol as shown by urine screen. Among users, 45.9% reported a hazardous level of use and required a brief intervention. In a multivariate logistic regression model, tobacco (P < .001), cannabis (p = .023) and amphetamine (p = .037) were significantly associated with nonmedical use of tramadol. The most prevalent motives for nonmedical use of tramadol was experimentation (45.9%) and the leading source for obtaining tramadol was street-level markets (86.5%).Conclusion: These results indicate that nonmedical use of tramadol affects young in Benin and represent a considerable concern among secondary school students.

Poor maternal anthropometric characteristics and newborns' birth weight and length: a cross-sectional study in Benin.

Background: Maternal undernutrition is known to negatively impact newborns' birth weight and length, but this finding is poorly documented in the Beninese population. This study aimed to assess the effect of maternal anthropometry on mean birth weight and length in a Beninese cohort of newborns. Methods: A cross-sectional study was carried out in Tori Bossito, Republic of Benin. Pregnant women attending maternity wards between June 2007 and July 2008 were recruited. At delivery the women's characteristics, including weight and height, were gathered and newborns' birth weights and lengths were measured. Statistical analysis was performed using multiple linear regression. Results: A total of 526 mother-infant pairs were enrolled; 29.8% of women had low weight status and 26.2% had short stature (<155 cm). The mean birth weight was 2985 g (standard deviation [SD] 384) the mean birth length was 48.7 cm (SD 2.2). Maternal low weight status (coefficient=-151.81, p<0.001) and short stature (coefficient=-135.49, p<0.001) reduced the mean birth weight. Similar results were found for mean birth length, which was decreased by maternal low weight status (coefficient=-0.42, p=0.04) and short stature (coefficient=-0.51, p=0.01). Conclusion: Maternal undernutrition expressed by low anthropometry remains problematic in the Beninese population and induces transmission of malnutrition. Nutritional interventions are required to break this vicious cycle.

Prévalence et description des pratiques d'allaitement maternel exclusif dans une zone semi-rurale au sud du Bénin

Introduction : Dans un contexte de non atteinte des recommandations de l'OMS et de l'UNICEF con-cernant l'allaitement maternel exclusif, cette étude avait pour objectif de décrire les pratiques et habi-tudes d'allaitement maternel dans une population semi-rurale au sud du Bénin. Matériel et méthode : Cette enquête s'est déroulée à Sèmè-Kpodji située à 15 km au sud-est de la capitale Porto-Novo. Les pratiques d'allaitement maternel exclusif de 0 à 6 mois ont été observées et notées chez 339 femmes ayant accouché entre janvier 2015 et janvier 2016. Résultats : La plupart des enfants (71,40%) ont été mis au sein dès la première de vie ; l'âge moyen de sevrage était de 4,5 mois. Le taux d'allaitement maternel exclusif était de 53,9% et a diminué pro-gressivement en fonction de l'âge de l'enfant. Les taux d'allaitement maternel prédominant et complété ont varié de 25,4% à 49,6% et de 0 à 40,7% respectivement. La durée moyenne des tétées est passée de 24,1 à 15,1 minutes et la fréquence des repas de 9,5 à 6,4 repas par jour. Conclusion : Cette enquête confirme la nécessité de continuer les interventions de santé publique visant à promouvoir l'allaitement maternel exclusif afin d'améliorer les indicateurs de santé materno-infantile

Operational Assessment of Long-Lasting Insecticidal Nets by Using an Anopheles Salivary Biomarker of Human-Vector Contact.

The widespread implementation of long-lasting insecticidal nets (LLINs) is a major intervention method for malaria control. Although the LLINs coverage increases, information available on the physical integrity (PI) of implemented LLINs is incomplete. This study aimed to validate human IgG antibody (Ab) response to Anopheles gSG6-P1 salivary peptide antigen, previously demonstrated as a pertinent biomarker of human exposure to Anopheles bites, for evaluating the PI of LLINs in field conditions. We analyzed data from 262 randomly selected children (< 5 years of age) in health districts of Benin. Anti-gSG6-P1 IgG responses were assessed and compared with the PI of LLINs that these same children slept under, and evaluated by the hole index (HI). Specific IgG levels were positively correlated to LLINs HI (r = 0.342; P < 0.0001). According to antipeptide IgG level (i.e., intensity of vector exposure), two categories of LLINs PI were defined: 1) group "HI: [0, 100]" corresponding to LLINs with "good" PI and 2) "HI > 100" corresponding to LLINs with "bad" PI. These results suggest that human Ab response to salivary peptide could be a complementary tool to help defining a standardized threshold of efficacy for LLINs under field use.

Lack of artemisinin resistance in Plasmodium falciparum in northwest Benin after 10 years of use of artemisinin-based combination therapy.

AIM: In Benin, artemisinin-based combination therapy (ACT) has been recommended as the first-line treatment for uncomplicated Plasmodium falciparum malaria since 2004. The emergence in Southeast Asia of parasites that are resistant to artemisinins poses a serious threat to global control of this disease. The presence of artemisinin resistance genotypes in parasite populations in Benin is currently unknown. The present study investigated the prevalence of relevant K13-propeller gene polymorphisms in parasite isolates from the north-western region of Benin. METHOD: Plasmodium falciparum isolates were collected from children with a confirmed diagnosis of malaria aged 6 months to 5 years in two towns, Cobly and Djougou, in the north-western part of Benin. The study was conducted during the rainy season from July to November 2014 in local health facilities. The K13-propeller gene was amplified in parasite isolates using nested PCR and subsequently sequenced. RESULTS: A total of 108 children were recruited into the study. The efficiency of amplification reactions was 72% (78/108). The propeller domain of the K13 gene was successfully sequenced in 78 P. falciparum isolates; all of them were wild type with no polymorphisms detectable. CONCLUSION: The absence of mutations in the K13 gene indicates that P. falciparum parasite populations in the study area are still fully susceptible to artemisinins.

Effectiveness of insecticidal nets on uncomplicated clinical malaria: a case-control study for operational evaluation.

BACKGROUND: In a context of large-scale implementation of malaria vector control tools, such as the distribution of long-lasting insecticide nets (LLIN), it is necessary to regularly assess whether strategies are progressing as expected and then evaluate their effectiveness. The present study used the case-control approach to evaluate the effectiveness of LLIN 42 months after national wide distribution. This study design offers an alternative to cohort study and randomized control trial as it permits to avoid many ethical issues inherent to them. METHODS: From April to August 2011, a case-control study was conducted in two health districts in Benin; Ouidah-Kpomasse-Tori (OKT) in the south and Djougou-Copargo-Ouake (DCO) in the north. Children aged 0-60 months randomly selected from community were included. Cases were children with a high axillary temperature (≥37.5 °C) or a reported history of fever during the last 48 h with a positive rapid diagnostic test (RDT). Controls were children with neither fever nor signs suggesting malaria with a negative RDT. The necessary sample size was at least 396 cases and 1188 controls from each site. The main exposure variable was "sleeping every night under an LLIN for the 2 weeks before the survey" (SL). The protective effectiveness (PE) of LLIN was calculated as PE = 1 - odds ratio. RESULTS: The declared SL range was low, with 17.0 and 27.5 % in cases and controls in the OKT area, and 44.9 and 56.5 % in cases and controls, in the DCO area, respectively. The declared SL conferred 40.5 % (95 % CI 22.2-54.5 %) and 55.5 % (95 % CI 28.2-72.4 %) protection against uncomplicated malaria in the OKT and the DCO areas, respectively. Significant differences in PE were observed according to the mother's education level. CONCLUSION: In the context of a mass distribution of LLIN, their use still conferred protection in up to 55 % against the occurrence of clinical malaria cases in children. Social factors, the poor use and the poor condition of an LLIN can be in disfavour with its effectiveness. In areas, where LLIN coverage is assumed to be universal or targeted at high-risk populations, case-control studies should be regularly conducted to monitor the effectiveness of LLIN. The findings will help National Malaria Control Programme and their partners to improve the quality of malaria control according to the particularity of each area or region as far as possible.

Therapeutic efficacy of artemether-lumefantrine for the treatment of uncomplicated falciparum malaria in northwest Benin.

BACKGROUND: Artemether/lumefantrine (Coartem(®)) has been used as a treatment for uncomplicated Plasmodium falciparum infection since 2004 in Benin. This open-label, non-randomized study evaluated efficacy of artemether-lumefantrine (AL) in treatment of uncomplicated falciparum malaria in children aged 6-59 months in two malaria transmission sites in northwest Benin. METHODS: A 42-day therapeutic efficacy study was conducted between August and November 2014, in accordance with 2009 WHO guidelines. One-hundred and twenty-three children, aged 6 months to 5 years, with uncomplicated falciparum malaria were recruited into the study. The primary endpoint was parasitological cure on day 28 and day 42 while the secondary endpoints included: parasite and fever clearance, improvement in haemoglobin levels. Outcomes were classified as early treatment failure (ETF), late clinical failure, late parasitological failure, and adequate clinical and parasitological response (ACPR). RESULTS: Before PCR correction, ACPR rates were 87% (95 % CI 76.0-94.7) and 75.6%, respectively (95% CI 67.0-82.9) on day 28 and day 42. In each study site, ACPR rates were 78.3% in Djougou and 73% in Cobly on day 42. There was no ETF and after PCR correction ACPR was 100% in study population. All treatment failures were shown to be due to new infections. Fever was significantly cleared in 24 h and approximately 90% of parasites where cleared on day 1 and almost all parasites were cleared on day 2. Haemoglobin concentration showed a slight increase with parasitic clearance. CONCLUSION: AL remains an efficacious drug for the treatment of uncomplicated falciparum malaria in Benin, although higher rates of re-infection remain a concern. Surveillance needs to be continued to detect future changes in parasite sensitivity to artemisinin-based combination therapy.

Human exposure to early morning Anopheles funestus biting behavior and personal protection provided by long-lasting insecticidal nets.

A shift towards early morning biting behavior of the major malaria vector Anopheles funestus have been observed in two villages in south Benin following distribution of long-lasting insecticidal nets (LLINs), but the impact of these changes on the personal protection efficacy of LLINs was not evaluated. Data from human and An. funestus behavioral surveys were used to measure the human exposure to An. funestus bites through previously described mathematical models. We estimated the personal protection efficacy provided by LLINs and the proportions of exposure to bite occurring indoors and/or in the early morning. Average personal protection provided by using of LLIN was high (≥80% of the total exposure to bite), but for LLIN users, a large part of remaining exposure occurred outdoors (45.1% in Tokoli-V and 68.7% in Lokohoué) and/or in the early morning (38.5% in Tokoli-V and 69.4% in Lokohoué). This study highlights the crucial role of LLIN use and the possible need to develop new vector control strategies targeting malaria vectors with outdoor and early morning biting behavior. This multidisciplinary approach that supplements entomology with social science and mathematical modeling illustrates just how important it is to assess where and when humans are actually exposed to malaria vectors before vector control program managers, policy-makers and funders conclude what entomological observations imply.

Reports of long-lasting insecticidal bed nets catching on fire: a threat to bed net users and to successful malaria control?

BACKGROUND: One of the control tools to reduce malaria transmission is the use of LLINs. However, several studies show that household bed net use is quite low. A study was developed to better understand the cultural factors that might explain these gaps in Benin. One reason mentioned is that bed nets can catch on fire and cause harm. This paper presents a summary of these findings, their analysis and the ensuing issues. METHODS: This anthropological study is based on an inductive qualitative approach, including 91 semi-structured interviews conducted from July 2011 to March 2012 in a health district in Southern Benin. RESULTS: Fifty-six persons stated that bed nets can catch on fire but do not always refer to specific facts. However, 34 of the 56 people narrate specific events they heard or experienced. 39 accounts were geographically located and situated in time, with various details. In 27 situations, people were burned, for which 12 people reportedly died. DISCUSSION: The disparity between these results and the dearth of bibliographic documentation in the initial search prompted a more in-depth literature review: 16 contributions between 1994 and 2013 were found. Bed net fires were noted in 10 countries, but it is impossible to ascertain the frequency of such events. Moreover, bodily harm can be significant, and several cases of death attributed to bed net fires were noted. CONCLUSIONS: Indisputably, the use of bed nets to reduce the impact of this terrible disease is an optimal control method. However, the perception that LLINs have a potentially negative effect hinders the use rate in the real world, at least for some. If some people fear the risk of fires, this possibility must be addressed during information and prevention sessions on malaria, with a communication strategy tailored to specific social contexts. Moreover, all possible measures should be taken to limit the harm suffered by individuals and their families.

The residual life of bendiocarb on different substrates under laboratory and field conditions in Benin, Western Africa.

BACKGROUND: The efficacy of bendiocarb against pyrethroid resistant An. gambiae and the residual life of this insecticide on different substrates were evaluated under laboratory and field conditions. METHODS: Bioassays according to the WHO (World Health Organization) standard protocol were carried out on different substrates impregnated with bendiocarb. Data were analyzed using a binomial regression model with R software. RESULTS: A good efficacy of the bendiocarb against pyrethroid resistant An. gambiae and a high variation of its residual life according to the surfaces treated was observed. The probability that a female mosquito died after exposure to a treated substrate was below 80% after 13 weeks for the teak wood; 7 weeks for the wall made with a mixture of sand and cement and 6 weeks for walls made with red clay and those made with a mixture of the red clay and cement. CONCLUSIONS: Considering the residual life of bendiocarb on walls made with red clay, the main substrates treated during IRS campaigns in rural areas in Benin, more than 2 treatments rounds per year would be necessary to achieve a long term efficacy of IRS using bendiocarb in these areas. Financial and logistical resources required to achieve such levels of coverage need more political will from leaders of African endemic countries. While waiting for innovative malaria control tool, alternative insecticides or combinations of insecticides have to be used for insecticide resistance management in Benin.

First attempt to validate human IgG antibody response to Nterm-34kDa salivary peptide as biomarker for evaluating exposure to Aedes aegypti bites.

BACKGROUND: Much effort is being devoted for developing new indicators to evaluate the human exposure to Aedes mosquito bites and the risk of arbovirus transmission. Human antibody (Ab) responses to mosquito salivary components could represent a promising tool for evaluating the human-vector contact. METHODOLOGY/PRINCIPAL FINDINGS: To develop a specific biomarker of human exposure to Aedes aegypti bites, we measured IgG Ab response to Ae. aegypti Nterm-34 kDa salivary peptide in exposed children in 7 villages of Southern Benin (West Africa). Results showed that specific IgG response presented high inter-individual heterogeneity between villages. IgG response was associated with rainfall and IgG level increased from dry (low exposure) to rainy (high exposure) seasons. These findings indicate that IgG Ab to Nterm-34 kDa salivary peptide may represent a reliable biomarker to detect variation in human exposure to Ae. aegypti bites. CONCLUSION/SIGNIFICANCE: This preliminary study highlights the potential use of Ab response to this salivary peptide for evaluating human exposure to Ae. aegypti. This biomarker could represent a new promising tool for assessing the risk of arbovirus transmission and for evaluating the efficacy of vector control interventions.

Combination of malaria vector control interventions in pyrethroid resistance area in Benin: a cluster randomised controlled trial.

BACKGROUND: Malaria control efforts and elimination in Africa are being challenged by the development of resistance of parasites to antimalarial drugs and vectors to insecticides. We investigated whether the combination of long-lasting insecticidal mosquito nets (LLINs) with indoor residual spraying (IRS) or carbamate-treated plastic sheeting (CTPS) conferred enhanced protection against malaria and better management of pyrethroid-resistance in vectors than did LLINs alone. METHODS: We did a cluster randomised controlled trial in 28 villages in southern Benin, west Africa. Inclusion criteria of the villages were moderate level of pyrethroid resistance in malaria vectors and minimum distance between villages of 2 km. We assessed four malaria vector control interventions: LLIN targeted coverage to pregnant women and children younger than 6 years (TLLIN, reference group), LLIN universal coverage of all sleeping units (ULLIN), TLLIN plus full coverage of carbamate-IRS applied every 8 months (TLLIN+IRS), and ULLIN plus full coverage of CTPS lined up to the upper part of the household walls (ULLIN+CTPS). The interventions were allocated to villages by a block randomisation on the basis of preliminary surveys and children of each village were randomly selected to participate with computer-generated numbers. The primary endpoint was the incidence density rate of Plasmodium falciparum clinical malaria in children younger than 6 years as was analysed by Poisson regression taking into account the effect of age and the sampling design with a generalised estimating equation approach. Clinical and parasitological information were obtained by active case detection of malaria episodes during 12 periods of 6 consecutive days scheduled at six weekly intervals and by cross-sectional surveys of asymptomatic plasmodial infections. Children or study investigators were not masked to study group. This study is registered with Current Controlled Trials, number ISRCTN07404145. FINDINGS: Of 58 villages assessed, 28 were randomly assigned to intervention groups. 413-429 children were followed up in each intervention group for 18 months. The clinical incidence density of malaria was not reduced in the children from the ULLIN group (incidence density rate 0·95, 95% CI 0·67-1·36, p=0·79), nor in those from the TLLIN+IRS group (1·32, 0·90-1·93, p=0·15) or from the ULLIN+CTPS group (1·05, 0·75-1·48, p=0·77) compared with the reference group (TLLIN). The same trend was observed with the prevalence and parasite density of asymptomatic infections (non significant regression coefficients). INTERPRETATION: No significant benefit for reducing malaria morbidity, infection, and transmission was reported when combining LLIN+IRS or LLIN+CTPS compared with a background of LLIN coverage. These findings are important for national malaria control programmes and should help the design of more cost-effective strategies for malaria control and elimination. FUNDING: Ministère Français des Affaires Etrangères et Européennes (FSP project 2006-22), Institut de Recherche pour le Développement, President's Malaria Initiative (PMI) of US Governement.

Dry season determinants of malaria disease and net use in Benin, West Africa.

BACKGROUND: To achieve malaria eradication, control efforts have to be sustained even when the incidence of malaria cases becomes low during the dry season. In this work, malaria incidence and its determinants including bed net use were investigated in children of under 5 years of age in 28 villages in southern Benin during the dry season. METHODS AND FINDINGS: Mean malaria clinical incidence was measured in children aged 0-5 years by active case detection in 28 villages of the Ouidah-Kpomasse-Tori Bossito sanitary district between November 2007 and March 2008. Using Poisson mixed-effect models, malaria incidence was assessed according to the level of transmission by different vector species, and Long-Lasting Insecticide-treated mosquito Nets (LLIN) use and ownership. Then, a Binomial mixed-effect model was developed to assess whether nighttime temperature (derived from MODIS remote sensing data), biting nuisance and LLIN ownership are good predictors of LLIN use >60%. Results suggested that Anopheles funestus (Incidence Rates Ratio (IRR) = 3.38 [IC95 1.91-6]) rather than An. gambiae s.s. is responsible for malaria transmission. A rate of LLIN use >60% was associated with a lower risk of malaria (IRR = 0.6 [IC95 0.37-0.99]). Low nocturnal temperature and high biting nuisance were good predictors of LLIN use >60%. CONCLUSIONS: As recommended by the Malaria Eradication (MalERA) Consultative Group on Modelling, there is a need to understand better the effects of seasonality on malaria morbidity. This study highlights the need to take into account the specificity of malaria epidemiology during the dry-hot season and get a better understanding of the factors that influence malaria incidence and net use. These findings should help National Malaria Control Programmes to implement more effective and sustainable malaria control strategies in Africa.

Malaria infection and disease in an area with pyrethroid-resistant vectors in southern Benin.

BACKGROUND: This study aimed to investigate baseline data on malaria before the evaluation of new vector control strategies in an area of pyrethroid-resistance of vectors. The burden of malaria was estimated in terms of infection (prevalence and parasite density) and of clinical episodes. METHODS: Between December 2007 and December 2008 in the health district of Ouidah-Kpomassè-Tori Bossito (southern Benin), a descriptive epidemiological survey of malaria was conducted. From 28 selected villages, seven were randomized from which a total of 440 children aged 0 to 5 years were randomly selected. Clinical and parasitological information was obtained by active case detection of malaria episodes carried out during eight periods of six consecutive days scheduled at six weekly intervals and by cross-sectional surveys of asymptomatic infection. Entomological information was also collected. The ownership, the use and the correct use of long-lasting insecticide-treated nets (LLINs) were checked over weekly-survey by unannounced visits at home in the late evening. RESULTS: Mean parasite density in asymptomatic children was 586 P. falciparum asexual forms per µL of blood (95%CI 504-680). Pyrogenic parasite cut-off was estimated 2,000 P. falciparum asexual blood forms per µL. The clinical incidence of malaria was 1.5 episodes per child per year (95%CI 1.2-1.9). Parasitological and clinical variables did not vary with season. Anopheles gambiae s.l. was the principal vector closely followed by Anopheles funestus. Entomological inoculation rate was 5.3 (95%CI 1.1-25.9) infective bites per human per year. Frequency of the L1014F kdr (West) allele was around 50%. Annual prevalence rate of Plasmodium falciparum asymptomatic infection was 21.8% (95%CI 19.1-24.4) and increased according to age. Mean rates of ownership and use of LLINs were 92% and 70% respectively. The only correct use of LLINs (63%) conferred 26% individual protection against only infection (OR = 0.74 (95%IC 0.62-0.87), p = 0.005). CONCLUSION: The health district of Ouidah-Kpomassè-Tori Bossito is a mesoendemic area with a moderate level of pyrethroid-resistance of vectors. The used LLINs rate was high and only the correct use of LLINs was found to reduce malaria infection without influencing malaria morbidity.