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 degrees 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

In silico identification of a candidate synthetic peptide (Tsgf1(18-43)) to monitor human exposure to tsetse flies in West Africa

Background: The analysis of humoral responses directed against the saliva of blood-sucking arthropods was shown to provide epidemiological biomarkers of human exposure to vector-borne diseases. However, the use of whole saliva as antigen presents several limitations such as problems of mass production, reproducibility and specificity. The aim of this study was to design a specific biomarker of exposure to tsetse flies based on the in silico analysis of three Glossina salivary proteins (Ada, Ag5 and Tsgf1) previously shown to be specifically recognized by plasma from exposed individuals. Methodology/Principal Findings: Synthetic peptides were designed by combining several linear epitope prediction methods and Blast analysis. The most specific peptides were then tested by indirect ELISA on a bank of 160 plasma samples from tsetse infested areas and tsetse free areas. Anti-Tsgf1(18-43) specific IgG levels were low in all three control populations (from rural Africa, urban Africa and Europe) and were significantly higher (p < 0.0001) in the two populations exposed to tsetse flies (Guinean HAT foci, and South West Burkina Faso). A positive correlation was also found between Anti-Tsgf1(18-43) IgG levels and the risk of being infected by Trypanosoma brucei gambiense in the sleeping sickness foci of Guinea. Conclusion/Significance: The Tsgf1(18-43) peptide is a suitable and promising candidate to develop a standardize immunoassay allowing large scale monitoring of human exposure to tsetse flies in West Africa. This could provide a new surveillance indicator for tsetse control interventions by HAT control programs

Human IgG antibody response to Aedes aegypti Nterm-34 kDa salivary peptide as an indicator to identify areas at high risk for dengue transmission : a retrospective study in urban settings of Vientiane city, Lao PDR

ObjectiveUsing human IgG antibody response to the Aedes Nterm-34kDa salivary peptide as an indicator of human exposure to Aedes bites in surveying exposed populations from areas at risk of dengue virus (DENV) transmission in urban settings of Vientiane city, Lao PDR. MethodsEnzyme-linked immunosorbent assay tests were performed to measure the IgG response to Nterm-34kDa peptide in blood samples collected within a flavivirus seroprevalence survey carried out in 2006 including 3558 randomly selected individuals. The level of IgG response to the Nterm-34kDa peptide in individuals was analysed in relation to the level of urbanisation of the individual's residence, areas that presented significant differences in the prevalence of recent DENV infection. ResultsNo differences were observed in the anti-Nterm-34kDa IgG level between DENV-positive and DENV-negative individuals. However, the level of specific IgG response was higher among individuals living in slightly urbanised neighbourhoods than among those in more highly urbanised areas (P<0.0001). Interestingly, a similar pattern had already been observed concerning the prevalence of recent DENV infection in the same populations. ConclusionThe results of this retrospective study indicate that the evaluation of human IgG response to the Aedes Nterm-34kDa salivary peptide could be a useful indicator to identify places with risk of dengue virus transmission in urban endemic areas. ObjectifUtiliser la reponse de l'anticorps IgG humaine au peptide salivaire Nterm-34kDa de l'Aedes comme un indicateur de l'exposition humaine aux piqures de l'Aedes dans la surveillance des populations exposees dans les zones a risque de transmission du virus de la dengue (DENV) en milieu urbain de la ville de Vientiane, au Laos. MethodesDes tests ELISA ont ete effectues pour mesurer la reponse IgG au peptide Nterm-34kDa dans des echantillons de sang preleves dans une etude de seroprevalence du flavivirus realisee en 2006, sur 3558 personnes choisies aleatoirement. Le niveau de reponse IgG contre le peptide Nterm-34kDa chez les individus a ete analyse en relation avec le niveau d'urbanisation du lieu de residence des individus, les zones qui presentaient des differences significatives dans la prevalence de l'infection DENV recente. ResultatsAucune difference n'a ete observee dans le niveau d'IgG anti-Nterm-34kDa entre les individus positifs et negatifs pour le DENV. Cependant, le niveau de la reponse IgG specifique etait plus eleve chez les personnes vivant dans des quartiers un peu urbanises que chez ceux vivant dans des zones plus fortement urbanisees (P<0,0001). De facon interessante, une tendance similaire avait deja ete observee dans la prevalence de l'infection DENV recente dans les memes populations. ConclusionLes resultats de cette etude retrospective indiquent que l'evaluation de la reponse IgG humaine au peptide salivaire Nterm-34kDa d'Aedes pourrait etre un indicateur utile pour identifier les zones a risque de transmission du virus de la dengue dans les zones endemiques urbaines. ObjetivoUtilizando la respuesta de anticuerpos IgG humanos al peptido salivar Nterm-34kDa de Aedes como un indicador de la exposicion humana a picaduras de Aedes, estudiar las poblaciones expuestas pertenecientes a areas en riesgo de transmision del virus del dengue (VDEN) en zonas urbanas de la ciudad de Vientiane, Laos. MetodosSe realizaron pruebas de ELISA para medir la respuesta de IgG al peptido Nterm-34kDa en muestras de sangre recogidas como parte de un estudio de seroprevalencia de flavivirus llevado a cabo en el 2006, incluyendose 3558 individuos escogidos al azar. Se analizo el nivel de respuesta de IgG al peptido Nterm-34kDa con relacion al nivel de urbanizacion de la residencia del individuo, areas que presentaron diferencias significativas en la prevalencia de infecciones recientes por VDEN. ResultadosNo se observaron diferencias entre el nivel de IgG anti-Nterm-34kDa entre individuos positivos y negativos para VDEN. Sin embargo, el nivel de respuesta IgG especifica era mayor entre individuos viviend