IgG responses to the gSG6-P1 salivary peptide for evaluating human exposure to Anopheles bites in urban areas of Dakar region, Sénégal

<p>Abstract</p> <p>Background</p> <p>Urban malaria can be a serious public health problem in Africa. Human-landing catches of mosquitoes, a standard entomological method to assess human exposure to malaria vector bites, can lack sensitivity in areas where exposure is low. A simple and highly sensitive tool could be a complementary indicator for evaluating malaria exposure in such epidemiological contexts. The human antibody response to the specific <it>Anopheles </it>gSG6-P1 salivary peptide have been described as an adequate tool biomarker for a reliable assessment of human exposure level to <it>Anopheles </it>bites. The aim of this study was to use this biomarker to evaluate the human exposure to <it>Anopheles </it>mosquito bites in urban settings of Dakar (Senegal), one of the largest cities in West Africa, where <it>Anopheles </it>biting rates and malaria transmission are supposed to be low.</p> <p>Methods</p> <p>One cross-sectional study concerning 1,010 (505 households) children (n = 505) and adults (n = 505) living in 16 districts of downtown Dakar and its suburbs was performed from October to December 2008. The IgG responses to gSG6-P1 peptide have been assessed and compared to entomological data obtained in or near the same district.</p> <p>Results</p> <p>Considerable individual variations in anti-gSG6-P1 IgG levels were observed between and within districts. In spite of this individual heterogeneity, the median level of specific IgG and the percentage of immune responders differed significantly between districts. A positive and significant association was observed between the exposure levels to <it>Anopheles gambiae </it>bites, estimated by classical entomological methods, and the median IgG levels or the percentage of immune responders measuring the contact between human populations and <it>Anopheles </it>mosquitoes. Interestingly, immunological parameters seemed to better discriminate the exposure level to <it>Anopheles </it>bites between different exposure groups of districts.</p> <p>Conclusions</p> <p>Specific human IgG responses to gSG6-P1 peptide biomarker represent, at the population and individual levels, a credible new alternative tool to assess accurately the heterogeneity of exposure level to <it>Anopheles </it>bites and malaria risk in low urban transmission areas. The development of such biomarker tool would be particularly relevant for mapping and monitoring malaria risk and for measuring the efficiency of vector control strategies in these specific settings.</p

The influence of a shrub-based intercropping system on the soil nematofauna when growing millet in Senegal

Woody shrubs commonly co-exist with annual food crops in farmers' fields throughout the Sahel. Management strategies that deliberately include the native shrub Piliostigma reticulatum in Senegalese cropping systems result in soil functioning enhancement that benefits to the associated cereal. The objective of this work was to evaluate shrub effect on soil nematode communities. Soil samples were collected from an experimental design where pearl millet (Pennisetum glaucum) was cultivated alone or with P. reticulatum stands and mulch. Soil nematofauna characteristics were determined and compared with results from soil under pure shrub stands and from bare soil. The analysis of soil nematofauna, characterized by the abundance of different trophic groups and related indices (MI, maturity index; El and SI, enrichment and structure indices), allowed discrimination between treatments with or without shrub presence. The soil nematode community in millet cultivation was dominated by plant feeding nematodes, mainly from the Hoplolaimidae family, but their abundance decreased when P. reticulatum was associated to the cereal. The shrub also impacted other nematode trophic groups. The abundance of opportunistic bacterial feeders (mainly Cephalobidae) was increased in shrub treatments. Further research should explore consequences on cereal nutrition and nematicidal properties of P. reticulatum

Soil microbial functional capacity and diversity in a millet-shrub intercropping system of semi-arid Senegal

International audienceA few species of shrubs grow with dryland row crops in farmers’ fields throughout the Sahel and can significantly increase crop yield. The presence of shrub roots and litter inputs should have implications for soil nutrient pool sizes but there is limited information on the interactions of these shrubs with microbial communities involved in biogeochemical processes. Therefore, the objective of this study was to determine the microbial composition and functional capacity of soil from the rooting zone of pearl millet (Pennisetum glaucum) grown in the presence or absence of the shrub Piliostigma reticulatum in Senegal. Soil samples were collected from a long-term field study where millet was cultivated alone or intercropped with P. reticulatum with annual incorporation of coppiced shrub residues. Higher nutrient contents and distinct differences in microbial communities (DGGE profiles) were found between soils from beneath the canopy compared to soil outside the influence of shrubs. The catabolic response profile (MicroResp™) showed that the soil microbial community at both shrub and non-shrub sampling locations, metabolized a wide range of substrates. Trehalose that can work as a signaling molecule was more rapidly degraded in the rooting zone of millet growing in the presence of P. reticulatum over millet alone. Urease, arylsulfatase and dehydrogenase activities in the millet root zone soil were higher when intercropped with P. reticulatum which indicates enhanced potential of biogeochemical processes to proceed in the presence of this shrub. It is concluded that the native shrub P. reticulatum promotes a more diverse and active microbial community in the rooting zone of millet and further indicates greater potential to perform decomposition and mineralize nutrients

Qualitative Detection of Proviral-DNA of HIV-1 In Infants To Determine The Efficacy of Antiretroviral Therapy In The Prevention of Vertical Transmission of HIV-1 In The Gambia

Background: The priority of the Gambia government is to eliminate maternal to child transmission of HIV and in line with this priority, the country implemented an antiretroviral therapy (ART) program. With this, all HIV infected pregnant and breastfeeding mothers and infants have access to ARV drugs. This study aims to determine the prevalence of vertical transmission of HIV among women receiving the ARV drugs. Methods: Dried blood spot samples were collected from 109 HIV-exposed infants enrolled in 13 PMTCT sites across the country. A qualitative detection of proviral-DNA of HIV-1 was performed using the Real Time Abbott PCR assay. Data from 105 mothers were analyzed using SPSS version 16.0 and association of risk factors to PCR results were analyzed using (Crosstabs) Pearson Chi-Square. The p-value of significant was set at p<0.05. Results: This study has found the prevalence of vertical transmission of HIV is 0.0% (0/64) among women that received the ARV prophylaxis then started ART, 7.1% (2/28) among mothers that received HIV prophylaxis only, and 38.4% (5/13) among women who neither receive HIV-prophylaxis nor ART during pregnancy or breastfeeding. Other risk factors of vertical transmission such as late initiation of treatment, default during treatment and first born of twins were found to be significantly associated with vertical transmission p=0.001, p=0.022 and p=0.000 respectively. Conclusion: This study has found that the early intervention of ART at the onset of pregnancy through breastfeeding can eliminates Maternal to Child transmission of HIV and a high risk of vertical transmission was found among women who neither receive prophylaxis nor ART. If the effectiveness of the antiretroviral therapy is maintain, the Gambia, in the near future will attain the WHO’s goal to eliminate Maternal to Child transmission of HIV

Human antibody response to Anopheles gambiae saliva : an immuno-epidemiological biomarker to evaluate the efficacy of insecticide-treated nets in malaria vector control

For the fight against malaria, the World Health Organization (WHO) has emphasized the need for indicators to evaluate the efficacy of vector-control strategies. This study investigates a potential immunological marker, based on human antibody responses to Anopheles saliva, as a new indicator to evaluate the efficacy of insecticide-treated nets (ITNs). Parasitological, entomological, and immunological assessments were carried out in children and adults from a malaria-endemic region of Angola before and after the introduction of ITNs. Immunoglobulin G (IgG) levels to An. gambiae saliva were positively associated with the intensity of An. gambiae exposure and malaria infection. A significant decrease in the anti-saliva IgG response was observed after the introduction of ITNs, and this was associated with a drop in parasite load. This study represents the first stage in the development of a new indicator to evaluate the efficacy of malaria vector-control strategies, which could apply in other arthropod vector-borne diseases

Insights into the genetic structure of the cowpea pest Callosobruchus maculatus in Africa

The bean beetle Callosobruchus maculatus is a worldwide generalist legume seed pest, present in the tropics and subtropics. Despite its economic importance, little is known about the population structure and migration patterns of this bruchid beetle in its continent of origin, both at local and regional scales. Gaining knowledge in the demographic processes experienced by C. maculatus, in particular in its native area, might give clues to understand evolutionary forces that have driven its expansion in traditional agroecosystems. Here, we analyze the genetic structure of 23 African populations of C. maculatus located in eleven different countries, using nuclear (28S) and mitochondrial (CytB) markers, and further apply phylogenetic and demographic analyses. The 28S sequences showed low genetic variability. In contrast, the analysis of CytB indicated significant genetic differentiation between most populations, suggesting low levels of gene flow, even at a reduced spatial scale. The results obtained from the estimation of various demographic parameters suggest evidence of recent population expansion, in agreement with a scenario of long-distance dispersal through trade of legume seeds for human consumption and population growth related to its pest nature. Overall, our results show that biogeography, isolation processes and human-mediated dispersal events drive the genetic structure of this pest in Africa