Dr
Bruno Senghor
Current Organisation
Institut de recherche pour le developpement (IRD)
Current Job Title
Researcher at IRD
Biography
Publications
We report the main characteristics of 'Bacillus dakarensis' P3515(T) sp. nov., 'Bacillus sinesaloumensis' P3516(T) sp. nov., 'Gracilibacillus timonensis' P2481(T) sp. nov., 'Halobacillus massiliensis' P3554(T) sp. nov., 'Lentibacillus massiliensis' P3089(T) sp. nov., 'Oceanobacillus senegalensis' P3587(T) sp. nov., 'Oceanobacillus timonensis' P3532(T) sp. nov., 'Virgibacillus dakarensis' P3469(T) sp. nov. and 'Virgibacillus marseillensis' P3610(T) sp. nov., that were isolated in 2016 from salty stool samples (\textgreater/=1.7% NaCl) from healthy Senegalese living at Dielmo and N'diop, two villages in Senegal.
Background: Global changes are reshaping the distribution of vector-borne diseases by spreading vectors to previously non-endemic areas. Since 2013, urogenital schistosomiasis has emerged in Corsica and threatens European countries. Gastropod vectors release schistosome larvae that can infect humans who come into contact with freshwater bodies. Monitoring schistosomiasis host vectors is a prerequisite to understand and subsequently to control this pathogen transmission. Because malacological surveys are time consuming and require special expertise, the use of a simple molecular method is desirable.
Methods: The aim of this study is to develop a ready-to-use protocol using the LAMP (loop-mediated isothermal amplification) method to detect environmental DNA of Bulinus truncatus, vector of Schistosoma haematobium. Interestingly, LAMP method possesses all the characteristics required for adaptability to field conditions particularly in low-income countries: speed, simplicity, lyophilized reagents, low cost and robustness against DNA amplification inhibitors. We have tested this new method on Corsican water samples previously analysed by qPCR and ddPCR.
Results: We demonstrate that our diagnostic tool B. truncatus eLAMP (Bt-eLAMP) can detect the eDNA of Bulinus truncatus as effectively as the two other methods. Bt-eLAMP can even detect 1/4 of positive samples not detectable by qPCR. Moreover, the complete Bt-eLAMP protocol (sampling, sample pre-process, amplification and revelation) does not require sophisticated equipment and can be done in 1 ½ h.
Conclusions: LAMP detection of environmental DNA provides large-scale sensitive surveillance of urogenital schistosomiasis possible by identifying potentially threatened areas. More generally, eLAMP method has great potential in vector-borne diseases and ecology.
Bulinus senegalensis and Bulinus umbilicatus, two sympatric freshwater snails found in temporal ponds in Senegal, were thought to be involved in the transmission of Schistosoma haematobium and/or Schistosoma curassoni. To better understand the role of these Bulinus species in the transmission of human and animal Schistosoma species, B. senegalensis and B. umbilicatus were collected in 2015, during a malacological survey, from a temporal pond in Niakhar, central Senegal. Snails were induced to shed cercariae on two consecutive days. Individual cercariae from each snail were collected and preserved for molecular identification. Infected snails were identified by analysis of a partial region of the cytochrome c oxidase subunit 1 (cox1) gene. Six individual cercariae shed from each infected snail were identified by analyses of the cox1, nuclear ITS and partial 18S rDNA regions. Of the 98 snails collected, one B. senegalensis had a mixed infection shedding S. haematobium, S. bovis and S. haematobium-S. bovis hybrid cercariae and one B. umbilicatus was found to be shedding only S. haematobium. These data provide molecular confirmation for B. senegalensis transmitting S. bovis and S. haematobium-S. bovis hybrids in Senegal. The multiple Bulinus species involved in the human urogenital schistosomiasis in Senegal provides a high force of transmission warranting detailed mapping, surveillance and regular treatment of at-risk populations.
ulinus senegalensis and Bulinus umbilicatus, two sympatric freshwater snails found in temporal ponds in Senegal, were thought to be involved in the transmission of Schistosoma haematobium and/or Schistosoma curassoni. To better understand the role of these Bulinus species in the transmission of human and animal Schistosoma species, B. senegalensis and B. umbilicatus were collected in 2015, during a malacological survey, from a temporal pond in Niakhar, central Senegal. Snails were induced to shed cercariae on two consecutive days. Individual cercariae from each snail were collected and preserved for molecular identification. Infected snails were identified by analysis of a partial region of the cytochrome c oxidase subunit 1 (cox1) gene. Six individual cercariae shed from each infected snail were identified by analyses of the cox1, nuclear ITS and partial 18S rDNA regions. Of the 98 snails collected, one B. senegalensis had a mixed infection shedding S. haematobium, S. bovis and S. haematobium-S. bovis hybrid cercariae and one B. umbilicatus was found to be shedding only S. haematobium. These data provide molecular confirmation for B. senegalensis transmitting S. bovis and S. haematobium-S. bovis hybrids in Senegal. The multiple Bulinus species involved in the human urogenital schistosomiasis in Senegal provides a high force of transmission warranting detailed mapping, surveillance and regular treatment of at-risk populations.
Project Title
Hybridization as a driver for the spread of schistosomiasis: an integrative approach to evaluate the invasive capacity of schistosome hybrids under praziquantel pressure
EDCTP Project
TMA2018CDF-2370
EDCTP Program
EDCTP2
EDCTP Project Call
Career Development Fellowship (CDF)
Host Organisation
| Department | Institution | Country |
|---|---|---|
| Institut de Recherche pour le Développement - Senegal (IRD) | SN |
Project Objectives
Our overall objective is to characterise at the molecular and phenotypic level the hybrid populations between S. haematobium and S. bovis in Senegal to better assess their potential spread and their sensitivity to PZQ. Specific Objectives: To quantify the prevalence and intensities of schistosomiasis in human populations; To study the outcomes of hybridization between S. haematobium and S. bovis on snail infectivity; To evaluate the sensitivity of hybrid schistosome populations to PZQ according to parasite genetic introgression level; To characterize the frequency of hybrids and their level of genomic introgression.
Study Design
clinical trial
Project Summary
Schistosomiasis is a parasitic disease that exists in humans and cattle. Human schistosomiasis is one of the most important neglected tropical diseases with an estimated 800 million people at risk in 78 countries. The disease affects 240 million people in low- and middle-income countries in the tropics with more than 200,000 deaths per year. Sub-Saharan Africa countries are the most affected with 90% of the total cases, especially among school-aged children, farmers and fishermen who are the main populations at risk. Animal schistosomiasis is also a very common infection in Africa and Asia, where an estimated 165 million animals are infected. Since in schistosomiasis endemic areas, people and livestock often frequent the same freshwater points, hybridization between human and animal schistosome species can occur with the risk of zoonotic transmission. This is the case in northern Senegal, where hybridization between human-specific schistosome species (Schistosoma haematobium) and a cattle-specific (Schistosoma bovis) is now known to be common in children and adults. The overall objectives of the project are: to quantify the baseline prevalence and intensity of schistosomiasis in human populations; study the results of hybridization between S. haematobium and S. bovis on the infectivity of snails; assess the sensitivity of hybrid schistosome populations to PZQ according to the level of genetic introgression of the parasite using hamsters as an experimental model; characterize the frequency of hybrids and their level of genomic introgression under PZQ pressure. To achieve our objectives, we realized a baseline parasitological survey (S0) in 1,050 children aged 5 to 11 years in 5 villages to quantify the prevalence and baseline intensity of schistosomiasis then a first treatment with praziquantel (T1) was given for all positive children. One month after T1, a second parasitological survey (S1) were cared to control the T1 efficacy in 226 children recruited for follow-up. Six to seven month after treatment, selected participants were surveyed (S2) for the control of the first reinfection (R1) following by a second treatment (T2) and its efficacy control at S3. At each of the next follow survey point (S4, S5 and S6), the second reinfection (R2) at S4 and the third reinfection (R3) at S6 were recorded. This summary for publication reports the global results for the infection dynamic from S0 to S6. A total of 777 children were enrolled in five villages at baseline (S0). Out of them, 464 (59.7%) were infected by S. haematobium. Very high prevalence was found at S0 in the villages of Guia (91.2%) and Khodit (90.6%) frequenting the irrigation canal while moderate prevalence was noted in the village of Ndiawara (45%), and Dioundou (49%) using the river and also in the village of Mbane (43.1%) near the Lac de Guiers. Significant differences in the prevalence intensity of infection were noted between the types of water access. One month after T1 (S1), the heavy infections were drastically reduced from 64.6% to 1.7% in average. The lowest cure rate (88.5%) was obtained in the village using the irrigation canal with high parasite loads before treatment, while high cure rates (96.5% and 98%) and egg reduction rates between 96.7% and 99.7% was observed in all villages. The reinfection rates R1 (46.8 %), R2 (58.8%) and R3 (12.5%) varied from a year to another but were significantly higher in the village near the irrigation canal. Furthermore, at each time point of the survey, from S0 to S6 the schistosome miracidia isolated on FTA cards will be analysis at genomic level. The comparison of the miracidia genomic diversity between the baseline and the following survey points will allow us to see the percentage of pure parasites and hybrids between S. haematobium and S. bovis before and after treatment. Thus, we will verify our hypothesis which was the S. haematobium-S. bovis hybrids are lest sensible to PZQ than the pure parental species and to get an idea on the possible impact of the pressure of the PZQ repeated treatment on the parasites genetic diversity and also possibly detection of PZQ tolerance genes. Therefore, the societal impact of this project is still relevant and will concern not only Senegal but also the others tropical and sub-tropical countries that are endemic for schistosomiasis and even Europe where schistosome hybrids were recently emerged.