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C. Vera

Bio: C. Vera is an academic researcher. The author has contributed to research in topics: Schistosoma haematobium & Bulinus truncatus. The author has an hindex of 6, co-authored 15 publications receiving 153 citations.

Papers
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Journal Article
TL;DR: This study shows that the main types of aquatic environments on the Niger act as high risk areas for schistosome transmission, which strongly suggests a lack of isolation in schistoome populations and a circulation of the parasite genome through the mobility of infected human populations in Sahel zone.
Abstract: A populational study of the compatibility be- tween Scliistosoma lzaematobiurn and its potential vectors has been carried out in the Niger, confronting samples of S. haeinatohiunz populations from three epidemiologic foci with Bulinus populations originating from the same focus (sympatric infection) and with Bulinus populations from other foci (allopatric infections). The three transmis- sion foci selected were irrigation canals in ricefields along the Niger river where one finds: Bulinus truncatus rohlfsi, Bidinus globosus, Bulinus forskalii and Bulinus senegalensis; temporary pools in the Sahel area where one finds B. trzmca- tus and B. senegalensis; permanent pools of the "guelta" type in Sahara area where only B. truncatus occurs. As a compatibility test, the snail infection test was selected, with particular emphasis on optimising its reliability. Snail-in- fection experiments showed that B. trzmcatus.and B. sene- galensis are very good potential vectors, with infection rates ranging between 71.5 and 85.9%. B. globosus and B. forska- Zii, on the other hand, are totally incompatible. The mean in- fection percentages in the sympatric and allopatric combi- nations carried out with the S. haenzatobiuin-B. truncatus couple were very similar. This character strongly suggests a lack of isolation in schistosome populations and a circula- tion of the parasite genome through the mobility of infected human populations (Peuls and Touaregs) in Sahel zone. This study, in relation with snail surveys carried out in par- allel, shows that the main types of aquatic environments on the Niger act as high risk areas for schistosome transmis- sion.

37 citations

Journal Article
TL;DR: Three years after the single mass treatment on schistosomiasis morbidity, the morbidity did not reach the initial level and the effectiveness of the treatment is better in the pond system where the transmission is seasonal.
Abstract: Although it is established that the treatment by praziquantel reduces the urinary lesions due to Schistosoma haematobium, the frequency of mass treatment necessary to maintain a low morbidity level remains poorly known. The objective of this work was to study the impact over three years of a single praziquantel mass treatment on schistosomiasis morbidity in two different systems of disease transmission in Niger. The study was performed in 2 villages hyperendemic for schistosomiasis in the South-West of Niger presenting respectively 2 different systems of schistosomiasis transmission: Koutoukale-Zeno (K Zeno), located close to an irrigated area of the Niger River Valley where the transmission is permanent, and Teguey located along a temporary pond where the transmission is seasonal. After the initial evaluation (1994), we carried out a survey 3 years later (1997) except in K. Zeno where an intermediate evaluation was performed 10 months after the initial survey (1995). Approximately 300 randomised people have been examined as follows: macroscopic examination of urine and reagent sticks for macro- and micro-haematuria, filtration and microscopic examination of urine for Schistosoma eggs, and ultrasound scan of the urinary tract for morbidity. The therapeutic coverage has reached 69.9% in K. Zeno and 78.2% in Teguey. The prevalence of infestation decreased from 74.1% to 56.4 % in K. Zeno (p or = 50) went in the same time from 9.9% to 12.8% (p = 0.3) in K. Zeno and from 9.1% to 3.3% in Teguey (p = 0.01). Using ultrasound scan, the prevalence of the bladder lesions reached its previous level in both villages. However the prevalence of hydronephrosis decreased from 21.1% to 3.9% in K. eno (p < 0.001) and from 12.6% to 4.2% in Teguey (p < 0.001). Three years after the single mass treatment, the morbidity did not reach the initial level. The effectiveness of the treatment is better in the pond system where the transmission is seasonal. The lesions of the upper tract decreased more slowly than the bladder lesions, but a long time after the treatment. The re-infestation induced the re-appearance of the bladder lesions sooner than the lesions of the upper tract. The periodicity of the treatment should be variable according to the transmission system. It should occur every 2 years in irrigated areas and could be delayed (3 years) in temporary ponds. The control was beneficial in the pond system and induced a significant reduction of the severe lesions.

25 citations

Journal ArticleDOI
TL;DR: Un programme de lutte contre the bilharziose urinaire au Niger ayant pour objectif la réduction de the morbidité, nous avons conduit une enquête afin d'évaluer la régression des lésions après traitement par praziquantel, de décrire the vitesse de réinfestation and de déterminer the périodicité de the chimiothérapie
Abstract: During a Schistosoma haematobium morbidity control program in Niger, we conducted a survey to describe rhe resolution of lesions after treatment with praziquantel. to determine reinfection rates and to define retreatment schedules. 114 schoolchildren (7-15 years old) living in an hyperendemic village underwent 10 successive examinations over 34 months following an initial evaluation and the administration of 40 mg/kg of praziquantel. All children, whether apparently infected with S. haematobium or not, were treated. Egg output, microhaematuria, visual aspect of urine and abnormalities of the urinary tract by ultrasound were assessed. The initial prevalence tif infection was 74.5%. Reinfection began 5 months after treatment and the final prevalence was 47.1%. Bladder abnormalities decreased rapidly, but incompletely, probably due to reinfestation: initial prevalence: 89.5%). Their prevalence increased 8 months after treatment to 72.4% at month 34. Dilatations of the upper urinary tract regressed more slowly but constantly until the end of the study (initial prevalence: 43%; 4.6% at month 34), Three years after treatment, despite reinfection, the general morbidity level (prevalence and severity of lesions) was lower than at baseline in our cohort, which would suggest the advantage of a long interval between mass treatments in the epidemiological context of our survey.

25 citations

01 Jan 2001
TL;DR: There was an increase in knowledge about the illness in the program zone in comparison with the control area, and changes in behaviour in relation to the illness remained low, while the notion of reinfestation remains little known.
Abstract: L’objectif de ce travail etait d’evaluer l’effet des activites de sensibilisation des populations dans le cadre d’un projet de lutte contre la bilharziose urinaire, au Niger. Nous avons conduit une enquete dans deux groupes de villages endemiques nigeriens situes au bord du fleuve Niger : un groupe de villages ou se font des activites de sensibilisation (villages cibles du projet) et un village temoin (ou ne se deroule aucune activite de sensibilisation). Au total, 577 personnes ont ete interrogees au cours de cette enquete. Le projet a constitue la principale source d’information des populations sur la bilharziose dans la zone d’intervention du projet. La connaissance des mesures de lutte contre la bilharziose est moyennement acquise. En effet, 46,6 % des sujets interroges dans la zone d’intervention du projet ignorent tout moyen de lutte contre la bilharziose. Dans la zone, 41,5 % des personnes interroges ignorent l’intervention d’un hote intermediaire dans la transmission de la bilharziose urinaire. La notion de reinfestation demeure peu connue. Les comportements favorisant de la maladie sont ignores par un tiers des personnes interrogees dans la zone d’intervention du projet. Cependant, il y a un relevement indiscutable des connaissances sur la maladie dans la zone du projet par rapport a la zone temoin. Malgre ce rehaussement du niveau de connaissance, l’adoption de bons comportements par rapport a la maladie demeure timide. Seulement 33 % des sujets de la zone d’intervention ont declare avoir adopte au moins un bon comportement. Les changements de comportement sont lents a se mettre en place. Les activites d’education pour la sante doivent etre soutenues sur un longue periode pour une perennisation des benefices de la lutte contre les bilharzioses.

10 citations


Cited by
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Journal ArticleDOI
TL;DR: A meta-analysis of experimental work from 57 host-parasite systems across 54 local adaptation studies is presented to directly test theoretical predictions concerning the effect of each attribute on parasite adaptation and finds that studies of parasites with higher migration rates than their hosts report local adaptation significantly more often.
Abstract: The study of parasite local adaptation, whereby parasites perform better on sympatric hosts than on allopatric hosts and/or better on their own host population than do other parasites, is of great importance to both basic and applied biology. Theoretical examination of host-parasite coevolution predicts that parasite migration rate, generation time and virulence all contribute to the pattern of parasite local adaptation, such that parasites with greater dispersal ability, more frequent reproduction and/or high virulence ought to exhibit increased infectivity on local hosts. Here, we present a meta-analysis of experimental work from 57 host-parasite systems across 54 local adaptation studies to directly test theoretical predictions concerning the effect of each attribute on parasite adaptation. As expected, we find that studies of parasites with higher migration rates than their hosts report local adaptation, as measured by infection success, significantly more often than studies of parasites with relatively low migration rates. Furthermore, this synthesis serves to identify biases in the current body of work and highlight areas with the greatest need for further study. We emphasize the importance of unifying the field with regard to experimental methods, local adaptation definitions and reported statistics for cross-infection studies.

347 citations

Journal ArticleDOI
TL;DR: The case for the control of schistosomiasis has been strengthened by research by SCI teams and the principle that a national programme using ‘preventive chemotherapy’ can be successfully implemented in sub-Saharan Africa, whenever the resources are available.
Abstract: Schistosomiasis remains one of the most prevalent parasitic diseases in developing countries. After malaria, schistosomiasis is the most important tropical disease in terms of human morbidity with significant economic and public health consequences. Although schistosomiasis has recently attracted increased focus and funding for control, it has been estimated that less than 20% of the funding needed to control the disease in Africa is currently available. In this article the following issues are discussed: the rationale, development and objectives of the Schistosomiasis Control Initiative (SCI)-supported programmes; the management approaches followed to achieve implementation by each country; mapping, monitoring and evaluation activities with quantifiable impact of control programmes; monitoring for any potential drug resistance; and finally exit strategies within each country. The results have demonstrated that morbidity due to schistosomiasis has been reduced by the control programmes. While challenges remain, the case for the control of schistosomiasis has been strengthened by research by SCI teams and the principle that a national programme using 'preventive chemotherapy' can be successfully implemented in sub-Saharan Africa, whenever the resources are available. SCI and partners are now actively striving to raise further funds to expand the coverage of integrated control of neglected tropical diseases (NTDs) in sub-Saharan Africa.

292 citations

Journal ArticleDOI
TL;DR: A mathematical model of the dynamics of the parasite—host interaction where parasite infectivity and host susceptibility are defined by the matching of genotypes in a diploid system is developed and predicts dynamic polymorphisms where parasite allele frequencies track host allele frequencies but with a lag.
Abstract: Ebert (1994) has proposed the rule that parasites are, with few exceptions, more infective to sympatric hosts than to allopatric hosts. We test this rule using field data for schistosome infections of planorbid snails and find that, although sympatric parasite-host combinations do tend to be more compatible, there are exceptions where particular allopatric parasite-host populations are significantly more compatible. We develop a mathematical model of the dynamics of the parasite-host interaction where parasite infectivity and host susceptibility are defined by the matching of genotypes in a diploid system, The model predicts dynamic polymorphisms where parasite allele frequencies track host allele frequencies but with a lag. Because of this lag, it is possible for allopatric combinations to be more compatible than sympatric combinations. Any 'rule' that precludes this possibility is unlikely to prove robust.

194 citations

Journal ArticleDOI
TL;DR: The current status of scientific and technical progress in the development of new neglected tropical disease vaccines is reviewed, highlighting the successes that have been achieved (cysticercosis and echinococcosis) and identifying the challenges and opportunities forDevelopment of new vaccines for NTDs.
Abstract: The neglected tropical diseases (NTDs) represent a group of parasitic and related infectious diseases such as amebiasis, Chagas disease, cysticercosis, echinococcosis, hookworm, leishmaniasis, and schistosomiasis Together, these conditions are considered the most common infections in low- and middle-income countries, where they produce a level of global disability and human suffering equivalent to better known conditions such as human immunodeficiency virus/acquired immunodeficiency syndrome and malaria Despite their global public health importance, progress on developing vaccines for NTD pathogens has lagged because of some key technical hurdles and the fact that these infections occur almost exclusively in the world's poorest people living below the World Bank poverty line In the absence of financial incentives for new products, the multinational pharmaceutical companies have not embarked on substantive research and development programs for the neglected tropical disease vaccines Here, we review the current status of scientific and technical progress in the development of new neglected tropical disease vaccines, highlighting the successes that have been achieved (cysticercosis and echinococcosis) and identifying the challenges and opportunities for development of new vaccines for NTDs Also highlighted are the contributions being made by non-profit product development partnerships that are working to overcome some of the economic challenges in vaccine manufacture, clinical testing, and global access

146 citations

Journal ArticleDOI
TL;DR: It was shown that children lightly infected with S. haematobium had lower P. falciparum densities than those not infected, suggesting a negative interaction between both parasites.
Abstract: Studies with animal models have suggested the possibility of interactions between parasites during con- current infections and have raised the question of a similar phenomenon in humans. The present survey was undertaken to assess the impact of urinary schistosomiasis on the susceptibility of children to malaria. It was carried out in Senegal between September 2001 and March 2002 among 523 children 3-15 years of age. We tested the association between Plasmodium falciparum densities and the load of Schistosoma haematobium egg excretion using a linear mixed model because data were not independent. After controlling for age, sex, and season, we showed that children lightly infected with S. haematobium (1-9 eggs/10 mL of urine) had lower P. falciparum densities than those not infected ( �0.34, 95% confidence interval �0.85, �0.10), suggesting a negative interaction between both parasites.

141 citations