Indicateurs de santé dans la population d'un complexe agro-industriel du Sud Cameroun

Pour étudier la répercussion sur l'état sanitaire de la population de l'implantation d'un programme de développement agro-industriel (culture de canne à sucre) au Cameroun dans les années 60 (ville de Mbandjock), nous avons analysé la distribution des prévalences des principales pathologies parasitaires par quartier, groupe ethnique, âge et sexe. Trois enseignements peuvent être retirés de ce travail : dans la zone d'étude, le développement économique ne semble pas s'être accompagné d'une dégradation de l'état de santé, puisqu'au contraire les pathologies recherchées se sont avérées moins fréquentes que dans les régions avoisinantes; les pathologies importées (loase, schistosomose) ne se sont manifestement pas implantées localement en dépit des concentrations de population entraînées par l'installation du complexe agro-industriel; les parasitoses sévissant à l'état endémique dans la région (paludisme, onchocercose, helminthiases et protozooses intestinales) sont essentiellement groupées dans quelques quartiers (pas nécessairement défavorisés sur le plan socio-économique) qui devraient faire l'objet de mesures d'intervention intégrées

Phenotypic variation in egg survival in the predatory mite Phytoseiulus persimilis under dry conditions

The predatory mite Phytoseiulus persimilis is widely used for augmentative biological control, as an effective predator of the spider mite Tetranychus urticae. However, the biocontrol efficacy of P. persimilis decreases under dry conditions. One of the reasons for this decline concerns P. persimilis’ eggs, which are sensitive to low humidity. In this study, we investigated the possibility to select for a strain of P. persimilis adapted to dry conditions. To understand the potential sources of phenotypic variation in egg survival under dry conditions, we tested the effects of genetic and environmental factors on variation in this trait. We compared egg hatching of five P. persimilis strains, under constant as well as variable humidity conditions, at 25 °C. The results show no intraspecific genetic variation among the five tested strains in egg hatching under constant and variable humidity conditions. In all five strains, less than 20% of the eggs hatched when they were exposed to constant low (60% RH) humidity conditions. However, when eggs were exposed to successive cycles of low and high humidity, a common pattern observed in the field, significantly higher hatching rates were observed. Under variable humidity conditions, more than 73% of the eggs hatched successfully, even when exposure to high humidity was limited to only 13% of the egg developmental time. Although P. persimilis eggs suffered from a high rate of water loss under constant dry conditions, they were able to compensate for this water loss when exposed to high humidity conditions for a few hours during their development. A decreased biocontrol efficacy of P. persimilis under dry conditions may be explained by a higher egg mortality when relative humidity is constantly low. Yet, when relative humidity exhibits diurnal variation, periods of high humidity may mitigate the effects of periods of low humidity during development of P. persimilis eggs.</p

Self-reported data: a major tool to assess compliance with anti-malarial combination therapy among children in Senegal

Background: Although there are many methods available for measuring compliance, there is no formal gold standard. Different techniques used to measure compliance were compared among children treated by the anti-malarial amodiaquine/sulphadoxine-pyrimethamine (AQ/SP) combination therapy, in use in Senegal between 2004 and 2006. Methods: The study was carried out in 2004, in five health centres located in the Thies region (Senegal). Children who had AQ/SP prescribed for three and one day respectively at the health centre were recruited. The day following the theoretical last intake of AQ, venous blood, and urine samples were collected for anti-malarial drugs dosage. Caregivers and children above five years were interviewed concerning children's drug intake. Results: Among the children, 64.7% adhered to 80% of the prescribed dose and only 37.7% were strict full adherent to the prescription. There was 72.7% agreement between self-reported data and blood drug dosage for amodiaquine treatment. Concerning SP, results found that blood dosages were 91.4% concordant with urine tests and 90% with self-reported data based on questionnaires. Conclusion: Self-reported data could provide useful quantitative information on drug intake and administration. Under strict methodological conditions this method, easy to implement, can be used to describe patients' behaviors and their use of new anti-malarial treatment. Self-reported data is a major tool for assessing compliance in resource poor countries. Blood and urine drug dosages provide qualitative results that confirm any drug intake. Urine assays for SP could be useful to obtain public health data, for example on chemoprophylaxis among pregnant women

Trends in malaria morbidity following the introduction of artesunate plus amodiaquine combination in M'lomp village dispensary, south-western Senegal

BACKGROUND: In Thailand, South Africa and Zanzibar, a decrease in malaria morbidity was observed following the introduction of artemisinin-based combination therapy (ACT). In Senegal, therapeutic trials supervised the in vivo efficacy of artesunate plus amodiaquine from 1999 to 2005 at the M'lomp village dispensary. The trends in malaria morbidity in this village were evaluated from 2000 to 2002. METHODS: Each year, between July and December inclusive, fevers treated with antimalarials and slide-proven, uncomplicated malaria cases were collected from dispensary health records. Data were also collected in 1998, just prior to ACT introduction. Pearson's chi square tests and Student tests were used to compare two percentages or two means respectively (alpha = 0.05). RESULTS: Between 1998 and 2002, the total number of fevers treated with antimalarials and their repetitiveness progressively decreased: From 2824 to 945 fevers and from 17.6% to 9.7% (RR1998-2002 = 0.55; [0.44-0.69]; p < 0.0001) respectively. Considering uncomplicated malaria cases only, a decrease was observed in their total number between 2001 and 2002, from 953 to 570 cases. The incidence rate and repetitiveness also decreased. The incidence rate fell from 46.1% in 2001 to 37.5% in 2002 (p < 0.0001) and the repetitiveness decreased from 13.0% in 2000 to 6.6% in 2002 (RR2000-2002 = 0.51; [0.35-0.72]; p = 0.0001). CONCLUSION: The percentage of uncomplicated malaria cases treated with ACT increased, from 18.9% in 2000 to 64.0% in 2002, making it tempting to conclude an impact on malaria morbidity. Nonetheless, the decline in incidence rate of uncomplicated malaria was slight and a lower recorded rainfall was reported in 2002 which could also explain this decline. The context in which ACT is introduced affects the impact on malaria morbidity. In M'lomp, in contrast to studies in Thailand, South Africa and Zanzibar, ACT coverage of malaria cases was low and no vector control measure was deployed. Moreover, the malaria transmission level is higher. In sub-Saharan countries, in order to optimize the impact on malaria morbidity, ACT deployment must be supported, on the one hand, by a strengthening of public health system to ensure a high ACT coverage and, on the other hand, by others measures, such vector control measures

Biological measure of compliance to Artesunate plus Amodiaquine association: interest in a Mono-Desethyl-Amodiaquine blood assay?

The deployment of Artemisinin-based Combination Therapy for treating uncomplicated malaria poses problems in the patient compliance to these new treatments. The aim of our study was to investigate the relationship between compliance to 3 days treatment with Artesunate plus Amodiaquine (AS+AQ) and the Mono-Desethyl-Amodiaquine (MDA) blood concentration on the fourth day. A reference scale of mean MDA blood concentrations was constructed in 40 healthy adults. Each concentration corresponded to the MDA level on day 3 in a subject having one of the seven compliance degrees defined by the number and sequence of drug intakes from day 0 to day 2: one single dose on day 0, day 1 or day 2; two single doses separated by 24h, on day 0 and day 1 or on day 1 and day 2; two single doses separated by 48 h, on day 0 and day 2; three single doses, on day 0, day 1 and day 2. MDA was assayed in whole blood samples by HPLC. Non-parametric Mann and Whitney U tests were used for the comparison of two means. Our results demonstrated no clear relationship between the mean MDA blood concentrations on day 3 and compliance degrees, according to neither the number nor the sequence of doses taken. In particular, even though the differences were not significant, the mean concentration after three doses, expected to be the maximum, was unexpectedly lower than after two doses, on day 0 and day 1 or on day 1 and day 2. The high inter-individual variability of MDA concentrations attributed to the different rates of hepatic metabolism of each individual appears to have a greater effect on MDA levels than the number or timing of doses. Therefore, it seems that the role of a MDA blood assay is limited in use to discerning if none or one or more doses have been taken. A MDA assay do not allow to measure the compliance degree of one patient to AS+AQ association. Presently, interview and pill count following treatment seem to be the only tools available that may permit differentiation between degrees of compliance

Diving deep into a tiny world : effects of drought on the predatory mite Phytoseiulus persimilis

Terrestrial arthropods are particularly vulnerable to drought stress, because of their small size, and because their body has a high surface-area-to-volume ratio (SA:V). In agricultural ecosystems, where the ecological functions of terrestrial arthropods are significant (herbivores, pollinators, predators), this sensitivity to drought can have serious consequences. Biological pest control with arthropod predators, in particular, is strongly affected by relative humidity conditions. Understanding how terrestrial arthropods respond to changes in humidity in their environment is, therefore, essential to ensure the success of biological control programs. In this thesis, I investigated the effects of drought stress on the predatory mite Phytoseiulus persimilis. This mite is widely used in augmentative biological control as an effective predator of the two-spotted spider mite Tetranychus urticae. The biocontrol efficacy of P. persimilis decreases under dry conditions, and this lower efficacy has often been explained as the consequence of the drought sensitivity of P. persimilis eggs. In CHAPTER 2, I investigated the presence of genetic variation for egg drought resistance in P. persimilis, and the potential sources (genetic or environmental) of phenotypic variation in this trait, by comparing egg hatching rates among five P. persimilis populations in different humidity conditions (constant low, constant high, and variable). I found no intraspecific genetic variation among the five tested populations in egg hatching under constant and variable humidity conditions. In all five populations, less than 20% of the eggs hatched when they were exposed to constant low humidity conditions (60% RH) at 25 &deg;C. However, when eggs were exposed to successive cycles of low and high humidity, significantly higher hatching rates were observed. Under variable humidity conditions, more than 73% of the eggs hatched successfully, even when exposure to high humidity was limited to only 13% of the egg developmental time. These results changed my initial perspective on the drought sensitivity of P. persimilis eggs: it appears that they are capable of dealing with harsh humidity conditions more effectively than previously thought. In CHAPTER 3, I investigated the possibilities to select for increased drought resistance in P. persimilis eggs, through artificial selection and experimental evolution. In an artificial selection trial, P. persimilis eggs from two selection lines were exposed to three selection rounds. In an experimental evolution trial, all P. persimilis life stages from two selection lines were exposed to a constant low humidity selection pressure. To evaluate the response to selection, egg hatching rate at low humidity was assessed in both trials. A significant increase in drought resistance of eggs occurred in the experimental evolution trial. Already one month after the start of the trial, egg survival at low humidity had more than doubled. However, this increase in egg drought resistance disappeared within 15 days after I had removed the selection pressure from a group of adult females. In the artificial selection trial, no response to selection was observed after three selection rounds. The results of this study indicate that drought resistance in P. persimilis eggs is a phenotypically plastic trait, regulated by their mother. This discovery raised new questions and made me change my focus from P. persimilis eggs to P. persimilis females. In CHAPTER 4, I studied the role of transgenerational phenotypic plasticity in the adaptation of P. persimilis eggs to different relative humidity conditions. For this, I exposed P. persimilis adult females to constant and variable humidity regimes, and evaluated the hatching rate of their eggs in dry conditions, as well as the survival and oviposition rates of these females. Whereas the eggs laid by P. persimilis females exposed to constant high humidity did not survive in dry conditions, females exposed to constant low humidity started laying drought-resistant eggs after 24 hours of exposure. Around 43% of the females exposed to variable humidity conditions laid drought-resistant eggs after 102 hours of exposure. Survival and oviposition rates of the females were affected by humidity: females laid fewer eggs under constant low humidity, and had a shorter lifespan under constant high and constant low humidity. These results demonstrate that P. persimilis females are able to prepare their offspring for dry conditions through an environmental maternal effect, by laying drought-resistant eggs. Under conditions of desiccation stress combined with the production of drought-resistant eggs, P. persimilis females lay fewer eggs in constant dry conditions. In CHAPTER 5, I investigated the mechanisms underlying drought resistance of P. persimilis eggs, by studying the physiological differences between drought-resistant and drought-sensitive eggs. I compared the volume of the eggs, their sex ratio, their chemical composition (by gas chromatography-mass spectrometry), their internal and external structure (by scanning electron microscope and transmission electron microscope images), and their developmental time. The results showed that drought-resistant and drought-sensitive eggs have a different chemical composition: drought-resistant eggs contain more free amino acids, sugar alcohols, and saturated hydrocarbons than drought-sensitive eggs. This difference may contribute to reducing water loss in drought-resistant eggs. Moreover, drought-resistant eggs are on average 8.4% larger in volume than drought-sensitive eggs. This larger volume, probably the result of a higher water content, may make drought-resistant eggs less vulnerable to water loss. I did not find difference in sex ratio, internal or external structure nor developmental time between drought-resistant and drought-sensitive eggs. These results mark the first step in the understanding of the strategies involved in the production of drought-resistant eggs in P. persimilis females. In conclusion, I demonstrated that P. persimilis eggs can deal with harsh humidity conditions better than we previously thought. First, they are able to recover from a long exposure to drought if they are exposed to high humidity for only a few hours. Second, through a maternal effect, P. persimilis females are able to protect their offspring against desiccation stress by laying drought-resistant eggs. As a consequence, the lower efficacy of P. persimilis in dry conditions may rather be due to a lower oviposition rate and a shorter lifespan of P. persimilis females than to the drought sensitivity of their eggs. Finally, this thesis is also a first step in understanding the internal egg structure in a phytoseiid mite species

Mise en place des combinaisons thérapeutiques à base d'artémisinine pour traiter le paludisme simple (de la théorie à la pratique)

Depuis 2001, l'OMS recommande l'utilisation des CTA pour traiter le paludisme simple, et, depuis 2006, la confirmation des cas par TDR. En théorie, 80% des malades doivent être traités par CTA et l'impact attendu est une diminution de la morbidité et mortalité palustres. L'objectif de nos recherches a donc été l'analyse de certains obstacles au succès de la mise en place des CTA, de faible recours des populations au système de soins publics, les e carts aux directives officielles dans les pratiques des soignants et l'observance partielle des malades. Ces obstacles ne sont pas spécifiques au Sénégal et se retrouvent dans d'autres pays subsahariens. A ce jour, 41 pays ont adoptés une CTA. Dans certains d'entre eux, une baisse de la morbidité et de la mortalité palustre a été documentée. Toutefois, il convient de regarder ces premiers succès avec prudence. En effet, il ne faut pas omettre l'impact majeur des autres stratégies de lutte. De plus, sur le long terme, bien que les CTA soient des traitements très efficaces, nous pensons que le contexte actuel de mise en place de ces traitements risque de compromettre leur impact. Afin de pérénniser les premiers succès, les interventions de soutien à l'introduction des CTA doivent améliorer l'accès à ces traitements et garantir leur utilisation correcte par les soignatns et les soignés. En outre, il est primordial d'adapter ces interventions aux considérations quotidiennes propres aux soignants et aux populations et les études à ce sujet devraient se poursuivre.PARIS-BIUSJ-Physique recherche (751052113) / SudocSudocFranceF

Next generation biological control – an introduction

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