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Antananarivo, Madagascar

Nicolas G.,CIRAD - Agricultural Research for Development | Nicolas G.,University Paris Est Creteil | Chevalier V.,CIRAD - Agricultural Research for Development | Tantely L.M.,Pasteur Institute of Madagascar | And 2 more authors.
PLoS Neglected Tropical Diseases | Year: 2014

Rift Valley fever (RVF) is a vector-borne zoonotic disease that causes high morbidity and mortality in ruminants. In 2008–2009, a RVF outbreak affected the whole Madagascar island, including the Anjozorobe district located in Madagascar highlands. An entomological survey showed the absence of Aedes among the potential RVF virus (RVFV) vector species identified in this area, and an overall low abundance of mosquitoes due to unfavorable climatic conditions during winter. No serological nor virological sign of infection was observed in wild terrestrial mammals of the area, suggesting an absence of wild RVF virus (RVFV) reservoir. However, a three years serological and virological follow-up in cattle showed a recurrent RVFV circulation. The objective of this study was to understand the key determinants of this unexpected recurrent transmission. To achieve this goal, a spatial deterministic discrete-time metapopulation model combined with cattle trade network was designed and parameterized to reproduce the local conditions using observational data collected in the area. Three scenarios that could explain the RVFV recurrent circulation in the area were analyzed: (i) RVFV overwintering thanks to a direct transmission between cattle when viraemic cows calve, vectors being absent during the winter, (ii) a low level vector-based circulation during winter thanks to a residual vector population, without direct transmission between cattle, (iii) combination of both above mentioned mechanisms. Multi-model inference methods resulted in a model incorporating both a low level RVFV winter vector-borne transmission and a direct transmission between animals when viraemic cows calve. Predictions satisfactorily reproduced field observations, 84% of cattle infections being attributed to vector-borne transmission, and 16% to direct transmission. These results appeared robust according to the sensitivity analysis. Interweaving between agricultural works in rice fields, seasonality of vector proliferation, and cattle exchange practices could be a key element for understanding RVFV circulation in this area of Madagascar highlands. © 2014 Nicolas et al.

Razakandrainibe R.,Pasteur Institute of Madagascar | Combes V.,University of Sydney | Grau G.E.,University of Sydney | Jambou R.,Pasteur Institute of Madagascar
International Journal of Biochemistry and Cell Biology | Year: 2013

Vascular endothelial cells (ECs) form a barrier that plays a crucial role in the health and integrity of tissues by regulating the passage of molecules, liquids and immune cells. Dysfunctions or disruption of this barrier leads to edema, inflammation, and associated pathologies. During infection, ECs control transmigration of cells by a complex system of molecules. However pathogens can hijack this pathway to invade ECs and/or tissues. They can also trigger the opening of intercellular junction, apoptosis of ECs or activation of the immune system, which in turn lead to the destruction of the endothelial wall and subsequent edema. Activation of immune cells by pathogens can also enhance the destruction of EC and edema. The review summarizes the state-of-the-art knowledge on the key steps of the complex interactions between the endothelial wall, pathogens, and the immune system that lead to the opening of junctions and/or destruction of the wall, enhancing pathology. A better understanding of these points will allow the development of adjunctive treatments to be used in combination with therapies targeting pathogens, with the aim of protecting the wall and improving the recovery of patients with severe infectious diseases. © 2013 Elsevier Ltd.

Ratovoson R.,Pasteur Institute of Madagascar | Rasetarinera O.R.,University of Antananarivo | Andrianantenaina I.,Pasteur Institute of Madagascar | Rogier C.,Pasteur Institute of Madagascar | And 3 more authors.
PLoS ONE | Year: 2015

Background: Hypertension is one of the main risk factors of cardiovascular diseases. In Madagascar, studies on hypertension in urban and rural communities are scarce. Objectives: The aim of this study was to determine the prevalence of hypertension and identify associated risk factors in adults living in a health and demographic system in Moramanga, Madagascar. Methods: The study included people aged 15 years old and above living in a health and demographic system in Moramanga. A household census was performed in 2012 to enumerate the population in 3 communities in Moramanga. In addition to the questionnaire used in the initial census, a standardized questionnaire and blood pressure were taken twice after 5 and 10 minutes of rest. In urban areas, heights and weights were also measured to calculate the body mass index. Results: There were 3621 and 4010 participants respectively in rural and urban areas. Prevalence of hypertension in rural population was 27.0%(IC95%[25.6-28.5]) and 29.7% (IC95% [28.3-31.1]) in urban population. Among hypertensive subjects, 1.7% (17/979) and 5.3% (64/1191) were on antihypertensive treatment for at least 1 month before the survey in rural and urban population, respectively. In rural areas, increasing age (65 years and older vs 18-25 years OR = 11.81, IC95% [7.79-18.07]), giving more than 3 positive responses to the usual risks factors of hypertension (OR = 1.67, IC95% [1.14-2.42]) and singles in comparison with married people (OR = 1.61, IC95% [1.20-2.17]) were associated to hypertension in a logistic regression model. In urban areas, increasing age (65 years and older vs 18-25 years OR = 37.54, IC95% [24.81-57.92]), more than 3 positive responses to the usual risks of hypertension (OR = 3.47, IC95% [2.58-4.67]) and obesity (OR = 2.45, IC95% [1.56-3.87]) were found as risk factors. Conclusion: Hypertension is highly prevalent in rural areas although it is significantly less treated. As a result, a major epidemic of cardiovascular diseases is at risk in Madagascar's progressively aging society. Copyright: © 2015 Ratovoson et al.

Ratsitorahina M.,Pasteur Institute of Madagascar | Rahelinirina S.,Pasteur Institute of Madagascar | Michault A.,University of Reunion Island | Rajerison M.,Pasteur Institute of Madagascar | And 3 more authors.
PLoS ONE | Year: 2015

Background: Leptospirosis is a widespread but underreported cause of morbidity and mortality. It has rarely been reported in either humans or animals in Madagascar. Methods: We conducted a cross-sectional survey of the inhabitants in Moramanga, Madagascar, in June 2011, to estimate the prevalence of human infection using the microscopic agglutination test (MAT). This activity was carried out as part of a workshop implemented by the Pasteur Institute of Madagascar, focusing on surveillance with a one week field study and targeting the health staff of the district level. Results: In total, we sampled 678 inhabitants from 263 households. The sex ratio (M/F) was 0.65 and the mean age 26.7 years. We obtained a value of 2.9% for the first recorded seroprevalence of this disease in the human community of Moramanga. Questionnaire responses revealed frequent contacts between humans and rodents in Moramanga. However, activities involving cattle were identified as a risk factor significantly associated with seropositivity (OR=3). Conclusion: Leptospirosis remains a neglected disease in Madagascar. This study highlights the need to quantify the public health impact of this neglected disease in a more large scale, in all the country and to establish point-of-care laboratories in remote areas. © 2015 Ratsitorahina et al.

Trape J.-F.,Institute Of Recherche Pour Le Developpement | Trape J.-F.,Aix - Marseille University | Tall A.,Pasteur Institute | Diagne N.,Institute Of Recherche Pour Le Developpement | And 23 more authors.
The Lancet Infectious Diseases | Year: 2011

Background: Substantial reductions in malaria have been reported in several African countries after distribution of insecticide-treated bednets and the use of artemisinin-based combination therapies (ACTs). Our aim was to assess the effect of these policies on malaria morbidity, mosquito populations, and asymptomatic infections in a west African rural population. Methods: We did a longitudinal study of inhabitants of Dielmo village, Senegal, between January, 2007, and December, 2010. We monitored the inhabitants for fever during this period and we treated malaria attacks with artesunate plus amodiaquine. In July, 2008, we offered longlasting insecticide (deltamethrin)-treated nets (LLINs) to all villagers. We did monthly night collections of mosquitoes during the whole study period, and we assessed asymptomatic carriage from cross-sectional surveys. Our statistical analyses were by negative binomial regression, logistic regression, and binomial or Fisher exact test. Findings: There were 464 clinical malaria attacks attributable to Plasmodium falciparum during 17 858 person-months of follow-up. The incidence density of malaria attacks averaged 5·45 (95% CI 4·90-6·05) per 100 person-months between January, 2007, and July, 2008, before the distribution of LLINs. Incidence density decreased to 0·41 (0·29-0·55) between August, 2008, and August, 2010, but increased back to 4·57 (3·54-5·82) between September and December, 2010-ie, 27-30 months after the distribution of LLINs. The rebound of malaria attacks were highest in adults and children aged 10 years or older: 45 (63%) of 71 malaria attacks recorded in 2010 compared with 126 (33%) of 384 in 2007 and 2008 (p<0·0001). 37% of Anopheles gambiae mosquitoes were resistant to deltamethrin in 2010, and the prevalence of the Leu1014Phe kdr resistance mutation increased from 8% in 2007 to 48% in 2010 (p=0·0009). Interpretation: Increasing pyrethroid resistance of A gambiae and increasing susceptibility of older children and adults, probably due to decreasing immunity, caused the rebound and age shift of malaria morbidity. Strategies to address the problem of insecticide resistance and to mitigate its effects must be urgently defined and implemented. Funding: Institut de Recherche pour le Développement and the Pasteur Institute of Dakar. © 2011 Elsevier Ltd.

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