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Impacts de l'environnement sur les diarrhées infantiles à Madagascar : Analyse du risque Campylobacter

Abstract : Diarrheal diseases remain a major cause of infant mortality in developing countries (DCs). Due to the lack of technical platforms, the etiologic diagnoses are rarely made and treatments are then probabilistic. In Madagascar data on diarrhea are often fragmented and old. The sentinel surveillance network developed by the Institut Pasteur of Madagascar from 2007 allowed us to study the spatial and temporal distribution of consultations for diarrhea. But this syndromic surveillance cannot be coupled to biological monitoring for many diseases. In this context, we have no information on the causative agents of diarrhea. To achieve the coupling of syndromic and etiologic data, we performed a case-control study conducted in 2008-2009 in children less than 5 years in 14 districts. We have identified at least one pathogen in more than half of the children (55%), with a predominance of parasitic etiologies (37.2% diarrhea), followed by bacteria (15%) and viruses (6.7% rotavirus). Parasites were the only etiologies for which pathogenicity has been demonstrated. Among the bacterial etiologies, Campylobacter infection was the most common (9.5%). To better understand the role of Campylobacter in the occurrence of diarrhea in children and analyze the effect of environmental factors, we initiated and coordinated a dynamical cohort study including of children before the age of 24 months and followed up till the age of 36 months in Moramanga site, where the prevalence of Campylobacter was highest during the 2008 study (20.6%). Diarrhea surveillance was conducted two times per week and asymptomatic carriers assessed at baseline and every 2 months. A family study has been implemented and bi-annual stool follow-up in poultry population, water points and community drinking water for families. Campylobacter monitoring in poultry focused on rectal swabs. From January 2010 to May 2012, 508 children - corresponding to 256,346 child days -participated in the study. The overall prevalence of Campylobacter isolation was 9.3%. More than two fifths of children (43.3%) had at least one episode of Campylobacter during follow-up. The annual incidence of diarrhea and symptomatic infections were low, respectively 0.7 episodes / child and 5.8 episodes /100 children, can be explained by the low level of environmental exposure of children. We have studied the role of host factors such as age. The peak of Campylobacter infection is between 18 to 29 months, the diarrhea between 6 to 11 months then decreases. The first Campylobacter infection was always pathogen in the youngest children. It happens to the eighth month of life for 10% of them. Reinfections are at different distances from the initial event according to the age. This pattern of infection may reflect a variation of the immune competence according the age and / or acquired immunity over time after repeated exposure of the children. The local environment may have an indirect impact on maintaining protective immunity expressed by a high rate of asymptomatic infection. However, it is necessary to continue cohort study with immunologic data in a high risk transmission area as the current understanding of the interactions between the host, the environment and Campylobacter does not explain the variability of the clinical expression of infection.
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Rindra Vatosoa Randremanana. Impacts de l'environnement sur les diarrhées infantiles à Madagascar : Analyse du risque Campylobacter. Médecine humaine et pathologie. Université de Grenoble, 2012. Français. ⟨NNT : 2012GRENS040⟩. ⟨tel-00872059⟩



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