Thèse soutenue

Cryptosporidium parvum et environnement : épidémiologie et contrôle de l'environnement hydrique

Auteur / Autrice : Xunde Li
Direction : Philippe Brasseur
Type : Thèse de doctorat
Discipline(s) : Sciences pharmaceutiques. Parasitologie
Date : Soutenance en 2000
Etablissement(s) : Rouen

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Cryptosporidium parvum oocysts are widely distributed in the environment including natural waters and water supplies and causes both human and animal infection. Waterborne cryptosporidiosis has been identified as an emerging public health problem. This parasite is resistant to most currently used water disinfectants and no effective spécifie treatment has been available. Infectivity of oocysts recovered from waters should be evaluated for estimating the risks of contamination. Variable importance in outbreaks and significance in distribution had been documented for subgenotypes of C. Parvum. In the present study, A NMRI-suckling mice model was developed for evaluation of infectivity of C. Parvum oocysts and in vitro excystation was measured as viability. Infectivity of fourteen isolates of C. Panwm oocysts were investigated and all were infective to suckling mice. Influence of temperature and durations of storage on viability, infectivity and morphology of oocysts were studied. Infectivity of oocysts stored at +10°C decreased more rapidly than that of those stored at +4°C, more contracted size and more changes in external wall structure were observed on oocysts stored at +10°C. Using polypropylene cartridge filter and Gelman Envirochek capsule filters, local environmental waters and local distribution waters were filtered respectively. C. Parvum oocysts were detected in the condensed water samples by IFA. C. Parvum oocysts were also found from condensed mussel (Mytilus edulis) tissues by IFA, IMS and PCR-sequencing. Curative anticryptosporidial activity of nitazoxanide (NTZ) was evaluated in an immunosuppressed rat model and compared with the effects of sinefungin (SNF) and paromomycin (PRM). Although the inhibition rate was lower than that of SNF and PRM, NTZ exerted a long-lasting curative anti-C. Parrwm activity in the immunosuppressed rat. Using the 18S rDNA primers, PCR were performed on 6 isolates of C. Par-tiwm oocysts from clinic AIDS patients, 1 isolate from experimentally infected calf and 2 isolates from mussels. Séquence analysis were performed on the PCR products. Two isolates frome AIDS patients were human genotype (genotype 1), the other four isolates from AIDS patients and the isolates from calf were bovine (genotype 2). The two isolates from mussels were bovine genotype.