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King Abdulaziz University (2005)

Effect of Euphorbia Schimperiana On Schistosoma Mansoni And It’s Larval Stages In Saudi Arabia

Abuljadayel, Dalia Abdullatif

Titre : Effect of Euphorbia Schimperiana On Schistosoma Mansoni And It’s Larval Stages In Saudi Arabia

Auteur : Abuljadayel, Dalia Abdullatif

Université de soutenance : King Abdulaziz University

Grade : Master 2005

Schistosomiasis is one of the most wide spread parasitic disease which is caused by digenetic trematodes of the genus Schistosoma that produce non-operculated eggs. The life cycle of this parasite includes two kinds of hosts, a definitive host and an intermediate host. Tow prepatent periods can be considered in the schistosome life cycle, one in the mammalian host, representing the time from initial infection to the first appearance of eggs in the host’s excreta, the other in the snail host, representing the time taken between infection of the snail by miracidia and emergence of cercariae. Over 200 million people in numerous tropical and subtropical countries are believed to harbour the parasites, and effective long-term control has proved difficult. Chemotherapy with orally administered antischistosomal drugs remains the best method to care for people infected by the parasites. However, this approach is rather expensive, an alternative method is to destroy the intermediate host with molluscicidal agents. No new molluscicide of any great significance has been developed in the past decades. Only one molluscicide, Bayluscide, is predominantly used in control programmes. The rising cost of proprietary molluscicides has stimulated a search for cheaper, natural compounds from plant. Besides mollusciciding, another approach to the interruption of schistosomiasis life cycle is to kill larvae. However, there are plant products which kill cercariae and / or miracidia in addition to possessing molluscicidal activity, screening for these activities is therefore relevant to the control of schistosomiasis, since a molluscicides overall efficiency is increased if it shows toxicity towards the free-living transmission stages of the parasite itself. The molluscicidal activity of Euphorbia schimperiana (Euphorbiaceae) had been determined. Main experiments were done to investigate the activity of Euphorbia schimperiana as larvicidal and schistosomicidal. For the activity of Euphorbia schimperiana as larvicidal, the LC50 and LC90 values had been calculated. In another hand, the efficacy of this extract to attenuate the larvae of Schistosoma mansoni had been investigated. Also, The characterization of Euphorbia schimperiana extract as antischistosomal drug, together with its effect as antipenetrant agent had been carried out. In addition, The morphological changes of the treated worms were noted and compared with the normal ones. The need for further investigations on another species of Euphorbiaceae to be as larvicidal and schistosomicidal was noted, so the work provides a stimulus for surveying other Euphorbiales for controlling schistosomiasis.


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