Regulation of the Prevalence and Intensity of Schistosomiasis in Man: Immunology or Ecology?

摘要: The belief that immunity (resistance to reinfection) is a major factor controlling the prevalence and intensity of schistosomiasis in man deepseated one. It seems impossible most observers subjects endemic areas who are exposed infested waters not constantly reinfected. Furthermore, there continuous trickle anecdotal evidence for infectivity parasite supplied by case reports individuals from nonendemic became infected (in some cases, heavily) after only short-term exposures. Even though worms do multiply human body, their ability live 20-30 years would suggest worm burdens should steadily increase level resulting severe morbidity mortality. Nevertheless, world we can detect relatively little disease death due schistosomal infection. when examine infection relation age, usually see curve which reaches its peak teens declines with advancing years. occurrence an obvious phenomenon. As Smithers has stated, "there no sudden immunologic crisis leading elimination subsequent development strong immunity. Instead, appears develop gradually, taking several become pronounced; early stages infection, may be partial, but nevertheless vital importance limiting infection" [2]. Attempts study resistance reinfection have been exceed-