title: Immunoregulation and World Health Assembly resolution 54.19: why does treatment control morbidity?
abstract: World Health Assembly resolution 54.19, passed in May, 2001, declares the intent of the World Health Organization member States to implement a combined strategy for the control of morbidity caused by schistosomiasis and soil-transmitted helminths. Among other things, the resolution urges ministries to treat all clinical cases and groups at high risk of morbidity such as children, women and those exposed occupationally. The policy is predicated on the evidence that morbidity due to these infections can be controlled by periodic treatment with appropriate chemotherapeutic, anti-helminthic drugs. While it is true that annual or biannual praziquantel treatment for schistosomiasis decreases morbidity, we now question how treatment leads to this beneficial effect. It is clear that treatment kills worms, but we propose that this is only a part of how it leads to reduced morbidity in areas of ongoing transmission and reinfection. By killing worms, we postulate that treatment also effects immunologic changes to the normal host/parasite relationship, and the resulting immune responses lead to both increased resistance (protection against reinfection), and increased immunoregulatory mechanisms that control morbidity upon subsequent reinfections. If the effects of treatment contribute to morbidity control in these ways, a better understanding of how this occurs may allow optimization of these effects of treatment through appropriate periodic treatment regimens, resulting in less reinfection and better morbidity control when reinfection does occur.
authors.affiliation: Center for Tropical and Emerging Global Diseases and Department of Microbiology, 623 Biological Sciences Building, University of Georgia, Athens, GA, 30602-2606 USA. dcolley@uga.edu
authors.forename: Daniel G
authors.initials: DG
authors.lastname: Colley
authors.forename: W
authors.initials: W
authors.lastname: Evan Secor
mesh_terms: D000818:Animals; D000871:Anthelmintics / Q000627:therapeutic use*; D006373:Helminthiasis / Q000188:drug therapy / Q000453:epidemiology* / Q000276:immunology*; D006801:Humans; D009017:Morbidity; D011223:Praziquantel / Q000627:therapeutic use*; D012552:Schistosomiasis / Q000188:drug therapy / Q000453:epidemiology* / Q000276:immunology*; D016896:Treatment Outcome; D014944:World Health Organization
chemical_list: D000871:Anthelmintics; D011223:Praziquantel