Parasitology



Heterogeneous model of schistosomiasis transmission and long-term control: the combined influence of spatial variation and age-dependent factors on optimal allocation of drug therapy


D. GURARIE a1c1 and C. H. KING a2
a1 Department of Mathematics, Case Western Reserve University, 10900 Euclid Avenue, Cleveland, Ohio 44106, USA
a2 Center for Global Health and Diseases, Case Western Reserve University, 10900 Euclid Avenue, Cleveland, Ohio 44106, USA

Article author query
gurarie d   [PubMed][Google Scholar] 
king ch   [PubMed][Google Scholar] 

Abstract

Prior field studies and modelling analyses have individually highlighted the importance of age-specific and spatial heterogeneities on the risk for schistosomiasis in human populations. As long-term, large-scale drug treatment programs for schistosomiasis are initiated in subSaharan Africa and elsewhere, optimal strategies for timing and distribution of therapy have yet to be fully defined on the working, district-level scale, where strong heterogeneities are often observed among sublocations. Based on transmission estimates from recent field studies, we develop an extended model of heterogeneous schistosome transmission for distributed human and snail population clusters and age-dependent behaviour, based on a ‘mean worm burden+snail infection prevalence’ formulation. We analyse its equilibria and basic reproduction patterns and their dependence on the underlying transmission parameters. Our model allows the exploration of chemotherapy-based control strategies targeted at high-risk behavioural groups and localities, and the approach to an optimal design in terms of cost. Efficacy of the approach is demonstrated for a model environment having linked, but spatially-distributed, populations and transmission sites.

(Received March 18 2004)
(Revised June 8 2004)
(Revised July 8 2004)
(Accepted July 8 2004)


Key Words: schistosomiasis; prevention and control; infection control/economics; drug therapy/supply and distribution; praziquantel; model.

Correspondence:
c1 Department of Mathematics, 220 Yost Hall, Case Western Reserve University, 10900 Euclid Avenue, Cleveland, Ohio 44106-7058, USA. Tel: +1 216 368 2857. Fax: +1 216 368 5163. E-mail: dxg5@cwru.edu


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