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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

Published online by Cambridge University Press:  13 December 2004

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

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.

Type
Research Article
Copyright
© 2004 Cambridge University Press

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References

REFERENCES

AGWANDA, R. O. ( 1997). The epidemiology of Schistosoma mansoni in Machakos/Makueni Districts of Kenya: Exploratory analysis of factors affecting transmission of the parasite. Ph.D. thesis, Department of Medical Parasitology, London School of Hygiene and Tropical Medicine, London.
ANDERSON, R. M. & MAY, R. M. ( 1991 a). The basic model: statics. In Infectious Diseases of Humans. Dynamics and Control, pp. 467496. Oxford University Press, New York.
ANDERSON, R. M. & MAY, R. M. ( 1991 b). The basic model: dynamics. In Infectious Diseases of Humans. Dynamics and Control, pp. 507520. Oxford University Press, New York.
BARBOUR, A. D. ( 1978). Macdonald's model and the transmission of bilharzia. Transactions of the Royal Society of Tropical Medicine and Hygiene 72, 615.CrossRefGoogle Scholar
BARBOUR, A. D. ( 1996). Modeling the transmission of schistosomiasis: an introductory view. American Journal of Tropical Medicine and Hygiene 55, 135143.CrossRefGoogle Scholar
BAVIA, M. E., HALE, L. F., MALONE, J. B., BRAUD, D. H. & SHANE, S. M. ( 1999). Geographic information systems and the environmental risk of schistosomiasis in Bahia, Brazil. American Journal of Tropical Medicine and Hygiene 60, 566572.CrossRefGoogle Scholar
BRINDLEY, P. J. ( 1994). Drug resistance to schistosomicides and other anthelmintics of medical significance. Acta Tropica 56, 213231.CrossRefGoogle Scholar
BUTTERWORTH, A. E., DUNNE, D. W., FULFORD, A. J., OUMA, J. H. & STURROCK, R. F. ( 1996). Immunity and morbidity in Schistosoma mansoni infection: quantitative aspects. American Journal of Tropical Medicine and Hygiene 55, 109115.CrossRefGoogle Scholar
BUTTERWORTH, A. E., STURROCK, R. F., OUMA, J. H., MBUGUA, G. G., FULFORD, A. J., KARIUKI, H. C. & KOECH, D. ( 1991). Comparison of different chemotherapy strategies against Schistosoma mansoni in Machakos District, Kenya: effects on human infection and morbidity. Parasitology 103, 339355.CrossRefGoogle Scholar
CHAN, M. S., ANDERSON, R. M., MEDLEY, G. F. & BUNDY, D. A. ( 1996). Dynamic aspects of morbidity and acquired immunity in schistosomiasis control. Acta Tropica 62, 105117.CrossRefGoogle Scholar
CHAN, M. S. & BUNDY, D. A. ( 1997). Modelling the dynamic effects of community chemotherapy on patterns of morbidity due to Schistosoma mansoni. Transactions of the Royal Society of Tropical Medicine and Hygiene 91, 216220.CrossRefGoogle Scholar
CHAN, M. S., GUYATT, H. L., BUNDY, D. A., BOOTH, M., FULFORD, A. J. & MEDLEY, G. F. ( 1995). The development of an age structured model for schistosomiasis transmission dynamics and control and its validation for Schistosoma mansoni. Epidemiology and Infection 115, 325344.CrossRefGoogle Scholar
CLENNON, J. A., KING, C. H., MUCHIRI, E. M., KARIUKI, H. C., OUMA, J. H., MUNGAI, P. & KITRON, U. ( 2004). Spatial patterns of urinary schistosomiasis infection in a highly-endemic area of coastal Kenya. American Journal of Tropical Medicine and Hygiene 70, 443448.Google Scholar
EL KHOLY, H., ARAP SIONGOK, T. K., KOECH, D., STURROCK, R. F., HOUSER, H., KING, C. H. & MAHMOUD, A. A. ( 1989). Effects of borehole wells on water utilization in Schistosoma haematobium endemic communities in Coast Province, Kenya. American Journal of Tropical Medicine and Hygiene 41, 212219.CrossRefGoogle Scholar
GRYSEELS, B. ( 1996). Uncertainties in the epidemiology and control of schistosomiasis. American Journal of Tropical Medicine and Hygiene 55 (Suppl.), 103108.CrossRefGoogle Scholar
GUYATT, H. L. & TANNER, M. ( 1996). Different approaches to modeling the cost-effectiveness of schistosomiasis control. American Journal of Tropical Medicine and Hygiene 55, 159164.CrossRefGoogle Scholar
HAYNES, K. E. & FOTHERINGHAM, A. S. ( 1984). Gravity and Spatial Interaction Models. SAGE Publications, Inc., Beverly Hills, CA.
JORDAN, P. ( 1985). Schistosomiasis: The St. Lucia Project. Cambridge University Press, Cambridge.
KARIUKI, H. C., CLENNON, J. A., BRADY, M., KITRON, U., STURROCK, R. F., OUMA, J. H., TOSHA, S., NDZOVHU, M., MUNGAI, P., HAMBURGER, J., HOFFMAN, O., PELLEGRINI, C., MUCHIRI, E. M. & KING, C. H. ( 2004). Distribution patterns and cercarial shedding of Bulinus nasutus and other snails in Msambweni area, Coast Province, Kenya. American Journal of Tropical Medicine and Hygiene 70, 449456.Google Scholar
KING, C. H., BLANTON, R. E., MUCHIRI, E. M., OUMA, J. H., KARIUKI, H. C., MUNGAI, P., MAGAK, P., KADZO, H., IRERI, E. & KOECH, D. ( 2004). Low heritable component of risk for infection intensity and infection-associated disease in urinary schistosomiasis among Wadigo village populations in Coast Province, Kenya. American Journal of Tropical Medicine and Hygiene 70, 5762.Google Scholar
KING, C. H., LOMBARDI, G., LOMBARDI, C., GREENBLATT, R., HODDER, S., KINYANJUI, H., OUMA, J., ODIAMBO, O., BRYAN, P. J., MURUKA, J., MAGAK, P., WEINERT, D., MACKAY, W., RANSOHOFF, D., HOUSER, H., KOECH, D., SIONGOK, T. K. & MAHMOUD, A. A. F. ( 1988). Chemotherapy-based control of schistosomiasis haematobia. I. Metrifonate versus praziquantel in control of intensity and prevalence of infection. American Journal of Tropical Medicine and Hygiene 39, 295305.Google Scholar
KING, C. H. & MAHMOUD, A. A. ( 1989). Drugs five years later: praziquantel. Annals of Internal Medicine 110, 290296.CrossRefGoogle Scholar
KING, C. H., MUCHIRI, E. M. & OUMA, J. H. ( 1992). Age-targeted chemotherapy for control of urinary schistosomiasis in endemic populations. Memorias do Instituto Oswaldo Cruz 87, 203210.CrossRefGoogle Scholar
MacDONALD, G. ( 1965). The dynamics of helminth infections, with special reference to schistosomes. Transactions of the Royal Society of Tropical Medicine and Hygiene 59, 489506.CrossRefGoogle Scholar
MALONE, J. B., HUH, O. K., FEHLER, D. P., WILSON, P. A., WILENSKY, D. E., HOLMES, R. A. & ELMAGDOUB, A. I. ( 1994). Temperature data from satellite imagery and the distribution of schistosomiasis in Egypt. American Journal of Tropical Medicine and Hygiene 50, 714722.CrossRefGoogle Scholar
MEDLEY, G. E. & BUNDY, D. A. ( 1996). Dynamic modeling of epidemiologic patterns of schistosomiasis morbidity. American Journal of Tropical Medicine and Hygiene 55, (Suppl.) 149158.CrossRefGoogle Scholar
MIGUEL, E. & KREMER, M. ( 2004). Worms: identifying impacts on education and health in the presence of treatment externalities. Econometrica 72, 159217.CrossRefGoogle Scholar
MUCHIRI, E. M. ( 1991). Association of water contact activities and risk of reinfection for S. haematobium after drug treatment in the Msambweni Area, Kenya. M.S. thesis, Epidemiology and Biostatistics. Case Western Reserve University, Cleveland.
MUCHIRI, E. M., OUMA, J. H. & KING, C. H. ( 1996). Dynamics and control of Schistosoma haematobium transmission in Kenya: an overview of the Msambweni Project. American Journal of Tropical Medicine and Hygiene 55 (Suppl.), 127134.CrossRefGoogle Scholar
WEBSTER, J. P., DAVIES, C. M., NDAMBA, J., NOBLE, L. R., JONES, C. S. & WOOLHOUSE, M. E. ( 2001). Spatio-temporal genetic variability in the schistosome intermediate host Biomphalaria pfeifferi. Annals of Tropical Medicine and Parasitology 95, 515527.CrossRefGoogle Scholar
WORLD HEALTH ORGANIZATION ( 2002). Prevention and control of schistosomiasis and soil-transmitted helminthiasis. Report of a WHO Expert Committee, pp. 34–35. WHO, Geneva.
WOOLHOUSE, M. E. ( 1991). On the application of mathematical models of schistosome transmission dynamics. I. Natural transmission. Acta Tropica 49, 241270.Google Scholar
WOOLHOUSE, M. E. ( 1992). On the application of mathematical models of schistosome transmission dynamics. II. Control. Acta Tropica 50, 189204.CrossRefGoogle Scholar
WOOLHOUSE, M. E., DYE, C., ETARD, J. F., SMITH, T., CHARLWOOD, J. D., GARNETT, G. P., HAGAN, P., HII, J. L., NDHLOVU, P. D., QUINNELL, R. J., WATTS, C. H., CHANDIWANA, S. K. & ANDERSON, R. M. ( 1997). Heterogeneities in the transmission of infectious agents: implications for the design of control programs. Proceedings of the National Academy of Sciences, USA 94, 338342.CrossRefGoogle Scholar
WOOLHOUSE, M. E., ETARD, J. F., DIETZ, K., NDHLOVU, P. D. & CHANDIWANA, S. K. ( 1998). Heterogeneities in schistosome transmission dynamics and control. Parasitology 117, 475482.CrossRefGoogle Scholar
ZHOU, X., DANDAN, L., HUIMING, Y., HONGGEN, C., LEPING, S., GUOJING, Y., QINGBIAO, H., BROWN, L. & MALONE, J. B. ( 2002). Use of landsat TM satellite surveillance data to measure the impact of the 1998 flood on snail intermediate host dispersal in the lower Yangtze River Basin. Acta Tropica 82, 199205.CrossRefGoogle Scholar