Effects of meteorological factors on epidemic malaria in Ethiopia: a statistical modelling approach based on theoretical reasoning | Parasitology | Cambridge Core (original) (raw)

Abstract

This study was conducted to quantify the association between meteorological variables and incidence of Plasmodium falciparum in areas with unstable malaria transmission in Ethiopia. We used morbidity data pertaining to microscopically confirmed cases reported from 35 sites throughout Ethiopia over a period of approximately 6–7 years. A model was developed reflecting biological relationships between meteorological and morbidity variables. A model that included rainfall 2 and 3 months earlier, mean minimum temperature of the previous month and P. falciparum case incidence during the previous month was fitted to morbidity data from the various areas. The model produced similar percentages of over-estimation (19·7% of predictions exceeded twice the observed values) and under-estimation (18·6% were less than half the observed values). Inclusion of maximum temperature did not improve the model. The model performed better in areas with relatively high or low incidence (>85% of the total variance explained) than those with moderate incidence (55–85% of the total variance explained). The study indicated that a dynamic immunity mechanism is needed in a prediction model. The potential usefulness and drawbacks of the modelling approach in studying the weather–malaria relationship are discussed, including a need for mechanisms that can adequately handle temporal variations in immunity to malaria.

References

ABEKU, T. A.,DE VLAS, S. J.,BORSBOOM, G.,TEKLEHAIMANOT, A.,KEBEDE, A.,OLANA, D.,VAN OORTMARSSEN, G. J. &HABBEMA, J. D. F. (2002).Forecasting malaria incidence from historical morbidity patterns in epidemic-prone areas of Ethiopia: a simple seasonal adjustment method performs best.Tropical Medicine and International Health 7, 851–857.CrossRefGoogle Scholar

ABEKU, T. A.,VAN OORTMARSSEN, G. J.,BORSBOOM, G.,DE VLAS, S. J. &HABBEMA, J. D. F. (2003).Spatial and temporal variations of malaria epidemic risk in Ethiopia: factors involved and implications.Acta Tropica 87, 331–340.CrossRefGoogle Scholar

BOUMA, M. J. &DYE, C. (1997).Cycles of malaria associated with El Niño in Venezuela.Journal of the American Medical Association 278, 1772–1774.CrossRefGoogle Scholar

BOUMA, M. J. &VAN DER KAAY, J. (1996).The El Niño Southern Oscillation and the historic malaria epidemics on the Indian subcontinent and Sri Lanka: an early warning system for future epidemics?Tropical Medicine and International Health 1, 86–96.Google Scholar

COX, J.,CRAIG, M.,LE SUEUR, D. &SHARP, B. (1999).Mapping Malaria Risk in the Highlands of Africa.MARA/HIMAL Technical Report.

CRAIG, M. H.,SNOW, R. W. &LE SUEUR, D. (1999).A climate-based distribution model of malaria transmission in Sub-Saharan Africa.Parasitology Today 15, 105–111.CrossRefGoogle Scholar

FONTAINE, R. E.,NAJJAR, A. E. &PRINCE, J. S. (1961).The 1958 malaria epidemic in Ethiopia.American Journal of Tropical Medicine and Hygiene 10, 795–803.CrossRefGoogle Scholar

FREEMAN, T. &BRADLEY, M. (1996).Temperature is predictive of severe malaria years in Zimbabwe.Transactions of the Royal Society of Tropical Medicine and Hygiene 90, 232.CrossRefGoogle Scholar

HAY, S. I. &LENNON, J. J. (1999).Deriving meteorological variables across Africa for the study and control of vector-borne diseases: a comparison of remote sensing and spatial interpolation of climate.Tropical Medicine and International Health 4, 58–71.CrossRefGoogle Scholar

HAY, S. I.,OMUMBO, J. A.,CRAIG, M. H. &SNOW, R. W. (2000).Earth observation, geographic information systems and Plasmodium falciparum malaria in Sub-Saharan Africa.Advances in Parasitology 47, 173–215.CrossRefGoogle Scholar

HAY, S. I.,SNOW, R. W. &ROGERS, D. J. (1998).Predicting malaria seasons in Kenya using multitemporal satellite sensor data.Transactions of the Royal Society of Tropical Medicine and Hygiene 92, 12–20.CrossRefGoogle Scholar

KILIAN, A. H. D.,LANGI, P.,TALISUNA, A. &KABAGAMBE, G. (1999).Rainfall pattern, El Niño and malaria in Uganda.Transactions of the Royal Society of Tropical Medicine and Hygiene 93, 22–23.CrossRefGoogle Scholar

LINDSAY, S. W. &MARTENS, W. J. M. (1998).Malaria in the African highlands: past, present and future.Bulletin of the World Health Organization 76, 33–45.Google Scholar

LOEVINSOHN, M. E. (1994).Climate warming and increased malaria incidence in Rwanda.The Lancet 343, 714–718.CrossRefGoogle Scholar

MYERS, M. F.,ROGERS, D. J.,COX, J.,FLAHAULT, A. &HAY, S. (2000).Forecasting disease risk for increased epidemic preparedness in public health.Advances in Parasitology 47, 309–330.CrossRefGoogle Scholar

MACDONALD, G. (1957).The Epidemiology and Control of Malaria.Oxford:Oxford University Press.

MOLINEAUX, L. (1988).Malaria: the epidemiology of human malaria as an explanation of its distribution, including some implications for control. In_Principle and Practice of Malariology_ ( ed. Wernsdorfer, W. H. &McGregor, I.), pp. 913–998. Churchill Livingstone, Edinburgh.

NÁJERA, J. A.,KOUZNETZSOV, R. L. &DELACOLLETTE, C. (1998).Malaria Epidemics: Detection and Control, Forecasting and Prevention.World Health Organization document: WHO/MAL/98.1084.

SAS INSTITUTE INC. (1999).SAS/STAT® User's Guide, Version 8.Cary, NC: SAS Institute Inc., USA.

SWAROOP, S. (1949).Forecasting of epidemic malaria in the Punjab, India.American Journal of Tropical Medicine 29, 1–17.CrossRefGoogle Scholar

THOMSON, M. C. &CONNOR, S. J. (2001).The development of malaria early warning systems for Africa.Trends in Parasitology 17, 438–445.CrossRefGoogle Scholar

TULU, A. N. (1996).Determinants of malaria transmission in the highlands of Ethiopia: The impact of global warming on morbidity and mortality ascribed to malaria.Ph.D. thesis. London School of Hygiene and Tropical Medicine, University of London.

VERBEKE, G. &MOLENBERGHS, G. (2000).Linear Mixed Models for Longitudinal Data.New York,Springer.