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Modeling of spatio-temporal variation in plague incidence in Madagascar from 1980 to 2007
Emanuele Giorgi1, Katharina Kreppel2, Peter J Diggle1
1Lancaster Medical School, Lancaster University, Lancaster, UK.
Abstract:
Plague is an infectious disease caused by the bacterium Yersinia pestis, which, during the fourteenth century, caused the deaths of an estimated 75-200 million people in Europe. Plague epidemics still occur in Africa, Asia and South America. Madagascar is today one of the most endemic countries, reporting nearly one third of the human cases worldwide from 2004 to 2009. The persistence of plague in Madagascar is associated with environmental and climatic conditions. In this paper we present a case study of the spatio-temporal analysis of plague incidence in Madagascar from 1980 to 2007. We study the relationship of plague with temperature and precipitation anomalies, and with elevation. A joint spatio-temporal analysis of the data proves to be computationally intractable. We therefore develop a spatio-temporal log-Gaussian Cox process model, but then carry out marginal temporal and spatial analyses. We also introduce a spatially discrete approximation for Gaussian processes, whose parameters retain a spatially continuous interpretation. We find evidence of a cumulative effect, over time, of temperature anomalies on plague incidence, and of a very high relative risk of plague occurrence for locations above 800 m in elevation. Our approach provides a useful modeling framework to assess the relationship between exposures and plague risk, irrespective of the spatial resolution at which the latter has been recorded.
Insights
Plague incidence in Madagascar is linked to environmental factors. Higher elevations and cumulative temperature anomalies increase plague risk, highlighting the need for targeted interventions.
Area of Science:
- Epidemiology
- Environmental Science
- Spatial Analysis
Background:
- Plague, caused by Yersinia pestis, remains a threat, with Madagascar being a highly endemic country.
- Environmental and climatic conditions are key factors in plague persistence.
- Understanding spatio-temporal patterns is crucial for effective disease control.
Purpose of the Study:
- To analyze the spatio-temporal distribution of plague in Madagascar from 1980 to 2007.
- To investigate the relationship between plague incidence and environmental factors like temperature, precipitation, and elevation.
- To develop a robust statistical modeling framework for plague risk assessment.
Main Methods:
- Spatio-temporal log-Gaussian Cox process model utilized.
- Marginal temporal and spatial analyses performed due to computational challenges.
- Spatially discrete approximation for Gaussian processes introduced for continuous interpretation.
Main Results:
- Evidence of a cumulative effect of temperature anomalies on plague incidence over time.
- Significantly higher relative risk of plague observed at elevations above 800 meters.
- Identified key environmental drivers influencing plague occurrence in Madagascar.
Conclusions:
- Environmental factors, particularly elevation and temperature anomalies, play a significant role in plague epidemiology in Madagascar.
- The developed modeling framework is adaptable for assessing plague risk across different spatial resolutions.
- Findings can inform targeted public health interventions and disease prevention strategies.
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