Assessing temporal associations between environmental factors and malaria morbidity at varying transmission settings in Uganda
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Date
2016
Journal Title
Journal ISSN
Volume Title
Publisher
Malaria journal
Abstract
Environmental factors play a major role in transmission of malaria given their relationship to both the
development and survival of the mosquito and parasite. The associations between environmental factors and malaria
can be used to inform the development of early warning systems for increases in malaria burden. The objective of
this study was to assess temporal relationships between rainfall, temperature and vegetation with malaria morbidity
across three different transmission settings in Uganda.
Methods: Temporal relationships between environmental factors (weekly total rainfall, mean day time temperature
and enhanced vegetation index series) and malaria morbidity (weekly malaria case count data and test positivity
rate series) over the period January 2010–May 2013 in three sites located in varying malaria transmission settings in
Uganda was explored using cross-correlation with pre-whitening. Sites included Kamwezi (low transmission), Kasambya
(moderate transmission) and Nagongera (high transmission).
Results: Nagongera received the most rain (30.6 mm) and experienced, on average, the highest daytime temperatures
(29.8 °C) per week. In the study period, weekly TPR and number of malaria cases were highest at Kasambya and
lowest at Kamwezi. The largest cross-correlation coefficients between environmental factors and malaria morbidity for
each site was 0.27 for Kamwezi (rainfall and cases), 0.21 for Kasambya (vegetation and TPR), and −0.27 for Nagongera
(daytime temperature and TPR). Temporal associations between environmental factors (rainfall, temperature and
vegetation) with malaria morbidity (number of malaria cases and TPR) varied by transmission setting. Longer time lags
were observed at Kamwezi and Kasambya compared to Nagongera in the relationship between rainfall and number
of malaria cases. Comparable time lags were observed at Kasambya and Nagongera in the relationship between
temperature and malaria morbidity. Temporal analysis of vegetation with malaria morbidity revealed longer lags at
Kasambya compared to those observed at the other two sites.
Conclusions: This study showed that temporal associations between environmental factors with malaria morbidity
vary by transmission setting in Uganda. This suggests the need to incorporate local transmission differences when
developing malaria early warning systems that have environmental predictors in Uganda. This will result in development
of more accurate early warning systems, which are a prerequisite for effective malaria control in such a setting.
Description
Keywords
Malaria, Uganda, Cross-correlations, Early warning system, Environment
Citation
Kigozi, R., Zinszer, K., Mpimbaza, A., Sserwanga, A., Kigozi, S. P., & Kamya, M. (2016). Assessing temporal associations between environmental factors and malaria morbidity at varying transmission settings in Uganda. Malaria journal, 15(1), 1-6. DOI 10.1186/s12936-016-1549-2