https://orcid.org/0000-0001-9133-2307
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ABSTRACT
Background: Leptospirosis is an important public health problem in Sri Lanka. Most people become infected by contact with leptospires in soil and in surface water. Survival of leptospires in the environment depends upon the moisture in soil, humidity, temperature and surface water. Leptospires are spread by flood water and waterways. Therefore, the weather of an area influences the leptospirosis incidence of that area.
Objectives: To find out the correlations between the leptospirosis incidence in the district of Kandy, Sri Lanka, and local weather variables and then to explore the utility of the findings.
Methods: We gathered data on reported leptospirosis cases in the Kandy district and mid-year population data and calculated weekly incidences for 2006 to 2015. Daily weather data from Katugastota weather station was obtained and converted into weekly data. We plotted time series graphs and observed the correlation between six aggregated weather parameters and leptospirosis incidence. Those weather parameters were rainfall, the count of wet days per week, days with rainfall >100 mm per week, minimum temperature, average temperature and average humidity. Then we looked for correlations between leptospirosis incidence and those weather parameters by performing the wavelet analysis.
Results: Our wavelet analysis results show peaks of wet days per week, days with rainfall >100 mm per week, minimum temperature, average temperature and average humidity respectively after 2, 3, 13, 20 and 1 week lags were followed by peaks of leptospirosis incidence. Nadirs (troughs) of rainfall after a week were followed by nadirs of leptospirosis incidence.
Conclusions: All weather parameters studied are correlated with local leptospirosis incidence and the climate in Kandy is conducive for leptospirosis transmission. Leptospirosis incidence in the Kandy district is high compared to the national and global incidence. Therefore, leptospirosis preventive work in Kandy deserves more attention, especially during months with favorable weather for leptospirosis transmission.
Video abstract
Responsible Editor Peter Byass, Umeå University, Sweden
Responsible Editor Peter Byass, Umeå University, Sweden
Acknowledgments
The authors sincerely thank all those who cooperated with them in this study and getting it published.
Disclosure statement
No potential conflict of interest was reported by the authors.
Ethics and consent
The study was approved by the Ethics Review Committee of the Faculty of Medicine, Peradeniya University of Sri Lanka (2018/EC/22).
Paper context
Local weather affects the survival of pathogenic leptospira bacteria in soil and surface water from which people become infected. We have studied the interrelationship between 6 local weather parameters and leptospirosis incidence of Kandy district, Sri Lanka, for 10 years. They were correlated with 1–20 weeks average lag periods. We found that leptospirosis incidence in the Kandy district is high and local weather is conducive to leptospirosis transmission.
Additional information
Funding
Notes on contributors
N. D. B. Ehelepola
NDBE conceived and designed the study and did the literature survey, NDBE collected data and did preliminary analysis, WPD cross-checked the data, KA performed the wavelet analysis and wrote that section of the manuscript, NDBE wrote the manuscript except the methodology and results of wavelet analysis, KA and WPD reviewed the original draft. All authors have read and approved the final manuscript.
