Disparities in Risks of Malaria Associated with Climatic Variability among Women, Children and Elderly in the Chittagong Hill Tracts of Bangladesh

Abstract

Malaria occurrence in the Chittagong Hill Tracts in Bangladesh varies by season and year, but this pattern is not well characterized. The role of environmental conditions on the occurrence of this vector-borne parasitic disease in the region is not fully understood. We extracted information on malaria patients recorded in the Upazila (sub-district) Health Complex patient registers of Rajasthali in Rangamati district of Bangladesh from February 2000 to November 2009. Weather data for the study area and period were obtained from the Bangladesh Meteorological Department. Non-linear and delayed effects of meteorological drivers, including temperature, relative humidity, and rainfall on the incidence of malaria, were investigated. We observed significant positive association between temperature and rainfall and malaria occurrence, revealing two peaks at 19 °C (logarithms of relative risks (logRR) = 4.3, 95% CI: 1.1-7.5) and 24.5 °C (logRR = 4.7, 95% CI: 1.8-7.6) for temperature and at 86 mm (logRR = 19.5, 95% CI: 11.7-27.3) and 284 mm (logRR = 17.6, 95% CI: 9.9-25.2) for rainfall. In sub-group analysis, women were at a much higher risk of developing malaria at increased temperatures. People over 50 years and children under 15 years were more susceptible to malaria at increased rainfall. The observed associations have policy implications. Further research is needed to expand these findings and direct resources to the vulnerable populations for malaria prevention and control in the Chittagong Hill Tracts of Bangladesh and the region with similar settings.

Keywords: Bangladesh; Chittagong Hill Tracts; climatic variability; malaria; vulnerable groups.

Figure 1

Bangladesh map showing the study area (Rangamati subdistrict shaded in grey) and available weather stations.

Figure 2

Time-series plots of weekly malaria cases, temperature range (weekly maximum to minimum), humidity, and rainfall in the study area.

Figure 3

3-D plot for relative risks (RR) of malaria disease along, (A) temperature, (B) rainfall, and lags produced by DLNM for all ages. The logRR are estimated with reference to 15.8 °C mean temperature and 609 mm of rainfall.

Figure 4

Overall association (relative risk) of temperature exposures with malaria over 0–15 lag weeks, by (A) age group and (B) gender in the study period. The grey shaded area represents the 95% CI for the estimated logRR for combined data (black line). The logRR are estimated with reference to 15.8 °C mean temperature and 609 mm of rainfall.