The effect of climate on the epidemiology of plague in Madagascar

Many infectious diseases of humans and animals are influenced by climate and changes in climate have an impact on future disease distribution and intensity. Understanding the processes involved is important to enable better disease prediction and effective prevention. The studies presented in this thesis aim to investigate the effects of climate on the epidemiology of plague in Madagascar. The influence of climate is explored from different angles aiming to fill some of the knowledge gaps still present in the understanding of the disease. The effect of large scale climate phenomena on inter-annual cycles of plague in Madagascar showed a change in the relationship between the El Nino Southern Oscillation the Indian Ocean Dipole and the plague incidence. To investigate the mechanisms by which climate affects the disease further, environmental variables associated with climate were examined for their effects on the spatial distribution of human plague cases in Madagascar. Altitude, vegetation cover and temperature were the main drivers identified when modelling human plague occurrence at the district level. An investigation into the micro-climate inside rat burrows, variations in flea vector abundance and vector species composition suggested that the climate in the highlands allows plague vectors, for the maintenance of the plague cycle, to be present in fairly high numbers throughout the year. A subsequent laboratory experiment obtained results on the effect of constant temperatures and humidity, as found in rodent burrows on the development stages of two plague vectors. Evidence for different climatic adaptations of the developmental stages of the species was found and development times and mortality rates differed significantly between species. X cheopis was far more successful under laboratory conditions than the endemic S. fonquerniei. However, changes in adult abundance recorded in the field did not reflect predicted changes in development rates estimated using findings from the laboratory study.EThOS - Electronic Theses Online ServiceGBUnited Kingdo