Effects of climate change on Aedes aegypti

Abstract

Climate emergency is currently recognized in the world, due to the high concentration of greenhouse gases (GHG) in the atmosphere. Temperature increase is one of the main consequences of climate change and it differently impacts biodiversity. As ectothermic organisms, insects are more susceptible to changes in temperature and many studies investigate the effects of temperature increase in insects, specially species vectors of pathogens because they threaten human health. However, the combined effect of temperature increase and CO2 concentration – the main GHG – on insect vectors is understudied. In this thesis, I investigated the effects of climate change on Aedes aegypti, species that is the primary vector of the viruses that cause Zika, chikungunya, and dengue, and it occurs in almost all tropical and subtropical regions of the world. The thesis is divided in three chapters. In the first chapter, I investigated the global pattern of research collaboration that assess “effect of temperature or climate change on Aedes aegypti”, using bibliometric analysis. Studies that investigated climate change effects on Aedes aegypti had an exponential increase in the last 15 years. Brazil and Argentina, two developing countries, appeared among the top five countries with higher publication, while other countries (e.g. India and Paraguay) that face health problems related to diseases transmitted by the species had few or no publication in the area. Then, it is essential to reinforce the international collaboration, including these countries. In the second and the third chapters, I designed experiments in a microcosm that simultaneously simulates the increase in temperature and CO2 concentration for 2100 in Manaus, Amazonas, Brazil. Four simulated climate change scenarios (SCCS) compose the microcosm, one is the current climatic condition in Manaus (Control), and the remaining three SCCS (Light, Intermediate and Extreme) simulate the B1, A1B, and A2 climate scenarios predicted by the Fourth Assessment Report of Intergovernmental Panel on Climate Change (IPCC). In the second chapter, I evaluated the effects of SCCS and predation risk on larvae survivorship, and adult emergence pattern of Aedes aegypti. Aedes aegypti larval survivorship was not affected by SCCS and predation risk, but adult emergence pattern was affected by SCCS. Warmer scenarios accelerated the emergence of Aedes aegypti adults, and the Intermediate SCCS showed a peak emergence. In the third chapter, I evaluated the antioxidant defense system (ADS) of Aedes aegypti. I tested two main enzymes of ADS, catalase (CAT) and superoxide dismutase (SOD) in Aedes aegypti larvae and adults of both sexes reared in SCCS. The ADS responses of Aedes aegypti larvae and adult females were similar, and the activity of two enzymes did not differ according to SCCS. However, enzyme activity of adult males was affected by SCCS. In summary, results from the three chapters allow me to suggest an increase in international collaboration networks to the global network, mainly connecting countries with few or no researches in this area and that may be affected by the species in future climate change scenarios. The results also agreed with predictions regarding an increase in mosquito population in a close future, and indicated that energy allocation in Aedes aegypti may differ between life stages and sexes. Furthermore, vector control and mitigation measures to reduce greenhouse gases emission should be taken seriously, to reduce the contact of mosquitos and humans, and avoid the consequences to human health.