CLIMATIC FACTORS DETERMINING THE PRESENCE AND ABUNDANCE OF IMMATURE STAGES OF AEDES AEGYPTI IN DROUGHT YEARS: A
Abstract:
Aedes aegypti is the principal vector of dengue virus. Its vector ability is related to its capacity to adapt to different environments and to lay eggs in diverse sites to ensure the success of its progeny. The species abundance can be studied by estimating the infestation level using the Breteau Index (BI) and the House Index (HI). These indices indirectly reveal the practices and habits of house dwellers, who accumulate containers that contribute to the presence and abundance of Ae. aegypti and the potential transmission of dengue virus. The objective of this work was to analyze the relationship between these indices and environmental variables in drought years (2004-2005). The data analyzed were taken from entomological surveillance spreadsheets of the National Ministry of Health of Argentina, and included 156,288 houses and 658,656 artificial containers inspected by Ministry technicians. A correlation matrix was generated between the indices and the climatic variables to analyze cross correlations. When the relationships between climatic variables and the indices were significant, they were adjusted with General Linear Models (GLMs) taking into consideration the lowest value of the Akaike Information Criterion (AIC). The models were validated by testing the normal distribution of the residuals and the lack of autocorrelation. The results showed that 8,249 houses and 15,165 artificial containers were positive for Ae. aegypti. The BI and HI were positively correlated with precipitation, minimum temperature and maximum temperature at a zero-month time lag. The best GLM found between HI, minimum temperature and precipitation at a zero-month time lag was a gamma model. The increase of HI was related to the mean temperature at a 1-month time lag by using a gamma GLM. This increase in the HI may be potentially related to the accumulation of containers by humans under drought conditions, a behavior that favors the growth of immature forms of the main dengue vector.
