Factors that modify the larval indices of Aedes aegypti in Colima, Mexico

Abstract

In order to investigate the variables that could have the greatest impact on larval indices of Aedes aegypti, the main vector of dengue, a descriptive, longitudinal study was carried out in the city of Colima, which is located in the Mexican Pacific coastal state of the same name. A total of 187 dwellings were inspected to determine the house index (HI) and the number of positive containers per house (C+/H), during the rainy season and the dry season. The following were recorded as independent variables: the air temperature, the season, the use of ultra low volume (ULV) spraying of malathion, the Premise Condition Index (PCI), and the score on a survey of knowledge, attitudes, and practices (KAP). Both the multivariate logistic regression and the multivariate lineal regression showed a reduction of HI and C+/H due to the effect of the dry season. Paradoxically, the temperature seemed to have a negative correlation with the larval indices, and this effect was more pronounced during the dry season. The PCI showed the most significant correlation with HI and C+/H, independently of the other variables. The ULV sprayings showed a small negative effect on the indices, while the KAP score did not indicate any association at all. Some conclusions that can be drawn from this study are as follows: higher temperatures can reduce the larval indices during the dry season, the PCI can be an adequate estimator of the Ae. aegypti infestation rate, ULV spraying reduces the number of larval breeding sites, and the KAP score has little association with the larval indices.