Estudio de los factores que determinan la presencia de las larvas de los mosquitos Aedes aegypti y Aedes albopictus, vectores del dengue, zika y el chikungunya, en la cuenca del río Cali, valle del Cauca, Colombia

Abstract

In Colombia, one of the main vectors of dengue is the species of Aedes aegypti and Aedes albopictus, which generate risk to approximately twenty-five million people, representing a priority problem in public health. The Valle del Cauca due to its biophysical characteristics is one of the most susceptible departments to contract the disease, for this reason this study aims to evaluate the behavior of the larvae of the Aedes aegypti and Aedes albopictus mosquito vectors of Dengue, Zika and Chicungunya.in the upper middle and lower basin of the Cali river, Valle del Cauca, Colombia, according to the environmental attributes present in each sampling station. The watershed was addressed as a unit of analysis in which the biophysical, socio-economic, cultural and institutional dimensions are involved, highlighting those factors that could have some degree of incidence in the presence and dispersion of Aedes aegypti and Aedes albopictus species.

For the collection of biological samples, a weekly sampling was carried out, during nine weeks, in each one of the described stations, inspecting all the larvitraps to proceed to the capture of the specimens. As well as the revision of the physicochemical variables (Turbidity (NTU), Total Suspended Solids (mg / L), Color (PtCo), Conductivity (μS / cm), Salinity (ppm) Total Dissolved Solids (mg / L), Dissolved oxygen (mg / L) Oxygen saturation (%), pH). weekly for nine weeks, in each of the positive larvitraps, located in the six stations, a statistical analysis was performed consecutively from the descriptive statistics, which allowed to determine the number of larval individuals of the species of Aedes aegypti and Aedes albopictus present in each of the study variables; In order to characterize the study variables, an exploratory analysis of data was carried out based on dispersion or variability indicators, which allowed us to describe the correlation between the Aedes aegypti and Aedes albopictus species with the variables: basin (High, Medium , low), the sampling stations, and container type in correlation with the physicochemical parameters obtained. To model the number of larvae according to the study parameters, we first analyzed the correlations with this variable and subsequently adjusted a Poisson regression model which explained the presence of Aedes aegypti have a function of the variables Basin, type of container and physical-chemical parameters.

The lower basin reported the highest number of records for Aedes aegypti, since its presence is subject to urban areas, which experience hotter and drier conditions, the growing process of urbanization, with the increase in population density in large cities , generates more possibility of reproduction since its behavior is closely related to the domestic environment while Aedes albopictus obtained more records in the middle basin in suburban and rural areas that are cooler and more humid, since it is more adapted to live in places with more vegetation. The results show that the species Aedes albopictus has a correlation with the rim-type container variable, which indicates preference for this medium, a situation that explains its possible adaptation to peri-urban and urban environments where innumerable artificial hatcheries can be found, (this suggestion opens a gap for further studies), its ecological flexibility allows it to colonize many types of artificial sites and urban regions. The results of the model used for this study explain the presence of Aedes aegypti and Aedes albopictus in function of the physicochemical parameters, showing dissolved oxygen oxygen saturation as the variables that most influenced the others and that probably respond to the presence of the species in the lower basin where its greatest records are found, these values give an indication that the hatcheries have a productivity, due to the high dissolved oxygen concentrations and the low toxicity.

The parameters Conductivity, Salinity and Total Dissolved Solids also present correlation because, the parameter conductivity is directly proportional to the concentration of dissolved solids, therefore the higher this concentration, the greater the conductivity, and in turn both parameters are found related to the salinity parameter, since the higher concentration of turbidity, the greater the concentration of electrolytes in water and therefore, the greater the conductivity of the medium to the transmission of an electric current), that the correlation of these three parameters favor the presence of the larvae of Aedes aegypi and Aedes albopictus mosquitoes, since the results seem to indicate that this species prefers smaller volume reservoirs, perhaps because they tend to concentrate more the dissolved and suspended solids, which would cause a greater amount of sediments and therefore of conductivity