Kasmera (Jun 2003)
Bio-ecological study of Aedes aegypti in urban ecosystems in Merida state, Venezuela 1996-1998
Abstract
In order to evaluate certain bio-ecological aspects of Aedes aegypti in the urban ecosystem in Merida State, adults of the species were captured and larva counts were made in 30% the housing units in localities of this region. It was found that positive larva deposits were greater inside housing units than outside, and this occurred both in the rainy season and the dry season, with no statistical difference between periods (X2=0.57, p< 0.05) during the three years studied. Selectivity of Aedes aegypti in relation to type of deposit area according to the larva sample was highest in old tires, followed by water tanks and water deposits, and in third place flower pots, vases, junk piles, and sheet metal containers. The capture of adults with human bait both inside and outside housing units revealed higher levels of insect (mosquito) bites in the afternoon and inside housing units, with an average of 27.2 insect bites per man hour between 7 and 8PM followed by 15.3 insect bites per man hour between 6 and 7 PM. Insect collection while insects were at rest was preferable in order to detect the presence of Aedes aegypti than capture on humans which demonstrated that insect larva counts are not the most precise indicators of insect density. Larva counts recovered relatively quickly due to the existence of stored water in zones where there are water supply difficulties and deficient water health maintenance, both of which are key factors in the epidemic occurrence of dengue in the State over the years studied. It was also found that this disease has not suffered changes in its behavior, and remains in the same areas and in the same types of water deposits even after the strong selective pressure exerted by the use of chemical insecticides applied in this region of the country.
