Changes in morphohistologic larvae of Aedes aegypti (Linnaeus, 1762) (Diptera, Culicidae) caused by tannins catechin isolated from the plant Magonia pubescens (Sapindaceae)

Abstract

The control of Aedes aegypti is nowadays one of the major public health problems
in Brazil, being the main vector of dengue and urban yellow fever. Of African
origin, this mosquito is well adapted to Brazilian climatic conditions and is now
distributed in all states. The usual methods to combat and control the mosquito have
been highly questioned. The chemical insecticides currently used have led to the
emergence of resistant populations of mosquitoes and the consequent increase of
its density, causing significant epidemics of dengue. Insecticides of botanical origin
have shown to be alternative candidates to their control. This work presents for
the first time, morphohistologic changes caused by the larvicidal activity of tannin
catechin extracted from Magonia pubescens on larvae of A. aegypti, showing the
potential of this natural larvicidal compound. Larvae of the 3rd stage were submitted
to a water solution of tannin catechins, at 37ppm, where they remained for up to 24
h. Larvae that reached lethargic state were collected and fixed in paraformaldehyde
at 4%, in sodium cacodylate buffer at 0.1 M and pH 7.2, included in resin, mounted
on slides, stained with hematoxylin-eosin and analyzed by light microscope. The
main cell toxic effects of tannin catechin on larvae of A. aegypti were the high
vacuolation and absence of cytoplasmic limits, vesicular apical formation with
release of cytoplasmic content, increase in intercellular spaces and detachment of
cells from the basal membrane.