Evaluation of the effects of Azadirachtin on internal structures of Rhodnius prolixus head using low-energy X-ray microfluorescence

Abstract

Rhodnius prolixus is the main triatomine insect vector of Chagas Disease, which affects between 6 and 8 million individuals, with approximately 12,000 deaths per year in Latin America. Azadirachtin is a drug that causes changes in several species of insects, including triatomines, thereby inhibiting their development.This work exploits Low-Energy X-Ray Microfluorescence (LEXRF) to evaluate the distribution of oxygen and sodium in the structures of the insect Rhodnius prolixus, and to understand the effects of azadirachtin treatment. Specimens of fifth-instar nymphs of Rhodnius prolixus were taken from the colony of the Laboratory of Biochemistry and Physiology of Insects (Oswaldo Cruz Foundation (FIOCRUZ), Brazil) and were divided in two groups. In the first group, the insects were fed with defibrinated rabbit blood containing azadirachtin and the other group only with simply defibrinated rabbit blood. Both groups were examined at the TwinMic soft X-ray microscopy synchrotron beamline, (Elettra Sincrotrone Trieste, Trieste, Italy), providing elemental map distribution of oxygen which was correlated to the high-resolution morphological information obtained by the simultaneous absorption and differential phase contrast images.Prior to Low-Energy X-Ray Microfluorescence (LEXRF) measurements two control samples were scanned at the SYRMEP beamline (Elettra Sincrotrone Trieste, Trieste, Italy) by microtomography for an overview of the structures that were subsequently studied at TwinMic. The results allowed us to compare the differences in structures of the head of Rhodnius prolixus providing new insights into the insect's development that may be of significance toward the control of the Chagas Disease.