X-ray fluorescence microtomography for imaging 3D elemental characterization of chitinized structures of Rhodnius prolixus: an evaluation of triflumurom as potential tool for integrated vector control programs

In this work, we report on the particular advantages of XRF tomography, using the XRF beamline at LNLS (Brazilian Synchrotron Light Laboratory), in the study of the biological effects of treatments with triflumuron (TFM) (Starycide® sc 480 Bayer) on the fifth instar nymph of Rhodnius prolixus , the most important insect vector of Chagas' disease. Several works suggest that Triflumuron (TFM), represents a potential tool for the control of disease vectors in public health. The main purpose of this work was to investigate possible changes in 3D elemental distribution within the exoskeleton of R. prolixus treated with TFM. Fifteen specimens of fifth-instar nymphs of Rhodnius prolixus were taken from the Laboratory of Biochemistry and Physiology of Insects, Oswaldo Cruz Foundation (FIOCRUZ), Brazil, and were divided in two groups. In the first group, immediately after feeding the insects with defibrinated rabbit blood, a Starycide® containing 48 g of TFM per 100 mL, provided by Bayer (Brazil), was applied directly to the ventral surface of the abdomen of these insects. The second group, the control group, remained also unfed and was kept under the same conditions. They were sacrificed after 25 days. These two groups were compared using XRF tomography. We investigated chemical effects of treatments with Triflumurom in Rhodnius prolixus by producing three-dimensional maps of the distribution of individual elements such as Ca, Cu, Fe and Zn. The maps obtained showed significant differences between treated and control groups. These results can help to evaluate the efficacy of the growth regulator, TFM, for disrupting the development of R. prolixus fifth-instar by topical treatment. With the new 4th generation light source (SIRIUS) we expect to continue this project at the Carnaúba beamline, using an experimental station dedicated to X-ray Fluorescence Tomography in the hard X-rays energy range (5 to 20 keV). (author)