Study of integument adaptations in deltamethrin and amidine resistant specimens of Rhipicephalus microplus and Amblyomma sculptum.

• Grant number: 21/09075-0
• Support Opportunities: Scholarships in Brazil - Post-Doctoral
• Start date: February 01, 2022
• End date: January 31, 2025
• Field of knowledge: Biological Sciences - Parasitology
• Principal Investigator: Ana Carolina de Souza Chagas
• Grantee: Renata da Silva Matos
• Host Institution: Embrapa Pecuária Sudeste. Empresa Brasileira de Pesquisa Agropecuária (EMBRAPA). Ministério da Agricultura, Pecuária e Abastecimento (Brasil). São Carlos , SP, Brazil

Abstract

Rhipicephalus microplus populations resistant to deltamethrin (pyrethroid) and amtitraz (amidine) are increasingly common and changes in the cuticular layers may contribute to the reduction of penetration of these drugs, contributing to the evolutionary success of these phenotypes. On the other hand, little is known about the sensitivity of Amblyomma sculptum, the main transmitter of Brazilian Spotted Fever, in relation to these molecules. The presence of this species parasitizing cattle is increasingly common on rural properties and the efficient and integrated control of both species needs to be better evaluated and made available. Thus, this project aims to investigate the possible morphological adaptations of the integument of engorged females of R. microplus and A. sculptum resistant to deltamethrin and amitraz and to evaluate the susceptibility of non-engorged larvae and engorged females of A. sculptum to these same ones. compounds. For this purpose, engorged larvae and females of R. microplus from Embrapa will be exposed to deltamethrin and amitraz by testing larvae packages and by teleogina immersion and will have their mortality rates and biological parameters evaluated and compared to larvae and larvae parameters. females from the sensitive Porto Alegre (POA) strains. In the following steps, in order to demonstrate changes in the morphology and lipid profile of the cuticular layers of females resistant to the compounds, the techniques of Light Microscopy (bright field), Scanning Electron Microscopy, Gas Chromatography, evaluation of the degree of cuticle plasticity, influence of pH and quantification of chitin present in the integument. All tests and analyzes mentioned will also be carried out with the species A. Sculptum from Embrapa. Thus, it is intended to elucidate mechanisms for the development of resistance to these chemical bases in order to fill huge gaps in the literature regarding the understanding of these phenomena.