Comparison of the prevalence of Rickettsia bellii infection in Amblyomma dubitatum tick populations from endemic and non-endemic areas for Brazilian spotted fever in São Paulo state

• Grant number: 23/03964-2
• Support Opportunities: Scholarships in Brazil - Scientific Initiation
• Start date: June 01, 2023
• End date: May 31, 2024
• Field of knowledge: Agronomical Sciences - Veterinary Medicine - Preventive Veterinary Medicine
• Principal Investigator: Marcelo Bahia Labruna
• Grantee: Carlos Eduardo Camargo Fanchini
• Host Institution: Faculdade de Medicina Veterinária e Zootecnia (FMVZ). Universidade de São Paulo (USP). São Paulo , SP, Brazil

Abstract

The expansion of areas of Brazilian spotted fever (FMB) transmission in the interior of the state of São Paulo has been associated with the expansion of the population of capybaras, the main amplifying hosts of the etiologic agent of FMB (Rickettsia rickettsii) for the tick vector Amblyomma sculptum. However, many areas with the presence of capybaras and A. sculptum remain free of R. rickettsii, indicating that other factors may be involved in establishing or not establishing R. rickettsii infection in ticks in a given area. In a previous study in São Paulo state, it was observed that FMB endemic areas were differentiated from non-endemic areas by the predominance of A. sculptum in the former, as opposed to the predominance of Ambyomma dubitatum in the latter. Also, some studies have observed that exposure to a certain species of the genus Rickettsia is able to reduce the pathogenic effects of a second infection by a more pathogenic species, indicating the development of a partial immunity to a second infection. Considering that A. dubitatum ticks may be infected by R. bellii, a possible interference of R. bellii in the amplifying capacity of the capybara for R. rickettsii could explain the heterogeneous distribution of R. rickettsii in A. sculptum populations in São Paulo state. In this sense, the present project aims to compare the prevalence of R. bellii infection in A. dubitatum populations from endemic and non-endemic areas in the state, in order to verify whether or not there is an association between the prevalence of R. bellii in A. dubitatum and the circulation of R. rickettsii in these areas.