Abstract
Rickettsia rickettsii infection causes the highest human fatality rate among all Rickettsia species of the world and is endemic in Southeast Brazil. In this part of the country most human spotted fever cases are related to unnaturally high populations of ticks, usually a mix of two species, Amblyomma dubitatum Neumann and Amblyomma sculptum Berlese and their local host, capybara (Hydrochoerus hydrochaeris). At the same time, an increase in the number of SF notifications as well as its urbanization was observed, and a better characterization of disease epidemiology is mandatory for control measures and to halt its expansion. It was recently noticed in southeast Brazil that SF endemic areas were characterized by overgrowth populations of A. sculptum and decreased populations of A. dubitatum. Hence, characterization of areas with potential to endemicity, eco-epidemiological studies and control measures may rely on the evaluation of A. sculptum/A. dubitatum rate. However, in potentially endemic scenarios, discriminating the two tick species, particularly the nymphs considered the main vector stage, is a challenge in face of several hundreds to thousands of ticks that should be examined for quantitative studies. We herein present additional morphological features to an existing identification key for Amblyomma nymphs that considerably diminishes the labor to distinguish nymphs of these two tick species. Specifically, the oval-shaped scutum of A. dubitatum and a conspicuous scapula of A. sculptum are prominent discriminating features.
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Acknowledgements
Authors are indebted to Marcelo de Oliveira Gonzaga for assistance with the Stereo Zoom Microscope in the Laboratory of Arachnology (LARA) – Federal University of Uberlândia; Sebastián Muñoz-Leal for useful comments on the manuscript, and Caroline Lopes Queiroz. Authors acknowledge National Council for Scientific and Technological Development – CNPq (Academic Career Research Fellowship to M.P.J. Szabó). This work was supported by the Public Ministry of Minas Gerais, Fundação de Amparo à Pesquisa do Estado de Minas Gerais (FAPEMIG) (grant CVZ PPM 00191-16) and the Coordination for the Improvement of Higher Education Personnel - Brazil (CAPES) - Finance Code 001.
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Suzin, A., da Silva Rodrigues, V., Nascimento Ramos, V.d. et al. Comparing scapular morphology of Amblyomma sculptum and Amblyomma dubitatum nymphs allows a fast and practical differential diagnosis of ticks in highly infested areas with dominance of these two species. Exp Appl Acarol 86, 455–463 (2022). https://doi.org/10.1007/s10493-022-00702-1
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DOI: https://doi.org/10.1007/s10493-022-00702-1