Amblyomma aureolatum Genetic Diversity and Population Dynamics Are Not Related to Spotted Fever Epidemiological Scenarios in Brazil.

Karla Bitencourth,Gilberto Gazêta,Marinete Amorim,Stefan Oliveira

doi:10.3390/pathogens10091146

Abstract

Regional differences in tick-borne disease epidemiology may be related to biological variations between vector populations. Amblyomma aureolatum (Ixodida: Ixodidae), a neotropical tick, is known from several regions in Brazil. However, only in the metropolitan area of São Paulo (SP) state are there studies that establish its role as a vector of a pathogenic rickettsia (Rickettsia rickettsii). The aim of the study was to analyze the genetic diversity, population dynamics, and rickettsia infection in A. aureolatum populations from different spotted fever scenarios in Brazil. Samples were subjected to DNA extraction, amplification and sequencing of 12S rDNA, cytochrome oxidase subunit II and D-loop mitochondrial markers for tick population analyses, and gltA, htrA, ompA, and ompB genes for rickettsia researches. Of the 7–17 tick haplotypes identified, 5–13 were exclusive to each population and 2–12 for each epidemiological scenario, as well as three haplotypes shared by all populations. Amblyomma aureolatum populations are expanding, and do not appear to be genetically structured vis-a-vis the different epidemiological scenarios studied. Rickettsia bellii (in SP) and Rickettsia felis (in Santa Catarina) were identified as infecting A. aureolatum. No relationship between tick haplotypes and rickettsia types were observed.

Highlights

Ticks are very important to world public health as vectors of a variety of bioagents
The same haplotype was detected with different rickettsia species, and the same rickettsia species was found in different A. aureolatum haplotypes (Table S4). This is the first study to provide a better understanding of spotted fever (SF) epidemiology by integrating A. aureolatum population genetics data using mitochondrial genes and rickettsia infection
The number of identified haplotypes (7–17) was relatively small when compared to other Amblyomma species that are involved in the SF scenario in Brazil [12,13] (Tables S1–S3)

Summary

Introduction

Ticks are very important to world public health as vectors of a variety of bioagents. Brazilian spotted fever (BSF), the main tick-borne zoonotic disease in Brazil, is caused by Rickettsia rickettsii and transmitted by Amblyomma sculptum Berlese, 1888 (the star tick) and Amblyomma aureolatum (the yellow dog tick) [1]. Knowledge of BSF vectors and epidemiology, including the vector–pathogen–host interaction, is key for effective disease control strategies in the context of One Health. Such knowledge is still incipient, especially for A. aureolatum. Records of A. aureolatum are restricted to the neotropical region, being found in the southeastern region of South America, from Uruguay to Surinam, including records for northeastern Argentina, eastern Paraguay, French Guiana, and Brazil (largely in the states of the south and southeast regions) [2]. There are records of A. aureolatum in the Pampa biome, in southern Brazil, where winters reach freezing, but summers are hot and dry e.g., [4,5,6]

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Conclusion