Rickettsiaceae in two reptile-associated tick species, Amblyomma exornatum and Africaniella transversale: First evidence of Occidentia massiliensis in hard ticks (Acari: Ixodidae)

Sándor Hornok,Jenő Kontschán,Nóra Takács,Anne-Lise Chaber,Ali Halajian,Sándor Szekeres,Attila D Sándor,Olivier Plantard

doi:10.1016/j.ttbdis.2021.101830

Abstract

All species of hard ticks associated with reptiles as hosts throughout their life cycle, are currently assigned to genera including Amblyomma and Africaniella. Among these species, based on literature data, Africaniella transversale has never been investigated for the presence of tick-borne pathogens. In this study, seven DNA extracts (two from A. transversale and five from Amblyomma exornatum) were screened for the presence of important tick-borne protozoa (piroplasms) and bacteria (Anaplasmataceae and Rickettsiaceae) with conventional PCRs and sequencing. A new heat shock protein chaperonin (groEL) gene-specific PCR was also developed to identify Occidentia spp. in these samples.In A. transversale, Occidentia massiliensis (previously detected in rodent-associated soft ticks) and Rickettsia hoogstraalii were present. While the latter was molecularly identical with formerly reported sequences of this rickettsia, the genotype of O. massiliensis was new based on sequence and phylogenetic analyses of its groEL gene. In A. exornatum, a Rickettsia genotype closely related to R. tamurae and R. monacensis, was detected. The ompA sequence of this genotype was identical to that of Rickettsia sp. Ae-8 reported from A. exornatum in a reptile breeding facility in the USA.These results show that A. transversale might carry O. massiliensis which (unless having a symbiotic nature in ticks) may originate either from the reptile host of this hard tick species or the rodent prey of reptiles. This is also the first detection of the reptile tick-associated Rickettsia sp. Ae-8 (phylogenetically aligning with R. tamurae, R. monacensis) in Africa, i.e. within the original geographical range of A. exornatum.

Highlights

Among hard ticks (Acari: Ixodidae), Amblyomma species occur throughout the tropical and sub-tropical regions of the world (Gugliel mone et al, 2014)
These results show that A. transversale might carry O. massiliensis which may originate either from the reptile host of this hard tick species or the rodent prey of reptiles
All samples were negative for piroplasms. Both samples of A. transversale were positive in the 16S rRNA gene PCR. Both sequences were 100% (301/301 bp) identical to that of the origi nally described type strain of O. massiliensis (Rick ettsiales: Rickettsiaceae), reported from the soft tick Ornithodoros sonrai collected in rodent burrows, in Senegal (GenBank: NR_149,220: Mediannikov et al, 2014a)

Summary

Introduction

Among hard ticks (Acari: Ixodidae), Amblyomma species occur throughout the tropical and sub-tropical regions of the world (Gugliel mone et al, 2014). The taxonomy of this genus is currently under revision. The primary usage of reptiles as a food source only occurs in tick species formerly, or still, listed in the genus Amblyomma, i.e., around 30 species are usual or exclusive parasites of reptiles from the order Squamata (Horak et al, 2006; Guglielmone et al, 2014) While these reptile-associated tick species can occasionally parasitize higher verte brate hosts (Horak et al, 2018), they are not thought to play any role in the transmission of pathogens. These ticks will readily have access to tick-borne pathogens from reptiles

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