pathogens Systematic Review Rickettsiales in Italy Cristoforo Guccione 1, Claudia Colomba 1,2, Manlio Tolomeo 1, Marcello Trizzino 2, Chiara Iaria 3 and Antonio Cascio 1,2,* 1 Department of Health Promotion, Mother and Child Care, Internal Medicine and Medical Specialties-University of Palermo, 90127 Palermo, Italy; [email protected] (C.G.); [email protected] (C.C.); [email protected] (M.T.) 2 Infectious and Tropical Disease Unit, AOU Policlinico “P. Giaccone”, 90127 Palermo, Italy; [email protected] 3 Infectious Diseases Unit, ARNAS Civico-Di Cristina-Benfratelli Hospital, 90127 Palermo, Italy; [email protected] * Correspondence: [email protected] Abstract: There is no updated information on the spread of Rickettsiales in Italy. The purpose of our study is to take stock of the situation on Rickettsiales in Italy by focusing attention on the species identified by molecular methods in humans, in bloodsucking arthropods that could potentially attack humans, and in animals, possible hosts of these Rickettsiales. A computerized search without language restriction was conducted using PubMed updated as of December 31, 2020. The Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) methodology was followed. Overall, 36 species of microorganisms belonging to Rickettsiales were found. The only species identified in human tissues were Anaplasma phagocytophilum, Rickettsia conorii, R. conorii subsp. israelensis, R. monacensis, R. massiliae, and R. slovaca. Microorganisms transmissible by bloodsucking arthropods could cause humans pathologies not yet well characterized. It should become routine to study the pathogens present in ticks that have bitten a man and at the same time that molecular studies for the search for Rickettsiales can be performed routinely in people who have suffered bites from bloodsucking arthropods. Citation: Guccione, C.; Colomba, C.; Tolomeo, M.; Trizzino, M.; Iaria, C.; Keywords: Rickettsiales; Rickettsia; Ehrlichia; Orientia; Anaplasma Cascio, A. Rickettsiales in Italy. Pathogens 2021, 10, 181. https:// doi.org/10.3390/pathogens10020181 1. Introduction Academic Editor: John Stenos Rickettsiales is an order of α-proteobacteria characterized by intracellular tropism Received: 31 December 2020 with a wide variety of hosts. They are small, gram-negative bacteria that reside free Accepted: 4 February 2021 Published: 8 February 2021 in the host cell cytoplasm, and some of them can be transmitted to human hosts by arthropod vectors such as ticks, lice, fleas, and mites. As suggested by Szokoli et al. we Publisher’s Note: MDPI stays neutral considered included in this order only 3 families: Rickettsiaceae, Anaplasmataceae, and with regard to jurisdictional claims in Candidatus Midichloriaceae. Rickettsiales encompass human and animal pathogens as well published maps and institutional affil- a lot of endosymbiont of arthropods, helminths, and algae with various, pathogenic or iations. not manifestation in the host. The family Rickettsiaceae includes 2 genera: Rickettsia and Orientia. A modern classification based on whole-genome analysis divides the species of the genus Rickettsia in four groups: spotted fever group (R. rickettsii, R. conorii, R. parkeri, and several others), typhus group (R. prowazekii and R. typhi), ancestral group (R. bellii and R. canadensis, not known to be pathogenic), and transitional group (R. akari, R. australis, and Copyright: © 2021 by the authors. R. felis Orientia tsutsugamushi Licensee MDPI, Basel, Switzerland. )[1–3] is the etiologic agent of scrub typhus, a rickettsiosis This article is an open access article that is widespread in Asia, the islands of the western Pacific and Indian Oceans, and distributed under the terms and foci in northern Australia [4]. The family Anaplasmataceae includes the genera Ehrlichia, conditions of the Creative Commons Anaplasma, Wolbachia, and Neorickettsia. Only the members of the first two genera have Attribution (CC BY) license (https:// been associated to human diseases. The genus Ehrlichia includes six species: E. canis, creativecommons.org/licenses/by/ E. chaffeensis, E. ewingii, E. muris, E. ovis, and E. ruminantium. The genus Anaplasma includes 4.0/). A. marginale, A. centrale, A. ovis, A. mesaeterum, A. platys, and A. phagocytophilum; only the Pathogens 2021, 10, 181. https://doi.org/10.3390/pathogens10020181 https://www.mdpi.com/journal/pathogens Pathogens 2021, 10, x FOR PEER REVIEW 2 of 26 A. centrale, A. ovis, A. mesaeterum, A. platys, and A. phagocytophilum; only the last is associ- ated to human diseases. The family Candidatus Midichloriaceae does not include any bac- teria associated to human disease. Almost all the cases of human rickettsial diseases in Italy are cases of Mediterranean Pathogens 2021, 10, 181 spotted fever (MSF) caused by R. conorii transmitted by the brown dog tick2 of 27 Rhipicephalus sanguineus. In Italy, about 400 cases of MSF are reported every year, most of which in people residing in Sicily, Sardinia and Southern Italy with a lethality of less than 3% [5] However,last is associated other pathologies to human diseases. such as The Tibola/Debonel family Candidatus (Tick Midichloriaceae Borne Lymphadenopathy does not /Der- maceincludentor anyBorne bacteria Necrosis associated Erythema to human and disease. Lymphadenopathy [6]) and many other Rickettsia spp. orAlmost subspecies all the have cases been of human identified rickettsial in recent diseases years in Italy in humans, are cases vector of Mediter- arthropods and ranean spotted fever (MSF) caused by R. conorii transmitted by the brown dog tick animalsRhipicephalus [6]. Other sanguineus rickettsioses. In Italy, about that have 400 cases been of MSFhistorically are reported documented every year, mostin Italy of are murine typhuswhich and in people epidemic residing typhus in Sicily, [5] Sardinia. Since and 1950, Southern only Italysporadic with a cases lethality of of murine less than typhus have been3% reported, [5] However, and other Italy pathologies currently such appears as Tibola/Debonel to be free (Tickof epidemic Borne Lymphadenopa- typhus. As in other Eu- ropeanthy/Dermacentor countries, Borneimported Necrosis cases Erythema of rickettsial and Lymphadenopathy pox, African [6 tick]) and-bite many fever other (ATBF), and scrubRickettsia typhusspp. have or subspecies been reported have been [5] identified. in recent years in humans, vector arthro- pods and animals [6]. Other rickettsioses that have been historically documented in Italy areThe murine purpose typhus of and this epidemic study typhusis to take [5]. Sincestock 1950, of the only situation sporadic caseson Rickettsiales of murine in Italy by focusingtyphus haveattention been reported, on the andgenera Italy currentlyuntil now appears identified to be free by of molecular epidemic typhus. methods As in in humans, in bloodsuckingother European countries,arthropods imported that could cases of potentially rickettsial pox, attack African humans, tick-bite and fever in (ATBF), animals possible hostsand of scrub these typhus Rickettsiales have been. reportedOur research [5]. has therefore mainly focused on the genera Rick- The purpose of this study is to take stock of the situation on Rickettsiales in Italy by ettsiafocusing, Anaplasma attention, Ehrlichia on the genera, and until Orientia now identified as these by are molecular the ones methods notoriously in humans, associated in with humanbloodsucking pathology arthropods until now. that could potentially attack humans, and in animals possible hosts of these Rickettsiales. Our research has therefore mainly focused on the genera 2. MaterialsRickettsia, Anaplasma and Methods, Ehrlichia, and Orientia as these are the ones notoriously associated with human pathology until now. For the writing of this review a computerized search without language restriction was2. conducted Materials and using Methods PubMed. The search was performed combining the terms “Ricketts * ANDFor Italy”, the writing “Ehrlichi of this * AND review Italy” a computerized and “Anaplasma search without AND language Italy”, Orientia restriction AND Italy”. Thewas Preferred conducted Reporting using PubMed. Items The searchfor Systematic was performed Reviews combining and the Meta terms- “RickettsAnalyses * (PRISMA) AND Italy”, “Ehrlichi * AND Italy” and “Anaplasma AND Italy”, Orientia AND Italy”. The methodologyPreferred Reporting was followed Items for Systematic[7]. Only Reviewsstudies andthat Meta-Analyses provided data (PRISMA) about method-Rickettsiales identi- fiedology by molecular was followed methods [7]. Only studiesin Italy that were provided included data aboutin theRickettsiales review. Allidentified molecular by methods whichmolecular reached methods the species in Italy werelevel included were considered. in the review. A Allflow molecular chart summarizing methods which the literature researchreached approach the species levelis reported were considered. in Figure A flow 1. chart summarizing the literature research approach is reported in Figure1. Figure 1. Process of selection of articles for the review according to PRISMA methodology [7]. Figure 1. Process of selection of articles for the review according to PRISMA methodology [7]. *: *: Bibliography. Bibliography. Pathogens 2021, 10, 181 3 of 27 3. Results A total of 818 papers were retrieved by our search, of these 220 were duplicate and removed; the remains were assessed through their title and abstract and so other 273 were excluded; the selected 325 articles