Tick-Borne Rickettsioses around the World: Emerging Diseases Challenging Old Concepts

Unité des Rickettsies, CNRS UMR 6020, IFR 48, Université de la Méditerranée, Faculté de Médecine, 13385 Marseille Cedex 5, France.
Clinical Microbiology Reviews (Impact Factor: 17.41). 11/2005; 18(4):719-56. DOI: 10.1128/CMR.18.4.719-756.2005
Source: PubMed


During most of the 20th century, the epidemiology of tick-borne rickettsioses could be summarized as the occurrence of a single pathogenic rickettsia on each continent. An element of this paradigm suggested that the many other characterized and noncharacterized rickettsiae isolated from ticks were not pathogenic to humans. In this context, it was considered that relatively few tick-borne rickettsiae caused human disease. This concept was modified extensively from 1984 through 2005 by the identification of at least 11 additional rickettsial species or subspecies that cause tick-borne rickettsioses around the world. Of these agents, seven were initially isolated from ticks, often years or decades before a definitive association with human disease was established. We present here the tick-borne rickettsioses described through 2005 and focus on the epidemiological circumstances that have played a role in the emergence of the newly recognized diseases.

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    • "Dogs are considered to be the sentinels of R. conorii infection (Parola et al., 2005; Ortuño et al., 2009), which is the causative agent of Mediterranean spotted fever (MSF), one of the oldest-recognized vector-borne infectious diseases. It is transmitted by the brown dog tick, Rh. sanguineus s.l. "
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    ABSTRACT: The diverse tick fauna as well as the abundance of tick populations in Romania represent potential risks for both human and animal health. Spotted fever group (SFG) rickettsiae are recognized as important agents of emerging human tick-borne diseases worldwide. However, the epidemiology of rickettsial diseases has been poorly investigated in Romania. In urban habitats, companion animals which are frequently exposed to tick infestation, play a role in maintenance of tick populations and as reservoirs of tick-borne pathogens. Therefore, the aim of the present study was to investigate the occurrence of SFG rickettsiae in ticks infesting dogs in a greater urban area in South-eastern Romania. Adult ixodid ticks (n=205), including Rhipicephalus sanguineus sensu lato (n=120), Dermacentor reticulatus (n=76) and Ixodes ricinus (n=9) were collected from naturally infested dogs and were screened for SFG rickettsiae using conventional PCR followed by sequencing. Additionally, ticks were screened for DNA of Babesia spp., Hepatozoon spp., Ehrlichia canis, and Anaplasma platys. Four zoonotic SFG rickettsiae were identified: Rickettsia raoultii (16%) and Rickettsia slovaca (3%) in D. reticulatus, Rickettsia monacensis (11%) in I. ricinus, and Rickettsia conorii (0.8%) in Rh. sanguineus s.l. Moreover, pathogens of veterinary importance, such as B. canis (21%) in D. reticulatus and E. canis (7.5%) in Rh. sanguineus s.l. were identified. The findings expand the knowledge on distribution of SFG rickettsiae as well as canine pathogens in Romania. Additionally, this is the first report describing the molecular detection of R. conorii in ticks from Romania.
    Ticks and Tick-borne Diseases 10/2015; DOI:10.1016/j.ttbdis.2015.10.006 · 2.72 Impact Factor
    • "Rickettsia spp., 'Candidatus Neoehrlichia mikurensis' and Anaplasma phagocytophilum are bacteria from the Order Rickettsiales. They are intracellular parasites depending on eukaryotic cell (Kawahara et al., 2004; Dumler et al., 2001), transmitted by ixodid ticks and causing a febrile disease with headache, muscle pain and rash (Parola et al., 2005; Welinder- Olsson et al., 2010; Bakken and Dumler, 2006). Their importance has been increasingly recognized during last years, and new Rickettsia organisms are still being described. "
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    ABSTRACT: In this study, we screened a total of 2473 questing (years 2011-2014) and 199 engorged (years 2013 and 2014) Ixodes ricinus ticks for the presence of Rickettsia spp., "Candidatus Neoehrlichia mikurensis", Anaplasma phagocytophilum, and Babesia spp. Host-seeking ticks were collected at three study sites corresponding to natural woodland, urban park and pastureland ecosystem, and analyzed using molecular techniques. All pathogens tested were present at all study sites. The prevalence rates for Rickettsia spp., 'Candidatus Neoehrlichia mikurensis', Anaplasma phagocytophilum, and Babesia spp. ranged from 2.6% to 9.2%, 0.8% to 11.6%, 0% to 12.1%, and 0% to 5.2%, respectively. Engorged I. ricinus ticks collected from sheep on pastureland in the years 2013 and 2014 yielded prevalence rates 7.4% and 6.3%, respectively, for Rickettsia spp., 38.5% and 14.1% for 'Candidatus N. mikurensis', 18.5% and 12.5% for A. phagocytophilum, and 4.4% and 0.0% for Babesia spp. Monitoring of neglected tick-borne pathogens within the scope of epidemiological surveillance is an important tool for prevention and control of human tick-borne infections.
    Ticks and Tick-borne Diseases 10/2015; DOI:10.1016/j.ttbdis.2015.09.004 · 2.72 Impact Factor
    • "The cosmopolitan Rhipicephalus sanguineus (Arachnida: Ixodidae) parasitizes mainly dogs and occasionally affects humans (Dantas-Torres 2010). This tick transmits important pathogens to its hosts such as Rickettsia rickettsii, Ehrlichia canis, and Babesia canis that cause Rocky Mountain spotted fever, erlichiosis, and babesiosis, respectively (Parola et al. 2005; Dantas-Torres 2008). "
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    ABSTRACT: Conidia of the entomopathogenic fungus Metarhizium anisopliae (Ascomycota: Clavicipitaceae) were assessed against Rhipicephalus sanguineus (Arachnida: Ixodidae) eggs under laboratory conditions. Clusters of 25 eggs were applied either directly with the fungal conidial formulations or set on previously fungus-treated filter paper. Treatments consisted of conidia formulated in water or an oil-in-water emulsion at final concentrations of 3.3 × 10(3), 10(4), 3.3 × 10(4), 10(5), or 3.3 × 10(5) conidia/cm(2). The development of mycelium and new conidia on egg clusters incubated at 25 °C and humidity close to saturation depended on conidial concentration, formulation, and application technique. No larvae eclosed from eggs after direct applications of conidia regardless of the formulation. The eclosion and survival of larvae from indirectly treated egg clusters depended on the type of formulation and conidial concentration applied. Oil-in-water formulations of conidia demonstrated the highest activity against eggs of R. sanguineus.
    Parasitology Research 09/2015; DOI:10.1007/s00436-015-4729-z · 2.10 Impact Factor
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