key: cord-272536-bl8bdrcm
authors: De Vito, Andrea; Geremia, Nicholas; Mameli, Sabrina Maria; Fiore, Vito; Serra, Pier Andrea; Rocchitta, Gaia; Nuvoli, Susanna; Spanu, Angela; Lobrano, Renato; Cossu, Antonio; Babudieri, Sergio; Madeddu, Giordano
title: Epidemiology, Clinical Aspects, Laboratory Diagnosis and Treatment of Rickettsial Diseases in the Mediterranean Area During COVID-19 Pandemic: A Review of the Literature
date: 2020-09-01
journal: Mediterr J Hematol Infect Dis
DOI: 10.4084/mjhid.2020.056
sha: 
doc_id: 272536
cord_uid: bl8bdrcm

The purpose of the present review is to give an update regarding the classification, epidemiology, clinical manifestation, diagnoses, and treatment of the Rickettsial diseases present in the Mediterranean area. We performed a comprehensive search, through electronic databases (Pubmed – MEDLINE) and search engines (Google Scholar), of peer-reviewed publications (articles, reviews, and books). The availability of new diagnostic tools, including Polymerase Chain Reaction and nucleotide sequencing has significantly modified the classification of intracellular bacteria, including the order Rickettsiales with more and more new Rickettsia species recognized as human pathogens. Furthermore, emerging Rickettsia species have been found in several countries and are often associated with unique clinical pictures that may challenge the physician in the early detection of the diseases. Rickettsial infections include a wide spectrum of clinical presentations ranging from a benign to a potentially life treating disease that requires prompt recognition and proper management. Recently, due to the spread of SARS-CoV-2 infection, the differential diagnosis with COVID-19 is of crucial importance. The correct understanding of the clinical features, diagnostic tools, and proper treatment can assist clinicians in the management of Rickettsioses in the Mediterranean area.

considered to be absent in obligate intracellular bacteria. 9, 11 The transmission of the infection depends on the group. SFG is transmitted by the bite of an infected tick; whereas, organisms of typhus group are transmitted through inoculation via infected louse or flea faeces (Rickettsiae prowazekii and Rickettsia typhi, respectively) through a bite, wound or mucous membranes. Once inoculated into the skin, organisms are phagocytized by dendritic cells and transported via lymphatics to local lymph nodes where they replicate. Subsequently, the bacteria spread in the bloodstream and disseminate to infect the endothelium of the microcirculation, where the Rickettsiae can infect vascular endothelial cells of the small and mediumsized blood vessels. The damage of the endothelium and the subsequent endothelial dysfunction is followed by alteration in coagulation and the cytokine network. The endpoint of this pathogenetic results in a reduction in circulating peripheral CD4 T lymphocytes and perivascular infiltration by CD4 and CD8 T lymphocytes, B cells, and macrophages, causing a vasculitis. [12] [13] [14] Epidemiology. There are several pathological Rickettsia species in Europe, and in the last years, new species and subspecies have been implicated as human pathogens, and new rickettsial syndromes have been described. 15 Mediterranean spotted fever (MSF) caused by Rickettsia conorii subsp. conorii is the most frequent rickettsiosis in Europe. It is endemic in southern Europe, but sporadic cases have been reported in all the continents. 15, 16 The first cases were first described in Tunisia in 1909 by Conor and Buch. The brown dog tick, Rhipicephalus sanguineus, is the vector and the potential reservoir of Rickettsia conorii subsp. conorii in the Mediterranean area. 15, 17 Most MSF cases occur in summer when climatic conditions seem to be an essential factor in increasing the aggressiveness of Rhipicephalus sanguineus ticks to bite humans. [15] [16] [17] [18] Rickettsia conorii subsp. israelensis is the agent of Israeli spotted fever (ISF), which was first reported in 1946 in the Haifa Bay area, Israel. [17] [18] [19] [20] In Europe and the Mediterranean region, the brown dog tick, Rhipicephalus sanguineus, is recognized to be the vector of Rickettsia conorii subsp. israelensis. 21 The geographic distribution of the disease appears to be spread more widely in the Mediterranean countries than previously thought. Cases have been reported in Italy, Portugal, Tunisia, and Libya. [22] [23] [24] [25] Other Rickettsia conorii subspecies reported in the Mediterranean area are Rickettsia conorii subsp. caspia and Rickettsia conorii subsp. indica. The first one is the agent of Astrakhan fever, endemic in the Astrakhan region, adjacent regions of the Caspian Sea, and described in Rhipicephalus sanguineus ticks in Kosovo and southern France. 16 Rickettsia sibirica subsp. mongolitimonae, the microorganism that cause of lymphangitis-associated rickettsiosis (LAR), was isolated for the first time in China, from Hyalomma asiaticum ticks collected in Mongolia in 1991. 16 Rickettsia sibirica subsp. mongolitimonae was detected in Hyalomma anatolicum excavatumt ticks in Greece and Cyprus; in Rhipicephalus pusillus ticks in France, Portugal, and Spain; and in Rhipicephalus bursa ticks in Spain. [26] [27] [28] [29] [30] The first human infection with Rickettsia sibirica subsp. mongolitimonae was reported in France in 1996. 31 Rickettsia sibirica subsp. mongolitimonae is implicated in human pathogen in different countries, as France, Spain, Turkey, and Egypt. [32] [33] [34] [35] Rickettsia slovaca and Rickettsia raoultii are associated with a syndrome characterized by scalp eschars and neck lymphadenopathy following tick bites (SENLAT). These microorganisms have been found in Dermacentor marginatus and Dermacentor reticulatus ticks in a vast majority of European countries. [36] [37] [38] [39] [40] [41] [42] After MSF, SENLAT is the most prevalent tick-borne rickettsiosis in Europe. It has been reported in different countries, including Hungary, Spain, France, Germany, Italy, Bulgaria, and Portugal. [43] [44] [45] [46] [47] [48] SENLAT occurs most frequently from March to May and from September to November, which corresponds to the periods of most considerable activity of Dermacentor adult ticks in Europe. [47] [48] [49] Rickettsia helvetica is transmitted by Ixodes ricinus, which is the primary vector and the natural reservoir. However, human infection is rare, and it has been documented only in Austria, Denmark, France, Italy, Sweden, Slovakia, and Switzerland. 16, 50, 51 Other rare rickettsial pathological species in Europe and the Mediterranean area are Rickettsia massiliae, Rickettsia monacensis, Rickettsia aeschlimannii, and Rickettsia sibirica subsp. sibirica. Clinical Manifestation. Rickettsiosis is a rare disease: the incidence is around 1 case per 100.000 people by year, but it has been increasing during the last years, probably due to better diagnostic techniques. 15 In Europe, the most important diseases are three: Mediterranean Spotted Fever (MSF), Lymphangitisassociated rickettsioses (LAR), and scalp eschar and neck lymphadenopathy (SENLAT). 19 The other significant disease caused by Rickettsia rickettsii is the Rocky Mountain Spotted Fever (RMSF), but no cases have been reported in Europe to date. 19 Apart from these three pathologies, there are other minor forms caused by different pathogens.

Mediterranean spotted fever. MSF, caused by Rickettsia conorii, is the most common rickettsialdisease in Europe, where the highest incidence is during summer. 52 Not all people who come into contact with this bacterium develop the disease. A Spanish study, indeed, shows that 4-8% of the population carry antibodies against Rickettsia but without a previous clinical history of MSF. 53 The most common symptoms are fever (93-98%), myalgia (64-75%), headache (48-65%), and asthenia (27%). The maculopapular rash is present in 85-94% of the patients; the tache noir has been noticed in 58-64% of the patients. The classic triad, fever, maculopapular rash, and inoculation eschar, is present in 40-50% of the patients. [54] [55] [56] In most cases, MSF is a self-limiting disease but sometimes could be life-threatening. It was estimated that about 5-10% of MSF cases could be severe. [78] [79] [80] and arthritis 81, 82 have been reported.

The most frequent hematological and biochemical modifications are thrombocytopenia, leukocyte count abnormalities, elevated hepatic enzyme levels and an increase of c-reactive protein. 54, 83 Mortality was around 1-3% 84 before the antimicrobial drug era. Thus, it has been considered a benign illness. In some recent studies, MSF appears to be more severe than it has been thought. Mortality rates were 5.4% in France, 3.6% in Portugal, 3.2% in Algeria, 0.8% in Spain and 0.36% in Italy. 52, 54, [84] [85] [86] Risk factors for severe MSF include advanced age, immunodeficiency, chronic alcoholism, G6PDH deficiency, diabetes, prior prescription of an inappropriate antimicrobial drug, or delay in treatment. 84, 85 Scalp eschar and neck lymphadenopathy after a tick bite. SENLAT 87 syndrome is also known as TIBOLA 88 (tick-borne lymphadenopathy) or DEBONEL 44 (Dermacentor-borne necrotic erythema and lymphadenopathy), and it is caused by Rickettsia slovaca and Rickettsia raoultii 19 but also by other bacteria such as Bartonella henselae. 87 This disease is developed mostly during spring and autumn. 49 The clinical description of SENLAT includes asthenia, headache, painful adenopathies (especially to the neck's lymph nodes), and a painful scalp eschar surrounded by a perilesional erythematous halo. Low fever, rash, and face edema have also been reported less frequently. 45, 87, 89 No malignant or fatal cases have been described in the literature. After the therapy, alopecia could potentially last for several months, with persistent asthenia. 89 Lymphangitis-associated rickettsioses. LAR is caused www.mjhid.org Mediterr J Hematol Infect Dis 2020; 12; e2020056

by Rickettsia sibirica subsp. mongolitimonae. Just a few cases have been reported in Europe. In particular, until 2013, only 24 cases have been reported in the Mediterranean area. 19 The typical period of this disease is spring. Commons symptoms include fever, headache, an eschar (frequently more than one) on the site of inoculation, and lymphangitis, which starts from the eschar and reaches an enlarged lymph node. The difference between LAR and the other two diseases are the period of occurrence (spring), and the presence of lymphangitis and multiple eschars. 90 Until now, no deaths have been reported in patients that have been infected by Rickettsia. However, some severe cases have been reported, in particular: a retinal vasculitis, 91 sepsis with disseminated intravascular coagulation, 92 myopericarditis 93 and a septic shock. 94, 95 Mediterranean spotted fever-like. Other Rickettsiae in Europe could infect humans; most of them cause a disease very similar to MSF. For example, Rickettsia conorii subsp. caspia causes an illness called "Astrakhan fever." This disease is typical of the Caspian Sea area, but some cases have also been reported in France. 96 Astrakhan fever diverges from MSF in the percentage of patients who present with an eschar (only 20%) and because it could cause thrombocytopenia and bleed. 97 Another similar disease is the Israeli spotted Fever (ISF), caused by Rickettsia conorii subsp. israelensis. In Europe, this bacterium has been found only in Portugal and in Italy. The symptoms are quite similar to MSF except for the presence of gastrointestinal symptoms in half of the patients. The main difference is the malignity; indeed, the mortality is higher (more than 25%). 24, 40, 56, 98, 99 Other Rickettsiae who could cause a MSF-like illness are Rickettsia monacensis, 100, 101 Rickettsia massiliae, 102, 103 Rickettsia aeschlimannii, 104, 105 and Rickettsia helvetica which could be malignant. 51, 106, 107 Differential Diagnosis with other infectious diseases including COVID-19. Clinically, the patients with MSF present the classic triad, fever, tache noir, and maculopapular rash in 40-50% of cases. In the absence of this typical clinical picture, the diagnosis could be challenging.

A small percentage of patients could present only the tache noir, which is generally pathognomonic of rickettsial diseases. However, clinical cases in which the tache noir was present in other zoonoses have been reported in the literature. [108] [109] [110] The presence of fever without other signs is, probably, the most difficult challenge for clinicians because it is the expression of many diseases, both infective (bacterial, viral, fungal, and parasitic) and not infective. In these patients, a proper anamnesis, laboratory findings, and radiological features are mandatory to permit the correct diagnosis. Blood cultures should be collected at the fever peak to exclude a bacterial or fungal infection. Furthermore, in the area where SARS-CoV-2 is circulating in the population, the nasopharyngeal swab, together with acute phase serology, is recommended to rule it out. Indeed, the common symptom in patients with COronaVIrus Disease (COVID-19) is the fever. 111, 112 The other symptoms that these two diseases have in common are headache, asthenia, and myalgia. The associations of dysgeusia, anosmia, and gastrointestinal symptoms could suggest the diagnosis of COVID-19. [113] [114] [115] The maculopapular rash is an expression of several diseases. 116 In these cases, clinicians should pay attention to the distribution, the pattern, and the relationship between the localization at the start of it and other clinical signs, especially the fever. Although respiratory symptoms are the most frequent in COVID-19, skin involvement should always be considered. Galván Casas C et al. 117 described the most common cutaneous pattern, and Magro et al. 118 demonstrated how SARS-CoV-2 is associated with microvascular damage and thrombosis.

Moreover, different cutaneous vasculitis-like patterns correlated with COVID-19 or SARS-CoV-2 therapy have been described. 119, 120 Diagnosis. Nowadays, the majority of reference laboratories in developed countries can provide quick identification of rickettsial pathogens thanks to molecular and serological assays. In many cases, the diagnosis could be made by the clinical manifestation, but the laboratory tests are necessary at the support of it.

The choice of the most appropriate diagnostic technique requires consideration of the suspected pathogen, the timing of symptoms onset, and the type of sample available for testing. 121 Serological tests remain essential diagnostic tools, 122 but Rickettsiae can be isolated from or detected in clinical specimens. The diagnostic tools available include serologic assays, molecular testing, cultures, immunochemistry, and Matrix-assisted laser desorption ionization-time of flight mass spectrometry (MALDI-TOF). 123 The diagnostic technique could be divided into two groups: 1) Diagnostic techniques used as routine.

Diagnostic techniques used as routine (Table 1) Serologic tests: Indirect immunofluorescence antibody assay (IFA) is a widely accepted serologic test for the detection of rickettsial infection. 124, 125 It is considered the most 

Indirect immunofluorescence antibody assay (IFA) Serologic High sensitivity and specificity for IgG [124, 125] .

Low sensibility for IgM; Operatordependent [129, 130] The enzyme-linked immunosorbent assay (ELISA) Serologic More sensitive than IFA for the detection of low antibodies level; Absorbance of the enzyme reaction is measured with a spectrophotometer [131, 132] .

Could be negative during the early phase [131, 132] .

Nucleic acid amplification tests (NAATs) (molecular methods)

Quick response; could be used during acute disease [123] ; provides the differentiation between different species [136] .

High costs; low sensitivity if used peripheral blood and serum [139] ; antibiotics reduce the sensitivity [116] . sensitive and specific method among serological assays. 126 IFA consists of rickettsial antigens fixed on a slide and detected by specific antibodies present in the patient's serum, which can be identified by a fluorescein-labeled conjugate. Serum of patients with clinical manifestation of disease must be collected on the day of the admission and 2-4 weeks after illness onset. 127 IFA assays are highly sensitive at detecting antibodies after 2-3 weeks after illness onset, and their results are best interpreted if serum samples collected in acute and convalescent phases are tested at the same time. 128 Most laboratories test for IgG antibodies because IgM antibodies reactive with Rickettsia rickettsii are frequently detected in patients with no other supportive evidence of a recent rickettsial infection. Therefore, the detection of IgM during the acute phase should not be considered diagnostic for an ongoing illness as there could be cross-reactivity with other species and persistence of IgM beyond acute status. 129, 130 The enzyme-linked immunosorbent assay (ELISA) detects the binding of specific antibodies to antigens in a serum sample. When secondary anti-human antibodies conjugated with an enzyme are bound to antibodies from a serum sample and subjected to a substrate, an enzymatic reaction will be measurable in a positive specimen. 131 ELISA is sensitive, reproducible, and allows the differentiation of IgG and IgM antibodies. The results are more sensitive than IFA for the detection of low antibodies level, such as during late convalescence. 121 ELISA has the advantage, compared to IFA, of eliminating the subjective evaluation since the absorbance of the enzyme reaction is measured with a spectrophotometer. The inhibition ELISA has been used only for the diagnosis of scrub typhus and seems to be more sensitive than IFA in the early phase of the disease. 132

These assays are more appropriate than serology in the diagnosis of acute infection; a sample collected early at disease onset, before the development of antibodies, is more likely to produce a positive result in PCR assays. When antibody production has increased to detectable levels, bacteria are rarely found in the bloodstream or at the inoculation site. Furthermore, if antibiotic treatment has been initiated, the sensitivity of PCR assays decreases for the same reason. 133, 134 The most used method is nucleic acid amplification tests (NAATs), such as PCR, which has acquired increasing importance over the past few years. The quick response allows a prompt diagnosis without the need to wait for seroconversion or cell culture's growth time, which can take from 10 to 30 days. 123 Amplification of species-specific DNA by PCR provides a useful method for the differentiation between the several Rickettsia spp. and to gain knowledge about the genomic differences within the genus. 124 The conventional PCR format, due to a large number of PCR products, is more prone to contamination. For this reason, a single-use primer PCR has been introduced. 135 Another molecular method is real-time PCR that offers the advantage of speed, reproducibility, quantitative capability, and reduced risk of contamination compared with conventional PCR assays. 136 Several clinical samples are suitable for PCR amplification: skin biopsy, eschar, swab, or CSF. Peripheral blood and serum could also be used, but PCR on these samples has a lower sensitivity compared to skin samples or eschar collected on the bite site. 137, 138 PCR detection of Rickettsia rickettsii in the blood is possible. Still, its sensitivity is lower because of the small numbers of rickettsiae in the blood in the first stages of the disease. 139 For this reason, during the acute phase, it is better to use the SFG tissue specimen. 116, 140 Doxycycline treatment decreases the sensitivity of PCR; therefore, obtaining blood before starting antibiotic therapy is recommended to minimize false-negative results. 116

Shell Vial:

This method requires a large number of bacteria and specific cell lines to proliferate, such as Vero E6 cells, human embryogenic lung fibroblast, and the promyelocytic HL-60 leukemia cell line (the most widely used cell line for growing A. 

Weil-Felix test Serologic Easy to use; low cost. It is still used in developed countries [125] .

Cross-reaction with other antigens. Low sensitivity, low sensibility [122, 168] Western Blot Serologic Highest sensitivity to early antibody, high specificity [144] .

Expensive, technically difficult to perform, longer procedure [144] .

Line Blot Serologic High specificity and sensitivity; a large number of antigens tested [121] .

No quantitative titers available; expensive [121] .

More sensitive than either the complement fixation or Weil-Felix [126] Rarely used, low sensitivity, long preparation [143] .

Rarely used for the high cost[145].

Hight sensitivity and specificity; tests multiple rickettsial antigens simultaneously [123] Cross-reactivity [123] ; high costs.

Serologic Very specific; used for seroepidemiologic studies [143] Poor sensitivity, especially during the early stage of the disease [126] Indirect immunoperoxidase assay (IPA) Serologic Similar to IFA; very sensitive and specific [143] Needs specific instrument and trained personal [143] Shell Vial Culture Highest specific; could be used during acute disease [121, 141] .

Long times [141] .; low success rate; needing specific cell lines [141] ; low sensitivity [142] Circulating endothelial cells (CECs) Other

Not influenced by previous antibiotic treatment; CECs level detected could be correlated with the severity of the disease [127] Low sensitivity; not easy to perform [146] .

High sensitivity [123, 143] Need bioptic sample, not easy to perform [123, 143] .

Early diagnoses, differentiation between species [123] High costs; not always available [123] . Only used to identify infections inside the arthropods [123, 147, 148] phagocytophilum). 141 Specimens for cell cultures should be collected before starting antibiotic treatment and should not be frozen. 121 To identify the cultivated small intracellular Rickettsiae, the laboratories should label bacteria by fluorescent antibodies or staining with the Gimenez method.

The low success rate and the complexity of this method do not permit the routinely use of this methodic. 142 Serologic methods:

The Weil-Felix test, based on the detection of immuneresponse to different Proteus antigens that cross respond with Rickettsia 125 should not be considered a first-line testing method anymore, even if it remains an option developing countries. It allows the detection of IgM antibodies 5-10 days after clinical manifestations. Western blot assay (WBA) was demonstrated to be more sensitive than IFA for the detection of early antibodies in Rickettsia spp. Nevertheless, it is generally more expensive and technically challenging to perform than other serological methods. 143 Furthermore, Rickettsia cultures are required. For these reasons, its use is limited to only a few reference laboratories. 144 The line, or dot, blot immunoassay, may be particularly useful for screening the many antigens that might be considered for patients with nonspecific or atypical clinical presentation. This test can be regarded as valuable only as a first-line test for the rapid diagnosis of acute cases in areas with high prevalence. 121 The microagglutination test could be divided into two different methods, which included the indirect hemagglutination test and the Latex agglutination method. The first one is specific for the detection of IgG and IgM for all Rickettsiae. 143 The Latex agglutination permitted the directed detection of the R. conorii, R. prowazekii, R. rickettsia, R. typhi, and infections. This method has a high sensitivity, but it is not routinely used for the high cost. 126, 145 Micro immunofluorescence (MIF) assay is similar to IFA except that wells are spotted with multiple rickettsial antigens for simultaneous detection. The negative aspect of this method is cross-reactivity, and its costs. 123 Complement Fixation (CF) test permitted the identification detection of antibodies specific for rickettsiae. It is peculiar, but it has shown a reduced sensitivity, especially during the early stage of the disease. For this reason, it is only used for seroepidemiological studies. 126 Indirect immunoperoxidase assay (IPA). The procedure is the same as IFA, but it used the peroxidase instead of fluorescein. It needs a specific instrument and trained personal. For this reason, it is not commonly used. 143 Other tests: Circulating endothelial cells (CECs) method allows the detection of R. conorii in circulating endothelial cells isolated from whole blood by using immunomagnetic beads coated with an endothelial cell-specific monoclonal antibody. 127 The sensitivity is about 50%, and it is not influenced by previous antibiotic treatment. Furthermore, the CECs level detected correlates with the severity of the infection, so it can be considered a prognostic indicator. 146 Immunohistochemistry (IHC) permits the Rickettsia's detection directly from biopsy specimens, but it could only be used during the acute phase and only if there is a rash or tache noir. 123, 143 The most recent diagnostic tool is the matrix-assisted laser desorption ionization-time of flight mass spectrometry (MALDI-TOF). This technique has been using with promise application for the Tick-borne infections inside the arthropods. 123 The future role of this new method could be applied to help the clinical decision. The identification of Rickettsiae inside the vector 147 or in the hemolymph 148 is showing great potential but remained a niche method. 123 Biosensors emerging technology allows the fast detection of Rickettsia-induced immune response. For example, the OmpA antigen, an outer membrane protein present in the R. rickettsia, the agent responsible for the spotted fever, allows the detection of anti-OmpA human IgG. This is possible through an amperometric immune-sensor by using a synthetic peptide, obtained from the H6PGA4 R. rickettsia protein, homologous to OmpA. 149 Treatment. Rickettsiae spp. are obligate intracellular bacteria; therefore, the standard treatment is based on tetracyclines or chloramphenicol. The gold standard therapy is indeed represented by doxycycline 100 mg per os twice daily x 7 days in adults and 2.2 mg/kg of body weight per dose twice daily, orally or intravenously. 140, 150 It has been demonstrated, in several studies, that doxycycline shortens the course of MSF and induces a rapid remission of symptoms. The problem is that tetracycline should be avoided in childhood, during pregnancy, 151, 152 in patients who are allergic to it, and in those who have a G6PDH deficiency. An alternative to doxycycline is chloramphenicol. It should be administered at a dosage of 50 mg/Kg/day in four doses for seven days. 56 Since 2000, chloramphenicol was used only for patients suffering from allergy, those having adverse effects to doxycycline or if fever persisted for more than five days or in those that relapsed after the therapy with tetracycline. However, chloramphenicol should also be avoided during pregnancy (grey baby syndrome), and because of the various adverse effects (aplastic anemia, bone marrow suppression), it is not recommended in children. Furthermore, in a randomized study on 415 children, the chloramphenicol group had a longer hospitalization. 56 For this reason, in pregnant women and children, the first choice is a macrolide. Different randomized studies have shown the macrolides' non-inferiority. In particular, Meloni et al., Bella et all and Cascio et al., in their randomized studies, have demonstrated the non-inferiority, respectively, of azithromycin, josamycin, and clarithromycin vs. doxycycline. [153] [154] [155] On the contrary, Munoz-Espin et al. have shown that erythromycin is less effective than doxycycline. 156 Studies in vitro have tested the efficacy of fluoroquinolones against Rickettsiae spp., showing encouraging results. 150, [157] [158] [159] Furthermore, randomized studies have shown that there is no difference between tetracycline and fluoroquinolones. [160] [161] [162] However, other studies found that fluoroquinolones are associated with increased MSF severity and the worst outcome. 163 Ciprofloxacin has been shown to have a deleterious effect on Rickettsia conorii-infected cells. 164 Rickettsiae spp. showed to be susceptible also to rifampicin, 165 but in 1991 a small trial showed its inferiority in comparison with doxycycline. 166 Even trimethoprim-sulfamethoxazole has been considered as a possible therapeutic option, but in vitro and in vivo studies have demonstrated that it is not active against Rickettsia spp. 150, 167 In the presence of unspecific symptoms during the spring to summer months, starting azithromycin seems reasonable given the ongoing COVID-19 epidemic in Mediterranean countries. 164 

Bergey's Manual of

Rickettsioses as paradigms of new or emerging infectious diseases

Ancestral Divergence of Rickettsia bellii from the Spotted Fever and Typhus Groups of Rickettsia and Antiquity of the Genus Rickettsia

Classification of Rickettsia tsutsugamushi in a new genus, Orientia gen. nov., as Orientia tsutsugamushi comb. nov

Reorganization of genera in the families Rickettsiaceae and Anaplasmataceae in the order Rickettsiales: Unification of some species of Ehrlichia with Anaplasma, Cowdria with Ehrlichia and Ehrlichia with Neorickettsia, descriptions of six new species combi

Paradoxical evolution of rickettsial genomes

Rickettsia phylogenomics: Unwinding the intricacies of obligate intracellular life

New approaches in the systematics of rickettsiae

Genomes of the most dangerous epidemic bacteria have a virulence repertoire characterized by fewer genes but more toxin-antitoxin modules

Massive comparative genomic analysis reveals convergent evolution of specialized bacteria

The Genome Sequence of Rickettsia felis Identifies the First Putative Conjugative Plasmid in an Obligate Intracellular Parasite

Similarities and Differences in Host Cell Signaling following Infection with Different Rickettsia Species

Role of T lymphocyte subsets in immunity to spotted fever group Rickettsiae

New insight into immunity and immunopathology of Rickettsial diseases

Tick-borne rickettsioses around the world: Emerging diseases challenging old concepts

Deciphering the Relationships between Rickettsia conorii conorii and Rhipicephalus sanguineus in the Ecology and Epidemiology of Mediterranean Spotted Fever

Warmer weather linked to tick attack and emergence of severe Rickettsioses

Update on tick-borne rickettsioses around the world: A geographic approach

Genome sequence of Rickettsia conorii subsp. israelensis, the agent of israeli spotted fever

Co-feeding as a route for transmission of Rickettsia conorii israelensis between Rhipicephalus sanguineus ticks

Fatal case of Israeli spotted fever after Mediterranean cruise

The Presence of Eschars, but Not Greater Severity, in Portuguese Patients Infected with Israeli Spotted Fever

Presence of Rickettsia conorii subsp. israelensis, the causative agent of Israeli spotted fever

Israeli spotted fever

Spotted Fever Group Rickettsiae in Ticks in Cyprus

Tick-borne zoonotic bacteria in ticks collected from central Spain

Clustered cases of rickettsia sibirica mongolitimonae infection

Simultaneous detection of "Rickettsia mongolotimonae" in a patient and in a tick in Greece

Rickettsia sibirica isolation from a patient and detection in ticks

A new spotted-fever-group rickettsiosis

Rickettsia sibirica mongolitimonae infection

Rickettsia sibirica mongolitimonae infection, Turkey

Human infection with rickettsia sibirica mongolitimonae, Spain

Rickettsia sibirica mongolitimonae in traveler from Egypt

Spotted Fever Group Rickettsiae in Ticks Feeding on Humans in Northwestern Spain: Is Rickettsia conorii Vanishing

Rickettsia slovaca and Rickettsia raoultii in Dermacentor marginatus and Dermacentor reticulatus ticks from Slovak Republic

Typhus and other rickettsioses -Emerging infections in Germany

Coinfections of Rickettsia slovaca and Rickettsia helvetica with Borrelia lusitaniae in ticks collected in a Safari Park

Rickettsia conorii israelensis in Rhipicephalus sanguineus ticks

First detection of Rickettsia slovaca in Greece

ticks

Tick-borne lymphadenopathy -a new rickettsial disease?

Rickettsia slovaca Infection: DEBONEL/TIBOLA

Rickettsia slovaca in Dermacentor marginatus and tick-borne lymphadenopathy

A case of tick-transmitted lymphadenopathy in Bulgaria associated with Rickettsia slovaca

Rickettsia slovaca infection, France. Emerg Infect Dis

Tick-borne lymphadenopathy (TIBOLA) acquired in Southwestern Germany

Rickettsia slovaca and R. raoultii in Tick-borne Rickettsioses

Evaluation of clinical specimens for Rickettsia, Bartonella, Borrelia, Coxiella, Anaplasma, Franciscella and Diplorickettsia positivity using serological and molecular biology methods

Rickettsia helvetica in patient with meningitis

Mediterranean spotted fever rickettsiosis in Italy

Seroepidemiological study of Rickettsia felis, Rickettsia typhi, and Rickettsia conorii infection among the population of southern Spain

Mediterranean spotted fever: case series of 24 years (1989-2012)

Mediterranean spotted fever-like illness in Sardinia, Italy: a clinical and microbiological study

Mediterranean spotted fever: clinical and laboratory characteristics of 415 Sicilian children

A case of Mediterranean spotted fever associated with severe respiratory distress syndrome

Coronary involvement in Mediterranean spotted fever

Myocarditis in Mediterranean spotted fever: a case report and a review of the literature

Mediterranean spotted fever presenting as acute leucocytoclastic vasculitis

Retinopathy in Rickettsia conorii infection: Case report in an immunocompetent host

Retinal Manifestations of Mediterranean Spotted Fever

A rare case of retinal artery occlusion in the context of mediterranean spotted fever

Posterior segment manifestations of Rickettsia conorii infection

A case series of spotted fever rickettsiosis with neurological manifestations in Sri Lanka

Severe case of Mediterranean spotted fever in Greece with predominantly neurological features

Mediterranean spotted fever and hearing impairment: A rare complication

Sensorineural hearing loss complicating severe rickettsial diseases: Report of two cases

Guillain -Barré Polyneuropathy Associated with Mediterranean Spotted Fever: Case Report

A case of acute quadriplegia complicating Mediterranean spotted fever

Mediterranean spotted fever and encephalitis: A case report and review of the literature

Mediterranean spotted fever with encephalitis

Rickettsial Meningitis and Encephalitis

Rickettsial meningitis

Mediterranean spotted fever presenting as an acute pancreatitis

Splenic rupture and malignant Mediterranean spotted fever

Secondary hemophagocytic lymphohistiocytosis in zoonoses. A systematic review

Unusual pancytopenia secondary to haemophagocytosis syndrome in rickettsioses

Haemophagocytic syndrome and rickettsial diseases

Arthritis in Mediterranean spotted fever

Arthritis in mediterranean spotted fever. an immune complex mediated synovitis

Guidelines for the diagnosis of tick-borne bacterial diseases in Europe

Questions on Mediterranean spotted fever a century after its discovery

Mediterranean spotted fever in Portugal: risk factors for fatal outcome in 105 hospitalized patients

Mediterranean spotted fever in Spain, 1997-2014: Epidemiological situation based on hospitalization records

Scalp Eschar and Neck Lymphadenopathy Caused by Bartonella henselae after Tick Bite

Tick-borne lymphadenopathy (TIBOLA)

Spotless Rickettsiosis Caused by Rickettsia slovaca and Associated with Dermacentor Ticks

Lymphangitis-Associated Rickettsiosis, a New Rickettsiosis Caused by Rickettsia sibirica mongolotimonae: Seven New Cases and Review of the Literature

Rickettsia sibirica subsp. mongolitimonae infection and retinal vasculitis

& Sotto A. A case of severe sepsis with disseminated intravascular coagulation during Rickettsia sibirica mongolitimonae infection

Acute myopericarditis associated with tickborne Rickettsia sibirica mongolitimonae

Real-time PCR for early diagnosis of Rickettsia conorii and prompt management in patients with septic shock and multiple organ failure: two case reports

Septic shock in a patient infected with Rickettsia sibirica mongolitimonae

Urban family cluster of spotted fever rickettsiosis linked to Rhipicephalus sanguineus infected with Rickettsia conorii subsp. caspia and Rickettsia massiliae

Studies of a "new" rickettsiosis "Astrakhan" spotted fever

Report of eight cases of fatal and severe Mediterranean spotted fever in Portugal

Israeli Spotted Fever in Sicily. Description of two cases and minireview

Rickettsia monacensis as Cause of Mediterranean Spotted Fever-like Illness

Rickettsia monacensis and human disease

Case report: A patient from Argentina infected with Rickettsia massiliae

Rickettsia massiliae in the Canary Islands

On Behalf Of The Internal, Medicine Sepsis Study Group. Human Rickettsia aeschlimannii infection: first case with acute hepatitis and review of the literature

First direct detection of rickettsial pathogens and a new rickettsia

Septicaemia with Rickettsia helvetica in a patient with acute febrile illness, rash and myasthenia

Evidence of Rickettsia helvetica infection in humans, eastern France

Tache Noire in a Patient with Acute Q Fever

A novel zoonotic Anaplasma species is prevalent in small ruminants: potential public health implications. Parasites and Vectors

From Q fever to Coxiella burnetii infection: A paradigm change

Epidemiology and clinical features of COVID-19: A review of current literature

Clinical features, laboratory findings and predictors of death in hospitalized patients with COVID-19 in Sardinia, Italy

Clinical Characteristics of Coronavirus Disease 2019 in China

Objective evaluation of anosmia and ageusia in COVID -19 patients: a single -center experience on 72 cases

Olfactory and gustatory function impairment in COVID-19 patients: Italian objective multicenter-study

Tickborne Rickettsial Diseases Working Group, CDC. Diagnosis and management of tick-borne rickettsial diseases: Rocky Mountain spotted fever, ehrlichioses, and anaplasmosis--United States: a practical guide for physicians and other health-care and public health professionals

Complement associated microvascular injury and thrombosis in the pathogenesis of severe COVID-19 infection: A report of five cases

Updated approaches against SARS-CoV-2

Vascular skin symptoms in COVID-19: a french observational study

Laboratory diagnosis of Rickettsioses: Current approaches to diagnosis of old and new Rickettsial diseases

Rickettsial diseases and their serological diagnosis

A concise review of the epidemiology and diagnostics of rickettsioses: Rickettsia and orientia spp

Manual of Clinical Microbiology

Ehrlichia, Anaplasma, and Related Intracellular Bacteria

A comparison of the complement fixation, indirect fluorescent antibody, and microagglutination tests for the serological diagnosis of rickettsial diseases

Diagnosis of mediterranean spotted fever by indirect immunofluorescence of rickettsia conorii in circulating endothelial cells isolated with monoclonal antibody-coated immunomagnetic beads

Serodiagnosis of Rocky Mountain spotted fever: Comparison of IgM and IgG enzyme-linked immunosorbent assays and indirect fluorescent antibody test

Inter-and intralaboratory comparison of Ehrlichia equi and human granulocytic ehrlichiosis (HGE) agent strains www.mjhid.org

for serodiagnosis of HGE by the immunofluorescent-antibody test

Diagnosis of granulocytic ehrlichiosis in humans by immunofluorescence assay

Enzyme-linked immunosorbent assay (ELISA) quantitative assay of immunoglobulin G

Use of monoclonal antibodies against Rickettsia tsutsugamushi Kawasaki for serodiagnosis by enzyme-linked immunosorbent assay

Short report: Detection of rickettsioses and Q fever in Sri Lanka

Two human cases of Rickettsia felis infection

Suicide PCR on skin biopsy specimens for diagnosis of Rickettsioses

State of the art of diagnosis of rickettsial diseases: The use of blood specimens for diagnosis of scrub typhus, spotted fever group rickettsiosis, and murine typhus

Comparison of Two Quantitative Real Time PCR Assays for Rickettsia Detection in Patients from Tunisia

Evaluation of serological tests for the diagnosis of rickettsiosis in Denmark

Correlation of Rickettsial Titers, Circulating Endotoxin, and Clinical Features in Rocky Mountain Spotted Fever

Diagnosis and management of tick-borne rickettsial diseases: Rocky mountain spotted fever and other spotted fever group rickettsioses, ehrlichioses, and anaplasmosis -United States a practical guide for health care and public health professionals

Perspectivas sobre el diagnóstico de laboratorio de enfermedades rickettsiales en el siglo 21

Studies of Spotted Fever Rickettsia -Distribution, Detection, Diagnosis and Clinical Context. 2016. 1-78 p

Laboratory diagnosis of rickettsial infections

Diagnostic strategy of rickettsioses and ehrlichioses

Indirect hemagglutination test for detection of antibody to Rickettsia rickettsii in sera from humans and common laboratory animals

Demonstration of Rickettsia conorii-induced endothelial injury in vivo by measuring circulating endothelial cells, thrombomodulin, and von Willebrand factor in patients with Mediterranean spotted fever

Detection of Rickettsia spp in Ticks by

Identification of tick species and disseminate pathogen using hemolymph by MALDI-TOF MS

Development of an electrochemical immunosensor for the diagnostic testing of spotted fever using synthetic peptides

In vitro susceptibilities of 27 rickettsiae to 13 antimicrobials

The tetracyclines

Transplacental Effect of Tetracyclines on Teeth

Azithromycin vs. doxycycline for Mediterranean spotted fever

Randomized trial of doxycycline versus josamycin for Mediterranean spotted fever

Efficacy and Safety of Clarithromycin as Treatment for Mediterranean Spotted Fever in Children: A Randomized Controlled Trial

Erythromycin versus tetracycline for treatment of mediterranean spotted fever

In vitro susceptibility of Rickettsia conorii to ciprofloxacin as determined by suppressing lethality in chicken embryos and by plaque assay

Susceptibility of rickettsia conorii and r. Rickettsii to pefloxacin, in vitro and in ovo

Susceptibility of Rickettsia conorii, R. rickettsii, and Coxiella burnetii to PD 127,391, PD 131,628, www.mjhid.org

Evaluation of ciprofloxacin and doxycycline in the treatment of mediterranean spotted fever

Randomized double-blind evaluation of ciprofloxacin and doxycycline for Mediterranean spotted fever

Ciprofloxacin therapy for Mediterranean spotted fever

Analysis of risk factors for malignant mediterranean spotted fever indicates that fluoroquinolone treatment has a deleterious effect

Deleterious effect of ciprofloxacin on Rickettsia conorii-infected cells is linked to toxinantitoxin module up-regulation

Antibiotic susceptibility of Rickettsia and treatment of rickettsioses

Randomized trial of 5-day rifampin versus 1-day doxycycline therapy for mediterranean spotted fever

Deleterious effect of trimethoprimsulfamethoxazole in Mediterranean spotted fever

The antigenic relationship between bacillus proteus x-19 and rickettsiae: III. a study of the antigenic composition of the extracts of bacillus proteus x-19