DEBONEL/TIBOLA: Is Rickettsia slovaca the Only Etiological Agent?

Epidemiological, Clinical, and Microbiological Characteristics in a Large Series of Patients Affected by Dermacentor-Borne-Necrosis-Erythema-Lymphadenopathy from a Unique Centre from Spain

During recent decades, a tick-borne rickettsial syndrome, characterized by eschar and painful lymphadenopathy after Dermacentor marginatus-bite, has been described as an emerging rickettsiosis in Europe. Our group named it DEBONEL (Dermacentor-borne-necrosis-erythema-lymphadenopathy), regarding the vector and the main infection signs. Other groups called it TIBOLA (tick-borne-lymphadenophathy) and, later, SENLAT (scalp-eschar-and-neck-lymphadenopathy-after-tick-bite), expanding, in the latter, the etiological spectrum to other pathogens. Objective: To investigate the etiology of DEBONEL agents in our area, and to compare their epidemiological/clinical/microbiological characteristics. During 2001-2020, 216 patients clinically diagnosed of DEBONEL (the largest series from one center) in La Rioja (northern Spain) were examined. Rickettsia spp. were amplified in 14/104 (13.46%) blood samples, 69/142 (48.59%) eschar swabs, 7/7 (100%) biopsies, and 71/71 (100%) D. marginatus from patients. For samples in which Rickettsia was undetected, no other microorganisms were found. 'Candidatus Rickettsia rioja', Rickettsia slovaca, Rickettsia raoultii, and Rickettsia DmS1 genotype were detected in 91, 66, 4, and 3 patients, respectively. DEBONEL should be considered in patients with clinical manifestations herein described in areas associated to Dermacentor. The most frequently involved agent in our environment is 'Ca. R. rioja'. The finding of Rickettsia sp. DmS1 in ticks attached to DEBONEL patients suggests the implication of other rickettsia genotypes.

The Unexpected Holiday Souvenir: The Public Health Risk to UK Travellers from Ticks Acquired Overseas

Overseas travel to regions where ticks are found can increase travellers' exposure to ticks and pathogens that may be unfamiliar to medical professionals in their home countries. Previous studies have detailed non-native tick species removed from recently returned travellers, occasionally leading to travel-associated human cases of exotic tick-borne disease. There are 20 species of tick endemic to the UK, yet UK travellers can be exposed to many other non-native species whilst overseas. Here, we report ticks received by Public Health England's Tick Surveillance Scheme from humans with recent travel history between January 2006 and December 2018. Altogether, 16 tick species were received from people who had recently travelled overseas. Confirmed imports (acquired outside of the UK) were received from people who recently travelled to 22 countries. Possible imports (acquired abroad or within the UK) were received from people who had recently travelled to eight European countries. Species-specific literature reviews highlighted nine of the sixteen tick species are known to vector at least one tick-borne pathogen to humans in the country of acquisition, suggesting travellers exposed to ticks may be at risk of being bitten by a species that is a known vector, with implications for novel tick-borne disease transmission to travellers.

Prevalence and molecular characterization of Rickettsia spp. in questing ticks from north-western Spain

Tick-borne rickettsioses, most of them belonging to the spotted fever group (SFG), have been recognized as important emerging vector-borne zoonotic diseases. In order to determine the presence of Rickettsia spp. in questing ticks from north-western Spain, 1056 Ixodes ricinus, 19 Dermacentor marginatus, 17 Dermacentor reticulatus and one Ixodes acuminatus were processed. Rickettsia DNA was detected by PCR targeting rOmpA and rOmpB genes. A total of 219 (20.7%) I. ricinus, 19 (100%) D. marginatus and four D. reticulatus (23.5%) were positive. The prevalence was significantly higher in I. ricinus from coastal areas and in winter. Five species were identified: Rickettsia felis, Rickettsia monacensis, Rickettsia raoultii, Rickettsia slovaca and "Candidatus Rickettsia rioja". Our results reveal a significant presence of some pathogenic Rickettsia species in questing tick populations from this area which involves a noticeable risk of rickettsiosis. As R. raoultii, R. slovaca and "Ca. R. rioja" DNA were identified in I. ricinus, considered an unusual vector for these Rickettsia species, further studies are needed to unravel the role of that tick species in the maintenance and transmission of these three Rickettsia species in north-western Spain.

Rickettsial infections of the central nervous system

As a result of migrations and globalization, people may face a possible increase in the incidence of central nervous system rickettsial infections (CNS R). These diseases, caused by Rickettsia species and transmitted to humans by arthropod bites, are putatively lethal. However, the diagnosis of CNS R is challenging and often delayed due to their nonspecific clinical presentation and the strict intracellular nature of rickettsiae. Furthermore, transfer of rickettsiae to the brain parenchyma is not yet understood. The aim of this review is to analyze and summarize the features and correlated findings of CNS R in order to focus attention on these intriguing but frequently neglected illnesses. We also incorporated data on CNS infections caused by Rickettsia-related microorganisms.

Tick-borne lymphadenopathy, an emerging disease

Tick-borne lymphadenopathy (TIBOLA) is a spotted fever group disease characterized by an eschar and pronounced enlarged lymph nodes after a scalp tick bite. The goal of this synopsis is to review the TIBOLA literature published until May 2013: Forty-one articles (reporting 537 cases) were included. There was a predominance of cases in females and young people. Spain, France, and Hungary reported the majority of cases, and they were mainly reported in the colder seasons. The involved tick bite was frequently on the scalp. Rickettsia slovaca was the most frequent identified bacterium and Dermacentor marginatus the most frequently identified vector. The most prescribed antibiotic was doxycycline. TIBOLA has the potential to emerge outside Europe: improving knowledge of TIBOLA may promote early symptoms recognition and may allow early treatment.

Old and new tick-borne rickettsioses

The field of rickettsiology is rapidly evolving. Rickettsiae are small Gram-negative bacteria that can be transmitted to humans by arthropods. In most cases they are transmitted transovarially in the arthropod; human beings are incidental hosts. In recent years the use of cell culture and molecular biology has profoundly changed our knowledge of rickettsiae and has led to the description of several new species. New rickettsial diseases have been found in three main situations: firstly, in places where no new species have been identified, typical rickettsial symptoms have been observed (Japan, China); secondly, typical rickettsioses have been found to be caused by different organisms - in such cases a new Rickettsia species has been misdiagnosed as a previously identified bacterium (for example, R. parkeri was confused with R. rickettsii); thirdly, atypical clinical symptoms have been found to be caused by rickettsial organisms such as R. slovaca. These findings challenge the old dogma that only one tick-borne rickettsiosis is prevalent in one geographical area. Many Rickettsia spp. have been identified in ticks, but have not yet been implicated in human pathology. These rickettsiae should be considered as potential pathogens. All known or suspected rickettsial diseases should be treated (including in children) with doxycycline.

Tick-borne rickettsioses in Europe

Rickettsioses are caused by obligate intracellular bacteria within the genus Rickettsia, mainly transmitted by arthropods. Until recently, Mediterranean spotted fever (MSF) caused by Rickettsia conorii was considered the only tick-borne rickettsiosis in Europe. However, 'new' TBR have been described in Europe during last years. For instance, other subspecies such as R. conorii caspia and R. conorii israelensis have been involved in MSF. Dermacentor-borne necrosis erythema and lymphadenopathy/tick-borne lymphadenopathy (DEBONEL/TIBOLA) cases caused by Rickettsia slovaca, Rickettsia raoultii, and Rickettsia rioja been described in several countries where Dermacentor marginatus ticks (the mainly implicated vector) are present. Rickettsia helvetica has also been involved as a human pathogen in cases of fever with and without rash and in patients with meningitis and carditis. Other TBR such as lymphangitis-associated rickettsioses (LAR), caused by Rickettsia sibirica mongolitimonae, have been diagnosed in different European countries (France, Spain, Portugal and Greece). Rickettsia massiliae is considered an etiological agent of MSF-like illness in the Mediterranean basin. Furthermore, Rickettsia monacensis that is distributed all along Europe has been isolated from patients with MSF-like illness in Spain. Although Rickettsia aeschlimannii has been associated with MSF-like in Africa and is distributed in the Mediterranean area, no autochthonous human cases have been reported for Europe. Other Rickettsia species detected in ticks and unrelated to human disease (Candidatus Rickettsia kotlanii, Candidatus Rickettsia barbariae, Candidatus Rickettsia vini) could be potentially involved in the next years. Climate changes, among other factors, may contribute to the emergence of other rickettsioses or change their distribution. Lastly, African tick-bite fever (ATBF), caused by Rickettsia africae, is frequently diagnosed in Europe in patients returning from endemic areas.

Usefulness of rickettsial PCR assays for the molecular diagnosis of human rickettsioses

BACKGROUND

The effectiveness of PCR methods to amplify rickettsiae from clinical samples has still not been evaluated. Our aim was to determine the sensitivity and usefulness for Rickettsia species identification by PCR methods, targeting 16S rDNA, htrA, gltA, ompA, and ompB genes for molecular diagnosis of rickettsioses.

METHODS

A total of 72 clinical samples (EDTA-blood, skin biopsies and ticks) taken from 52 patients in the early phase of the illness with PCR-confirmed rickettsioses were included. Single [16S rDNA, gltA (5' end), and htrA genes] and sequential (nested or semi-nested) PCR assays [ompB, gltA (central region) and ompA genes] were performed.

RESULTS

For single-stage PCR assays, the greatest sensitivity (33.3%) was obtained using the gltA (5' end), while for sequential assays, the most sensitive results were obtained using the ompB assay (83.3%). The highest sensitivity (100%) was achieved using the three sequential PCRs. The ompA PCR method was the most reliable for identifying Rickettsia species, according to clinical features.

CONCLUSIONS

PCR-based amplification methods are useful rickettsial diagnostic tools in the early phase of the illness. The three sequential PCR assays here investigated (ompB, gltA and ompA) appear to be useful tools for molecular diagnosis of rickettsioses. ompB PCR assay is effective for primary screening, since it detects a high percentage of positive samples. ompA assay is the most useful method to identify a Rickettsia species in human pathology. Nevertheless, epidemiology, clinical symptoms and the vector involved in the infection have to be taken into account for the diagnosis of rickettsioses.

Rickettsia slovaca and R. raoultii in tick-borne Rickettsioses

Tick-borne lymphadenopathy (TIBOLA), also called Dermacentor-borne necrosis erythema and lymphadenopathy (DEBONEL), is defined as the association of a tick bite, an inoculation eschar on the scalp, and cervical adenopathies. We identified the etiologic agent for 65% of 86 patients with TIBOLA/DEBONEL as either Rickettsia slovaca (49/86, 57%) or R. raoultii (7/86, 8%).

Diagnosis and treatment of tick infestation and tick-borne diseases with cutaneous manifestations

Hard and soft ticks may be associated directly or indirectly with a number of dermatoses, both infectious and inflammatory in origin. Morbidity may occur as a result of tick bites, tick toxicosis, and even infestation. These arthropod vectors may transmit life-threatening protozoan, bacterial, rickettsial, and viral diseases with systemic and cutaneous findings. Additionally, ticks may transmit more than one pathogen with subsequent human coinfection. This article reviews the presentation of tick-borne illnesses and the medical management of these diseases. Among others, diseases such as ehrlichiosis, anaplasmosis, babesiosis, tularemia, borrelioses, tick-borne encephalitides, rickettsial spotted fevers, and tick typhus are discussed in this article. The recognition of skin manifestations associated with these diseases is paramount to early diagnosis and treatment initiation.

Detection of Rickettsia spp. in Haemaphysalis ticks collected in La Rioja, Spain

In an attempt to know the potential risk of human disease after exposure to ticks in La Rioja (North of Spain), the objective of our study was to investigate the presence of Rickettsia species in Haemaphysalis ticks collected in our area. A total of 177 Haemaphysalis spp. belonging to three species (H. punctata, H. sulcata, and H. inermis) were subjected to DNA extraction and tested by polymerase chain reaction (PCR) targeting three rickettsial genes: gltA, ompB, and ompA. Six (3 H. inermis, 2 H. punctata, and 1 H. sulcata) of the 177 specimens were found to be infected (3.4%). The rickettsiae in H. inermis ticks (n = 3) were identified as Rickettsia aeschlimannii by sequencing of the genes coding for gltA, ompB, and ompA. Nucleotide sequences from H. punctata and H. sulcata samples that yielded PCR products (n = 3), showed >99% similarity with sequences of Rickettsia endosymbiont of H. sulcata and 'Candidatus Rickettsia hoogstraalii' for gltA and ompB genes, respectively. Attempts to amplify ompA from these two H. punctata and one H. sulcata failed. This study suggests that H. inermis could be a vector for tick-borne spotted fever caused by R. aeschlimannii in the north of Spain. Further studies on characterization and culture of rickettsial endosymbionts found in Haemaphysalis spp. should be performed.

Rickettsial Diseases in Russia

Currently, several rickettsioses are officially being reported in the Russian Federation. These are epidemic typhus and Brill-Zinsser disease, both caused by Rickettsia prowazekii which has a historic prevalence in Russia. Nowadays only single sporadic cases of R. prowazekii infection are reported. The last significant outbreak occurred in 1997 in a mental nursing home, where 29 cases were identified. Registered morbidity of typhus in Russia varies from 0 to 0.01 per thousand for the last decade. Siberian tick typhus, caused by R. sibirica, is registered on a large territory from Pacific coasts to Western Siberia, and its incidence continuously increases, varying between 2.5 and 4.0 thousand officially registered cases per year. Astrakhan spotted fever, caused by R. conorii subsp. caspia has been recognized since 1983. Recently, Far Eastern tick-borne rickettsiosis, caused by R. heilongjiangensis, has been described. Several other pathogenic spotted fever group rickettsiae have been detected and isolated from ticks in Russia; however, they have not yet been linked with clinical cases in these regions.