Newly Recognized Spotted Fever Group Rickettsia as Cause of Severe Rocky Mountain Spotted Fever-Like Illness, Northern California, USA.

The incidence of spotted fever group (SFG) rickettsioses in the United States has tripled since 2010. Rocky Mountain spotted fever, the most severe SFG rickettsiosis, is caused by Rickettsia rickettsii. The lack of species-specific confirmatory testing obfuscates the relative contribution of R. rickettsii and other SFG Rickettsia to this increase. We report a newly recognized rickettsial pathogen, Rickettsia sp. CA6269, as the cause of severe Rocky Mountain spotted fever-like illness in 2 case-patients residing in northern California. Multilocus sequence typing supported the recognition of this pathogen as a novel Rickettsia genotype most closely related to R. rickettsii. Cross-reactivity observed for an established molecular diagnostic test indicated that Rickettsia sp. CA6269 might be misidentified as R. rickettsii. We developed a Rickettsia sp. CA6269-specific real-time PCR to help resolve this diagnostic challenge and better characterize the spectrum of clinical disease and ecologic epidemiology of this pathogen.

Rocky Mountain Spotted Fever Mimicking Multisystem Inflammatory Syndrome in Hospitalized Children, Sonora, Mexico.

We describe 5 children who had Rocky Mountain spotted fever (RMSF) and manifested clinical symptoms similar to multisystem inflammatory syndrome in Sonora, Mexico, where RMSF is hyperendemic. Physicians should consider RMSF in differential diagnoses of hospitalized patients with multisystem inflammatory syndrome to prevent illness and death caused by rickettsial disease.

Discovery of a novel spotted fever group Rickettsia, "Candidatus Rickettsia kedanie," in unfed larval chigger mites, Leptotrombidium scutellare.

Spotted fever group (SFG) rickettsia, the causative agent of SFG rickettsiosis, is predominantly carried by ticks, whereas Orientia tsutusgamushi, the causative agent of scrub typhus, is primarily transmitted by chigger mites in Japan. In this study, we attempted to isolate intracellular eubacteria from Leptotrombidium scutellare, a major vector of O. tsutsugamushi; moreover, we isolated an SFG rickettsia using a mosquito-derived cell line. Draft genome sequences of this unique isolate, by applying criteria for species delimitation, classified this isolate as a novel strain, proposed as "Rickettsia kedanie." Further genetic analysis identified conserved virulence factors, and the isolate successfully propagated in mammalian cells, suggesting its ability to cause diseases in humans. The presence of SFG rickettsia in unfed larvae implies potential dual-pathogen carriage and reflects a symbiotic relationship similar to that between the mites and O. tsutsugamushi, indicating possibility of its transovarial transmission from female adults. Furthermore, conserved genomic similarity of the novel isolate to known SFG rickettsia suggests potential multiple hosts, including chiggers and ticks. In the natural environment, ticks, chigger mites, and wild animals may carry new isolates, complicating the infection cycle and increasing the transmission risks to humans. This discovery challenges the conventional association of SFG rickettsia with ticks, emphasizing its implications for research and disease control. However, this study was confined to a particular species of chigger mites and geographic area, underscoring the necessity for additional studies to comprehend the ecological dynamics, host interactions, and health implications linked to this newly identified SFG rickettsia.

Rickettsia conorii subsp. israelensis infection in a pediatric patient presenting skin rash and abdominal pain: a case report from Southeast Iran.

BACKGROUND: The healthcare system in Iran appears to overlook Mediterranean spotted fever (MSF) as an endemic disease, particularly in pediatric cases, indicating the need for greater attention and awareness. CASE PRESENTATION: A six-year-old patient with fever, abdominal pain, headache, skin rashes, diarrhea, vomiting, and black eschar (tache noire) from southeast Iran was identified as a rickettsiosis caused by Rickettsia conorii subsp. israelensis through clinical and laboratory assessments, including IFA and real-time PCR. The patient was successfully treated with doxycycline. CONCLUSIONS: Symptoms like rash, edema, eschar, and abdominal pain may indicate the possibility of MSF during the assessment of acute febrile illness, IFA and real-time PCR are the primary diagnostic methods for this disease.

Gaps and inconsistencies in the current knowledge and implementation of biosafety and biosecurity practices for rickettsial pathogens.

INTRODUCTION: Rickettsia spp. and Orientia spp. are the causes of neglected infections that can lead to severe febrile and systemic illnesses in humans. Implementing proper biosafety practices when handling these pathogens is crucial to ensure a safe and sustainable work environment. It is essential to assess the current knowledge and identify any potential gaps to develop effective measures that minimise the risk of exposure to these pathogens. By doing so, we can establish a comprehensive framework that promotes safety, mitigates hazards, and safeguards the well-being of personnel and the surrounding community. METHODS AND RESULTS: This review aimed to synthesise and determine the evidence base for biosafety precautions for Rickettsia spp. and Orientia spp. pathogens. Enhancing our understanding of the relative infectious risk associated with different strains of Rickettsia and Orientia spp. requires identifying the infectious dose of these pathogens that can cause human disease. The application of risk groups for Rickettsia and Orientia spp. is inconsistent across jurisdictions. There is also incomplete evidence regarding decontamination methods for these pathogens. With regards to Orientia spp. most of the available information is derived from experiments conducted with Rickettsia spp. CONCLUSIONS: Rickettsia and Orientia spp. are neglected diseases, as demonstrated by the lack of evidence-based and specific biosafety information about these pathogens. In the case of Orientia spp., most of the available information is derived from Rickettsia spp., which may not be appropriate and overstate the risks of working with this pathogen. The advent of effective antibiotic therapy and a better understanding of the true hazards and risks associated with pathogen manipulation should inform decisions, allowing a sustainable and safe work environment.

Evidence on the prevalence of emerging and re-emerging tick- and flea-borne rickettsial agents in acute encephalitis syndrome endemic areas of northeast Uttar Pradesh, India.

Outbreaks of acute encephalitis syndrome (AES) with unknown aetiology are reported every year in Gorakhpur district, Uttar Pradesh, India, and Orientia tsutsugamushi, the rickettsial pathogen, responsible for scrub typhus has been attributed as the primary cause of AES problem. However, information on the prevalence of other rickettsial infections is lacking. Hence, this study was carried out to assess any occurrence of tick- and flea-borne rickettsial agents in villages reporting AES cases in this district. In total, 825 peridomestic small mammals were trapped, by setting 9254 Sherman traps in four villages with a trap success rate of 8.9%. The Asian house shrew, Suncus murinus, constituted the predominant animal species (56.2%) and contributed to the maximum number (87.37%) of ectoparasites. In total, 1552 ectoparasites comprising two species of ticks and one species each of flea and louse were retrieved from the trapped rodents/shrews. Rhipicephalus sanguineus, the brown dog tick, was the predominant species retrieved from the trapped rodents/shrews, and the overall infestation rate was 1.75 per animal. In total, 4428 ectoparasites comprising five tick species, three louse species and one flea species were collected from 1798 domestic animals screened. Rhipicephalus microplus was the predominant tick species collected from the domestic animals. The cat flea, Ctenocephalides felis, constituted 1.5% of the total ectoparasites. Of all the ectoparasite samples (5980) from domestic animals and rodents, tested as 1211 pools through real-time PCR assays, 64 pools were positive for 23S rRNA gene of rickettsial agents. The PCR-positive samples were subjected to multi-locus sequence typing (MLST). In BLAST and phylogenetic analysis, the ectoparasites were found to harbour Rickettsia asembonensis (n = 9), Rickettsia conorii (n = 3), Rickettsia massiliae (n = 29) and Candidatus Rickettsia senegalensis (n = 1). A total of 22 pools were detected to have multiple rickettsial agents. The prevalence of fleas and high abundance of tick vectors with natural infections of rickettsial agents indicates the risk of transmission of tick- and flea-borne rickettsial diseases in rural villages of Gorakhpur. Further epidemiological studies are required to confirm the transmission of these agents to humans.

Distribution of ticks and their possession of spotted fever group Rickettsia in Ibaraki prefecture.

INTRODUCTION: Tick-borne diseases (TBDs) are a growing threat in Japan. However, distribution of ticks and their possession of human pathogens remain poorly understood. METHODS: In the present study, we collected 3477 ticks at 6 remote, woodland sites in Ibaraki prefecture between May 23 and November 4, 2021, and investigated the distribution and the possession of spotted fever group Rickettia (SFGR). RESULTS: The collected ticks included Haemaphysalis flava (78.3 %), Haemaphysalis longicornis (9.0 %), Haemaphysalis hystricis (4.6 %), Ixodes turdus (4.3 %), Amblyomma testudinarium (2.1 %), Haemaphysalis cornigera (0.9 %), Haemaphysalis formosensis (0.9 %), Haemaphysalis megaspinosa (0.2 %), Ixodes ovatus (0.1 %), Ixodes nipponensis (0.09 %), and Ixodes columnae (0.03 %). Of 2160 DNA samples extracted from the ticks, the gltA gene and the 17-kDa antigen gene of SFGR were detected in 67 samples. Among 1682 samples from adult and nymph ticks, the positive rate of SFGR was 2.7 %. Sequence analyses of the partial 17-kDa antigen gene demonstrated that the detected SFGR were classified into 8 groups (G1 to G8). The sequences of G2, G4, G5, G6, and G7 were either identical to or differed by one base pair from those of Rickettsia asiatica, Rickettsia tamurae, Rickettsia monacensis, Rickettsia canadensis, and Rickettsia felis, respectively. CONCLUSION: The present study revealed a diverse tick fauna in Ibaraki prefecture, including detection of species commonly found in southwestern Japan. Although the prevalence of SFGR in ticks was lower than in previous studies, several SFGR causing human infection may be present.

Japanese spotted fever complicated by acute sensorineural hearing loss.

Japanese spotted fever is an emerging rickettsiosis caused by Rickettsia japonica and is characterized by high fever, rash, and eschar formation. Other symptoms are often vague and nonspecific and include headaches, nausea, vomiting, and myalgia. We present a case of a 46-year-old woman with Japanese spotted fever, complicated by transient bilateral sensorineural hearing loss and presenting cutaneous IgM/IgG immune complex vasculitis. The patient was admitted with a history of several days of high fever, generalized skin erythema, and hearing impairment. Laboratory findings revealed thrombocytopenia and elevated liver enzyme and C-reactive protein levels. Pure-tone audiometry revealed bilateral sensorineural hearing loss, and a skin biopsy revealed leukocytoclastic vasculitis with deposition of C3 and IgM on the vessel walls. Under the tentative diagnosis of rickettsiosis, scrub typhus, or Japanese spotted fever, the patient was treated with minocycline, and her symptoms improved within approximately 10 days. A definitive diagnosis was made on the basis of a serological test showing increased antibody levels against Rickettsia japonica. Japanese spotted fever can cause transient sensorineural hearing loss, a rare complication that presents with cutaneous IgM/IgG immune complex vasculitis.

Changing trends in Japanese spotted fever epidemiology in Shimane, Japan: A two-decade retrospective study with emphasis on the COVID-19 pandemic era.

INTRODUCTION: The objective of this study is to evaluate the epidemiological characteristics of Japanese Spotted Fever (JSF) cases reported through the National Epidemiological Surveillance of Infectious Disease (NESID) system in Shimane Prefecture, Japan, from 2000 to 2022, encompassing the periods before and during the COVID-19 pandemic period. METHODS: A retrospective analysis was conducted on JSF cases reported to the NESID system in Shimane Prefecture between 2000 and 2022. Population data were obtained from the Statistical Information of Shimane. Poisson regression analysis was employed to examine the relationship between the annual prevalence rate of JSF and the COVID-19 pandemic. RESULTS: A total of 301 JSF cases were analyzed during the study period. Even the pre-COVID-19 pandemic period, a gradual and significant increase in the prevalence rate was observed (prevalence rate = 1.03, 95% CI: 1.01-1.05; p = 0.01), and a rapid increase was noted since 2020 (prevalence rate = 1.57, 95% CI: 1.39-1.78; p < 0.01). The slope during the pre-COVID-19 pandemic period was estimated to have significantly increased (p < 0.01). CONCLUSIONS: Our findings suggest that while the prevalence rate of JSF had exhibited a slight increase in the years preceding the COVID-19 pandemic, it demonstrated a more significant increase following the pandemic in Shimane Prefecture. JSF has increased since 2020 and may be linked to COVID-19 pandemic. The COVID-19 pandemic has had a substantial impact on global health, underscoring the importance of investigating the prevalence of specific infectious diseases and other health-related indicators to accurately assess the pandemic's impact.

Single particle cryo-EM analysis of Rickettsia conorii Sca2 reveals a formin-like core.

Spotted fever group Rickettsia undergo actin-based motility inside infected eukaryotic cells using Sca2 (surface cell antigen 2): an âˆ¼ 1800 amino-acid monomeric autotransporter protein that is surface-attached to the bacterium and responsible for the assembly of long unbranched actin tails. Sca2 is the only known functional mimic of eukaryotic formins, yet it shares no sequence similarities to the latter. Using structural and biochemical approaches we have previously shown that Sca2 uses a novel actin assembly mechanism. The first âˆ¼ 400 amino acids fold into helix-loop-helix repeats that form a crescent shape reminiscent of a formin FH2 monomer. Additionally, the N- and C- terminal halves of Sca2 display intramolecular interaction in an end-to-end manner and cooperate for actin assembly, mimicking a formin FH2 dimer. Towards a better structural understanding of this mechanism, we performed single-particle cryo-electron microscopy analysis of Sca2. While high-resolution structural details remain elusive, our model confirms the presence of a formin-like core: Sca2 indeed forms a doughnut shape, similar in diameter to a formin FH2 dimer and can accommodate two actin subunits. Extra electron density, thought to be contributed by the C-terminal repeat domain (CRD), covering one side is also observed. This structural analysis allows us to propose an updated model where nucleation proceeds by encircling two actin subunits, and elongation proceeds either by a formin-like mechanism that necessitates conformational changes in the observed Sca2 model, or via an insertional mechanism akin to that observed in the ParMRC system.

Spotted Fever and Typhus Group Rickettsiae in Dogs and Humans, Mexico, 2022.

We found serologic evidence of spotted fever group Rickettsia in humans and dogs and typhus group Rickettsia in dogs in Reynosa, Mexico. Our investigation revealed serologic samples reactive to spotted fever group Rickettsia in 5 community members, which highlights a potential rickettsial transmission scenario in this region.

Nonnegligible Seroprevalence and Predictors of Murine Typhus, Japan.

To elucidate the epidemiology of murine typhus, which is infrequently reported in Japan, we conducted a cross-sectional study involving 2,382 residents of rickettsiosis-endemic areas in Honshu Island during August-November 2020. Rickettsia typhi seroprevalence rate was higher than that of Orientia tsutsugamushi, indicating that murine typhus is a neglected disease.

Clinical Forms of Japanese Spotted Fever from Case-Series Study, Zigui County, Hubei Province, China, 2021.

We report a case-series study of 5 patients with Japanese spotted fever from the Three Gorges Area in China, including 1 fatal case. Seroprevalence of Rickettsia japonica was ≈21% among the local population. Our report highlights the emerging potential threat to human health of Japanese spotted fever in the area.

Spotted fever rickettsia-induced microvascular endothelial barrier dysfunction is delayed by the calcium channel blocker benidipine.

The tick-borne bacterium Rickettsia parkeri is an obligate intracellular pathogen that belongs to spotted fever group rickettsia (SFGR). The SFG pathogens are characterized by their ability to infect and rapidly proliferate inside host vascular endothelial cells that eventually result in impairment of vascular endothelium barrier functions. Benidipine, a wide range dihydropyridine calcium channel blocker, is used to prevent and treat cardiovascular diseases. In this study, we tested whether benidipine has protective effects against rickettsia-induced microvascular endothelial cell barrier dysfunction in vitro. We utilized an in vitro vascular model consisting of transformed human brain microvascular endothelial cells (tHBMECs) and continuously monitored transendothelial electric resistance (TEER) across the cell monolayer. We found that during the late stages of infection when we observed TEER decrease and when there was a gradual increase of the cytoplasmic [Ca2+], benidipine prevented these rickettsia-induced effects. In contrast, nifedipine, another cardiovascular dihydropyridine channel blocker specific for L-type Ca2+ channels, did not prevent R. parkeri-induced drop of TEER. Additionally, neither drug was bactericidal. These data suggest that growth of R. parkeri inside endothelial cells is associated with impairment of endothelial cell monolayer integrity due to Ca2+ flooding through specific, benidipine-sensitive T- or N/Q-type Ca2+ channels but not through nifedipine-sensitive L-type Ca2+ channels. Further study will be required to discern the exact nature of the Ca2+ channels and Ca2+ transporting system(s) involved, any contributions of the pathogen toward this process, as well as the suitability of benidipine and new dihydropyridine derivatives as complimentary therapeutic drugs against Rickettsia-induced vascular failure.

Epidemiological study of ticks harbouring Aeromonas hydrophila in areas endemic and non-endemic to Japanese-spotted fever.

OBJECTIVES: Aeromonas spp. often cause life-threatening diseases, including necrotizing fasciitis, which may lead to septic shock and ultimately death. Aeromonas infections are believed to be transmitted via minor wounds or the consumption of fresh fish. However, after the detection of Aeromonas hydrophila in ticks in areas endemic to Japanese-spotted fever (JSF), a novel transmission route of A. hydrophila (i.e., via tick bites) has been proposed. We investigated the prevalence of A. hydrophila in ticks in areas endemic and not endemic to JSF in the Mie Prefecture, Japan. METHODS: We collected ticks from endemic and nonendemic areas in summer and winter and assessed them for presence of A. hydrophila using polymerase chain reaction. RESULTS: Six A. hydrophila isolates were obtained from 95 ticks in endemic areas, whereas one A. hydrophila isolate was obtained from 142 ticks in non-endemic areas, in summer. All ticks that harboured A. hydrophila were Haemaphysalis longicornis (H.L); these ticks were almost at the larval stage and also carried Rickettsia spp. in the endemic area. In contrast, 51 and 41 ticks in the endemic and non-endemic areas were captured in winter, respectively; A. hydrophila was not detected in these. CONCLUSIONS: This study revealed the prevalence of tick-borne A. hydrophila. Therefore, the risk of transmission of A. hydrophila via a tick bite should be considered in the following conditions: areas abundant in H. L. harbouring Rickettsia spp., in areas endemic for JSF, presence of ticks in the larval stage and during the summer season.

Analysis of Rocky Mountain spotted fever cases in Northern Mexico reveals genetic variability of Rickettsia rickettsii and the different distribution of genotypes.

Rickettsioses have been reported in parts of Mexico since the last century, with Rocky Mountain spotted fever (RMSF) being one of the most prevalent in northern states. Unfortunately, fatality rates for RMSF in Mexico are higher than in other countries, like the USA. The reason for this difference in fatality rates is currently unknown and could be associated with a genotype of the bacterium, but no comparative molecular typing has been conducted in Mexico to date. The purpose of this study was to analyze 47 RMSF samples with different outcomes from several states in northern Mexico to know the genetic variability of Rickettsia rickettsii, as well as to reconstruct its phylogeny, for which the following intergenic regions were sequenced: RR0155-rpmB, cspA-ksgA, RR1240-tlc5, and Spo0J-abc T1, as well as the following partial genes: ompA, ompB, and gltA. We identified 8 genotypes with different distribution and prevalence among the states analyzed, as well as a different association with case outcome; these genotypes were clustered in 2 clades and 5 lineages were revealed, some of them probably exclusive from Mexico.

Phylogenic position and low genomic diversity of "Candidatus Rickettsia kotlanii" inferred by complete genome sequences of two Japanese isolates.

Many Rickettsia species of the spotted fever group (SFG) cause tick-borne diseases known as "spotted fever." One of the candidate SFG Rickettsia species is "Candidatus Rickettsia kotlanii," which was first detected in Haemaphysalis concinna in Hungary in 2006. However, its precise phylogenetic position in the SFG is not clear because only single-gene sequence-based phylogenetic analyses were performed using very limited genes. Here, we present the complete genome sequences of two Japanese "Ca. R. kotlanii" isolates, which differed only by a 135 bp insertion/deletion (InDel). Using these genomes and publicly available whole genome sequences of other Rickettsia species, the precise phylogenetic position of "Ca. R. kotlanii" in Rickettsia was determined to be in a clade of the SFG. The phylogenetic relationships and average nucleotide identity of "Ca. R. kotlanii" relative to the other species indicated that "Ca. R. kotlanii" is an independent taxon in the SFG. Notably, although the genomes of the two isolates were almost identical, the isolates were obtained from different tick species in different regions and years, suggesting extremely low genomic diversity in "Ca. R. kotlanii." While the genome of "Ca. R. kotlanii" is the smallest in the transitional group and SFG Rickettsia sequenced to date, we identified genes uniquely present or absent in "Ca. R. kotlanii," but most were apparently degraded. Therefore, analyses of differences at the sequence (single nucleotide polymorphisms and small InDels) or gene expression level will be required to understand the functional or physiological features unique to "Ca. R. kotlanii."

Confirmation of the presence of Rickettsia felis infecting Ornithodoros puertoricensis in Mexico.

Soft ticks are neglected competent vectors of a wide range of pathogenic microorganisms, among which bacteria of the genera Rickettsia and Borrelia stand out. In Mexico, previous studies have shown the presence of a member of the Ornithodoros talaje complex in the Virginia opossum (Didelphis virginiana Didelphimorphia: Didelphidae Kerr) from southeastern Mexico. However, its specific identification has not been achieved. Two D. virginiana were treated in a private clinic during the period of April-May 2022. Tick larvae were manually removed, DNA extraction was performed, and some genes from various bacterial and parasitic pathogens were amplified and sequenced. A total of 96 larvae were recovered, which were morphologically identified as Ornithodoros puertoricensis (Ixodida: Argasidae Fox); the 16 S sequences showed a similarity of 96.79%-99.51% with sequences of O. puertoricensis from Panama and Colombia. The presence of Rickettsia felis (Rickettsiales: Rickettsiaceae Bouyer et al.) was detected in 15 specimens from one host. The soft tick O. puertoricensis is recorded for the first time as an ectoparasite of the Virginia opossum in America and represents the second report for this soft tick in Mexico since 1963. This represents the most northern record of this tick species in its geographic distribution and brings a new soft tick-Rickettsia association.

Peculiarities of Q fever and human cases reported so far in the Czech Republic.

INTRODUCTION: Q fever is a zoonosis with a worldwide occurrence. Coxiella burnetii infection is most commonly transmitted by inhalation of air containing contaminated dust in cow, sheep and goat farming areas. The other modes of transmission are alimentary route (ingestion) and through sucking ticks. We set ourselves the goal of presenting a descriptive analysis of cases of Q fever in the Czech Republic (CZ) and former Czechoslovakia and draw attention to this often-overlooked issue. METHODS: Summary of available information about Q fever was processed, and a narrative search of published cases of Q fever in the CZ and former Czechoslovakia, in Czech, Slovak and English, without time restrictions was performed. Furthermore, a descriptive analysis of Q fever cases reported to the Czech infectious diseases reporting system in 1982-2021 was done. After analysis, the available information system data were supplemented with data from a search of published scientific literature and weekly reports on the current epidemiological situation of the public health protection authorities of the CZ. RESULTS: The disease has been reported in former Czechoslovakia and then in CZ since 1952. In 1952-1954, six outbreaks were reported with a total of 150 cases, mostly in connection with work with cattle. In 1980, a large-scale outbreak of Q fever affected 526 employees of the cotton production plant at Staré Mesto near Uherské Hradiste. Otherwise, units to dozens of cases were reported. From 1993 to 2021, 27 cases of the disease were detected in the CZ, of which 22 (81.5%) occurred in men. The age range was 0-60 years (mean 31, median 30 years). Seasonality by reporting month was highest in January and September. CONCLUSION: There has been a decline in human cases of Q fever in the European Union (EU) in recent years, and only few cases of the disease occur in the CZ. Still, due to potential severity of the disease, the current climate change with the consequent increase in the spread of ticks as vectors of Coxiella, and animal movements associated with the global market, it is important to consider Q fever in the differential diagnosis. As part of the prevention, it is necessary to ensure compliance with basic hygiene rules, especially in at-risk occupations, and to consume only pasteurized dairy products. Vaccination of humans is not available in EU countries, although vaccination of livestock is possible.

[Autochthonous Rickettsia parkeri rickettsiosis in the Paranaense Forest, Misiones, Argentina]. / Caso autóctono de rickettsiosis por Rickettsia parkeri en la Selva Paranaense, Misiones, Argentina.

We report an autochthonous case of Rickettsia parkeri rickettsiosis occurred in June 2018 in a forested area of the Urugua-í Provincial Park, Misiones, Argentina. No previous records of this disease in humans have been previously reported in this region. The epidemiological, ecological, clinical, and laboratory features required for a proper diagnosis and adequate treatment are described here. The fact of considering rickettsiosis as a differential diagnosis in a patient with exanthematic acute febrile syndrome is highlighted, being the epidemiological history of exposure to the vector (ticks of the genus Amblyomma) an essential element.