What's New in Rocky Mountain Spotted Fever?

Investigating and Summarizing Information Resources Related to the Clinical Presentation and Diagnosis of Cutaneous Manifestations of Infectious Diseases in Patients With Skin of Color

Patients with skin of color (SOC) present diseases differently in many circumstances, yet there is a lack of information regarding the presentation and diagnosis of cutaneous manifestations in such patients experiencing infectious diseases. Therefore, we conducted a scoping review to investigate and summarize information pertaining to the clinical presentation and diagnosis of cutaneous manifestations of infectious diseases in patients with SOC focusing on the following viral, bacterial, toxin-mediated, and infestation diseases and fungal infections: human immunodeficiency virus, shingles, impetigo, scarlet fever, Lyme disease, toxic shock syndrome, scabies, rickettsioses, and cutaneous fungal infections. This scoping review identified literature gaps regarding cutaneous manifestations of infectious diseases in patients with SOC such as a lack of visual examples and more precise descriptions of common infectious diseases. The lack of better-quality literature and educational resources describing cutaneous manifestations of infectious diseases in patients with SOC may contribute to care barriers; therefore, more research and collaboration are needed in the specialties of both infectious diseases and dermatology.

The anal pore route is efficient to infect Amblyomma spp. ticks with Rickettsia rickettsii and allows the assessment of the role played by infection control targets

Adult Amblyomma sculptum and Amblyomma aureolatum ticks are partially refractory to Rickettsia rickettsii when fed on infected hosts, hindering the functional characterization of potentially protective targets in the bacterial acquisition. In the current study, we used the anal pore route to infect adult A. sculptum and A. aureolatum ticks with R. rickettsii and to assess the effects of the knockdown of microplusin in infection control. The anal pore route was efficient to infect both species, resulting in a prevalence of around 100% of infected ticks. Higher loads of R. rickettsii were detected in microplusin-silenced A. aureolatum in relation to the control, as previously obtained when microplusin-silenced ticks were fed on R. rickettsii-infected rabbits. This is the first report showing R. rickettsii infection through the anal pore in Amblyomma ticks, highlighting this route as a powerful tool to assess the role played by additional targets in the control of pathogens.

Empirical Administration of Doxycycline for Rocky Mountain Spotted Fever: A Case Report

Rocky Mountain spotted fever (RMSF) is a tick-borne illness that can cause extreme sickness, even death, in otherwise healthy individuals. Sometimes, it is difficult to confirm the diagnosis as the rash often lags behind other symptoms of the illness and may not occur at all. Other symptoms of RMSF are nonspecific, such as fever, headache, and malaise. Besides the confirmatory serology test, antibody titers remain negative in the early phase of the illness. Here, we reported a case of a 21-year-old male who presented with fever, mild headache, body aches, joint pain, dry cough, and characteristic maculopapular rash after visiting a tick-prone area. Doxycycline was started because symptoms and laboratory values heightened our suspicion for the diagnosis of RMSF. His condition improved gradually, and his labs became normal. Our study supports the empirical use of doxycycline in suspected RMSF cases.

False-Positive Serology for Rocky Mountain Spotted Fever in Long Island, New York, during 2011-2021

Cases of rocky mountain spotted fever (RMSF) are increasingly reported every year in Long Island, New York. In clinical practice, an uncommonly high number of referrals with a positive RMSF IgG test result have been seen in our tick-borne disease clinic. The aim of this study is to describe the clinical-epidemiological characteristics and outcomes of hospitalized patients with positive serologies for RMSF in our academic center in Long Island, NY. We found that out of twenty-four patients with a positive serology for RMSF, only one case met the case definition per CDC criteria, two had suspected RMSF, and the other twenty-one did not have a clinical picture consistent with RMSF. A high number of false-positive RMSF serology may be due to other spotted fever rickettsioses in Long Island. Further studies are needed to investigate the presence of another Rickettsia spp. (such as Rickettsia amblyommatis) in this area that may affect humans.

Modeling of Control Efforts against Rhipicephalus sanguineus, the Vector of Rocky Mountain Spotted Fever in Sonora Mexico

Rocky Mountain spotted fever (RMSF) is a significant health problem in Sonora, Mexico. The tick vector, Rhipicephalus sanguineus, feeds almost exclusively on domestic dogs that, in this region, also serve as the reservoir for the tick-borne pathogen, Rickettsia rickettsii. A process-based mathematical model of the life cycle of R. sanguineus was developed to predict combinations of insecticidal dog collars and long-lasting insecticidal wall treatments resulting in suppression of indoor tick populations. Because of a high burden of RMSF in a rural community near the Sonora state capital of Hermosillo, a test area was treated with a combination of insecticidal dog collars and long-lasting insecticidal wall treatments from March 2018 to April 2019, with subsequent reduction in RMSF cases and deaths. An estimated 80% of the dogs in the area had collars applied and 15% of the houses were treated. Data on tick abundance on walls and dogs, collected during this intervention, were used to parameterize the model. Model results show a variety of treatment combinations likely to be as successful as the one carried out in the test community.

Induced Transient Immune Tolerance in Ticks and Vertebrate Host: A Keystone of Tick-Borne Diseases?

Ticks and tick transmitted infectious agents are increasing global public health threats due to increasing abundance, expanding geographic ranges of vectors and pathogens, and emerging tick-borne infectious agents. Greater understanding of tick, host, and pathogen interactions will contribute to development of novel tick control and disease prevention strategies. Tick-borne pathogens adapt in multiple ways to very different tick and vertebrate host environments and defenses. Ticks effectively pharmacomodulate by its saliva host innate and adaptive immune defenses. In this review, we examine the idea that successful synergy between tick and tick-borne pathogen results in host immune tolerance that facilitates successful tick infection and feeding, creates a favorable site for pathogen introduction, modulates cutaneous and systemic immune defenses to establish infection, and contributes to successful long-term infection. Tick, host, and pathogen elements examined here include interaction of tick innate immunity and microbiome with tick-borne pathogens; tick modulation of host cutaneous defenses prior to pathogen transmission; how tick and pathogen target vertebrate host defenses that lead to different modes of interaction and host infection status (reservoir, incompetent, resistant, clinically ill); tick saliva bioactive molecules as important factors in determining those pathogens for which the tick is a competent vector; and, the need for translational studies to advance this field of study. Gaps in our understanding of these relationships are identified, that if successfully addressed, can advance the development of strategies to successfully disrupt both tick feeding and pathogen transmission.

Epidemiology and Clinical Features of Rocky Mountain Spotted Fever from Enhanced Surveillance, Sonora, Mexico: 2015-2018

Rocky Mountain spotted fever (RMSF), caused by Rickettsia rickettsii, is a severe and potentially fatal tick-borne disease. In 2015, Mexico issued a declaration of epidemiologic emergency in response to ongoing outbreaks of RMSF in northern Mexico. Sonora state is one of the most heavily impacted states in Mexico, with historic case fatality rates (CFRs) of 18%. We summarized data from enhanced surveillance to understand demographic, clinical, and treatment factors associated with the high mortality. We conducted a retrospective review of confirmed and probable RMSF cases reported to the General Directorate of Health Promotion and Disease Prevention in Sonora. A case of RMSF is defined as fever (> 38.5°C), plus two symptoms, and epidemiologic criteria. A confirmed case requires laboratory evidence. During 2015-2018, a total of 510 cases of RMSF were reported; 252 (49%) were in persons aged ≤ 18 years. Case fatality rate was 44% (n = 222). Older age and being confirmed by PCR were associated with fatal outcome (P-value < 0.01). The mean time from onset of symptoms to treatment with doxycycline was 7.9 days (SD ± 5.5). Hot spot analysis revealed neither areas of inordinately high nor low incidence, rather clusters of disease in population centers. The CFR for RMSF in Sonora remains high, and a large proportion of cases are seen in persons aged ≤ 18 years. Whereas previously children experienced a disproportionately high CFR, interventions have reversed this trend. Disease clusters in urban nuclei, but location remains a predictor of fatal outcome.

Detecção de anticorpos anti-Rickettsia rickettsii em cães residentes em área negligenciada no município de São Paulo, SP, Brasil

RESUMO A febre maculosa brasileira (FMB), descrita inicialmente nos Estados Unidos como febre maculosa das Montanhas Rochosas, é uma antropozoonose relatada apenas no continente americano e causada pela bactéria Rickettsia rickettsii. No Brasil a transmissão ocorre sobretudo pela picada de carrapatos do gênero Amblyomma spp. A doença foi inicialmente descrita como de transmissão em áreas rurais e silvestres, no entanto áreas periurbanas e urbanas vêm apresentando casos, principalmente relacionados com a presença de humanos residindo em pequenos fragmentos de mata ciliar. O presente estudo teve por objetivo elucidar a dispersão da FMB nas proximidades dos reservatórios Guarapiranga e Billings, na cidade de São Paulo, SP. Para tanto, a presença de anticorpos anti-R. rickettsii, Rickettsia parkeri e Rickettsia bellii foi avaliada em cães atendidos nas campanhas de esterilização cirúrgica e residentes ao redor dos reservatórios. Foram coletadas amostras de 393 cães, e as amostras de soro foram analisadas pela reação de imunofluorescência indireta (RIFI), com ponto de corte de 1:64. Os títulos para R. rickettsii variaram de 256 a 4096, com positividade de 3,3% (13/393); para R. bellii, de 128 a 1024 e 4,1% (16/393) de positivos, e um único animal (0,25%) foi soropositivo para R. parkeri, com título de 128. Os achados permitem concluir que a região de estudo apresenta condições de se tornar uma possível área com casos de FMB, pois comporta fragmentação de Mata Atlântica, condições essas ideais para a manutenção do vetor do gênero Amblyomma já descrito na região, bem como para a presença da Rickettsia rickettsii circulante entre os cães, confirmada pela existência de anticorpos. Condutas referentes à conscientização da população por meio de trabalhos educacionais devem ser implantadas para a prevenção da doença na população da área.

The intracellular bacterium Rickettsia rickettsii exerts an inhibitory effect on the apoptosis of tick cells

BACKGROUND

Rickettsia rickettsii is a tick-borne obligate intracellular bacterium that causes Rocky Mountain spotted fever, a life-threatening illness. To obtain an insight into the vector-pathogen interactions, we assessed the effects of infection with R. rickettsii on the proteome cells of the tick embryonic cell line BME26.

METHODS

The proteome of BME26 cells was determined by label-free high-performance liquid chromatography coupled with tandem mass spectrometry analysis. Also evaluated were the effects of infection on the activity of caspase-3, assessed by the hydrolysis of a synthetic fluorogenic substrate in enzymatic assays, and on the exposition of phosphatidyserine, evaluated by live-cell fluorescence microscopy after labeling with annexin-V. Finally, the effects of activation or inhibition of caspase-3 activity on the growth of R. rickettsii in BME26 cells was determined.

RESULTS

Tick proteins of different functional classes were modulated in a time-dependent manner by R. rickettsii infection. Regarding proteins involved in apoptosis, certain negative regulators were downregulated at the initial phase of the infection (6 h) but upregulated in the middle of the exponential phase of the bacterial growth (48 h). Microorganisms are known to be able to inhibit apoptosis of the host cell to ensure their survival and proliferation. We therefore evaluated the effects of infection on classic features of apoptotic cells and observed DNA fragmentation exclusively in noninfected cells. Moreover, both caspase-3 activity and phosphatidylserine exposition were lower in infected than in noninfected cells. Importantly, while the activation of caspase-3 exerted a detrimental effect on rickettsial proliferation, its inhibition increased bacterial growth.

CONCLUSIONS

Taken together, these results show that R. rickettsii modulates the proteome and exerts an inhibitory effect on apoptosis in tick cellsthat seems to be important to ensure cell colonization.

Knowledge, Attitudes, and Practices Related to Rocky Mountain Spotted Fever in Hermosillo, México

Rocky Mountain spotted fever (RMSF) is a serious disease in northwest Mexico, particularly in low-income communities. This study aimed to evaluate RMSF-related knowledge, attitudes, and practices in an endemic urban area with a high burden of the disease. A cross-sectional study design using a non-probabilistic household survey was conducted with 400 residents in Hermosillo, Mexico. Primary themes assessed included dog and tick-related exposure, RMSF knowledge, healthcare-seeking behavior, sociodemographic data, and household information. The majority (59%) of those surveyed had heard about RMSF, although only 36% of RMSF-aware respondents knew any RMSF symptoms. Among RMSF-aware respondents, 26% did not know or were unsure of prevention strategies. Individuals in the low socioeconomic status (SES) stratum were less likely to have heard about RMSF (odds ratio [OR]: 0.39; 95% CI: 0.25-0.59), use dog collars or any other product to avoid ticks (OR: 0.40; 95% CI: 0.17-0.99), or check their dogs for ticks (OR: 0.25; 95% CI: 0.09-0.74). The likelihood of observing high numbers of free-roaming dogs in their neighborhood was four times higher in the low SES stratum (OR: 4.19; 95% CI: 2.10-8.38) than in the high SES stratum. These findings emphasize the need for an integrative community approach to improve early recognition of symptoms and knowledge of prevention strategies, particularly in low SES neighborhoods.

The Characteristics and Clinical Course of Patients with Scrub Typhus and Queensland Tick Typhus Infection Requiring Intensive Care Unit Admission: A 23-year Case Series from Queensland, Tropical Australia

Scrub typhus and Queensland tick typhus (QTT)-rickettsial infections endemic to tropical Australia-can cause life-threatening disease. This retrospective study examined the clinical course of all patients with laboratory-confirmed scrub typhus or QTT admitted to the intensive care unit (ICU) of a tertiary referral hospital in tropical Australia between 1997 and 2019. Of the 22 patients, 13 had scrub typhus and nine had QTT. The patients' median (interquartile range [IQR]) age was 50 (38-67) years; 14/22 (64%) had no comorbidity. Patients presented a median (IQR) of seven (5-10) days after symptom onset. Median (IQR) Acute Physiology and Chronic Health Evaluation II scores were 13 (9-17) for scrub typhus and 13 (10-15) for QTT cases (P = 0.61). Following hospital admission, the median (IQR) time to ICU admission was five (2-19) hours. The median (IQR, range) length of ICU stay was 4.4 (2.9-15.9, 0.8-33.8) days. Multi-organ support was required in 11/22 (50%), 5/22 (22%) required only vasopressor support, 2/22 (9%) required only invasive ventilation, and 4/22 (18%) were admitted for monitoring. Patients were ventilated using protective lung strategies, and fluid management was conservative. Standard vasopressors were used, indications for renal replacement therapy were conventional, and blood product usage was restrictive; 9/22 (41%) received corticosteroids. One patient with QTT died, and two (8%) additional patients with QTT developed purpura fulminans requiring digital amputation. Death or permanent disability occurred in 3/9 (33%) QTT and 0/13 scrub typhus cases (P = 0.055). Queensland tick typhus and scrub typhus can cause multi-organ failure requiring ICU care in otherwise well individuals. Queensland tick typhus appears to have a more severe clinical phenotype than previously believed.

Comparative analysis of the midgut microbiota of two natural tick vectors of Rickettsia rickettsii

Although the ticks Amblyomma sculptum and Amblyomma aureolatum are important vectors of Rickettsia rickettsii, causative agent of the life-threatening Rocky Mountain spotted fever, A. aureolatum is considerably more susceptible to infection than A. sculptum. As the microbiota can interfere with the colonization of arthropod midgut (MG) by pathogens, in the current study we analyzed the MG microbiota of both tick species. Our results revealed that the MG of A. aureolatum harbors a prominent microbiota, while A. sculptum does not. Remarkably, a significant reduction of the bacterial load was recorded in R. rickettsii-infected A. aureolatum. In addition, the taxonomy analysis of the MG bacterial community of A. aureolatum revealed a dominance of the genus Francisella, suggesting an endosymbiosis. This study is the first step in getting insights into the mechanisms underlying the interactions among Amblyomma species, their microbiota and R. rickettsii. Additional studies to better understand these mechanisms are required and may help the development of novel alternatives to block rickettsial transmission.

Molecular Detection of Spotted Fever Group Rickettsiae (Rickettsiales: Rickettsiaceae) in Dermacentor variabilis (Acari: Ixodidae) Collected Along the Platte River in South Central Nebraska

Dermacentor variabilis is the predominant tick species in Nebraska and is presumed to be the primary vector of Rickettsia rickettsii associated with cases of Rocky Mountain spotted fever (RMSF). Interestingly, RMSF cases in Nebraska have increased on a year-to-year basis, yet the prevalence of R. rickettsii in D. variabilis ticks has not been established for Nebraska. Here we sought to set a baseline for the prevalence of R. rickettsii and other spotted fever group (SFG) rickettsiae harbored by D. variabilis ticks. Over a 3-yr period, D. variabilis were collected along the Platte River in south central Nebraska. Individual tick DNA was analyzed using endpoint PCR to identify ticks carrying SFG rickettsiae. In total, 927 D. variabilis were analyzed by PCR and 38 (4.1%) ticks tested positive for SFG rickettsiae. Presumptive positives were sequenced to identify the Rickettsia species, of which 29 (76%) were R. montanensis, 5 (13%) were R. amblyommatis, 4 (11%) were R. bellii, and R. rickettsii was not detected. These data indicate that R. rickettsii is likely at a low prevalence in south central Nebraska and spillover of R. amblyommatis into D. variabilis is likely occurring due to the invasive lone star tick (Amblyomma americanum). In addition, our data suggest that R. montanensis and R. amblyommatis could be associated with the increase in SFG rickettsiae infections in Nebraska. This information will be of value to clinicians and the general public for evaluating diagnosis of disease- and risk-associated environmental exposure, respectively.

The Transcriptome of the Salivary Glands of Amblyomma aureolatum Reveals the Antimicrobial Peptide Microplusin as an Important Factor for the Tick Protection Against Rickettsia rickettsii Infection

The salivary glands (SG) of ixodid ticks play a pivotal role in blood feeding, producing both the cement and the saliva. The cement is an adhesive substance that helps the attachment of the tick to the host skin, while the saliva contains a rich mixture of antihemostatic, anti-inflammatory, and immunomodulatory substances that allow ticks to properly acquire the blood meal. The tick saliva is also a vehicle used by several pathogens to be transmitted to the vertebrate host, including various bacterial species from the genus Rickettsia. Rickettsia rickettsii is a tick-borne obligate intracellular bacterium that causes the severe Rocky Mountain spotted fever. In Brazil, the dog yellow tick Amblyomma aureolatum is a vector of R. rickettsii. In the current study, the effects of an experimental infection with R. rickettsii on the global gene expression profile of A. aureolatum SG was determined by next-generation RNA sequencing. A total of 260 coding sequences (CDSs) were modulated by infection, among which 161 were upregulated and 99 were downregulated. Regarding CDSs in the immunity category, we highlight one sequence encoding one microplusin-like antimicrobial peptide (AMP) (Ambaur-69859). AMPs are important effectors of the arthropod immune system, which lack the adaptive response of the immune system of vertebrates. The expression of microplusin was confirmed to be significantly upregulated in the SG as well as in the midgut (MG) of infected A. aureolatum by a quantitative polymerase chain reaction preceded by reverse transcription. The knockdown of the microplusin expression by RNA interference caused a significant increase in the prevalence of infected ticks in relation to the control. In addition, a higher rickettsial load of one order of magnitude was recorded in both the MG and SG of ticks that received microplusin-specific dsRNA. No effect of microplusin knockdown was observed on the R. rickettsii transmission to rabbits. Moreover, no significant differences in tick engorgement and oviposition were recorded in ticks that received dsMicroplusin, demonstrating that microplusin knockdown has no effect on tick fitness. Further studies must be performed to determine the mechanism of action of this AMP against R. rickettsii.

[A fatal case series of Rocky Mountain spotted fever in Sonora, México]

INTRODUCTION

Rocky Mountain spotted fever is a highly lethal infectious disease, particularly if specific treatment with doxycycline is given belatedly.

OBJECTIVE

To describe the clinical profile of fatal Rocky Mountain spotted fever cases in hospitalized patients in the state of Sonora, México.

MATERIALS AND METHODS

We conducted a cross-sectional study on a series of 47 deaths caused by Rickettsia rickettsii from 2013 to 2016. The diagnosis of Rocky Mountain spotted fever was confirmed in a single blood sample by polymerase chain reaction (PCR) or by a four-fold increase in immunoglobulin G measured in paired samples analyzed by indirect immunofluorescence. Clinical and laboratory characteristics were compared stratifying subjects into two groups: pediatric and adult.

RESULTS

There were no differences in clinical characteristics between groups; petechial rash was the most frequent sign (96%), followed by headache (70%) and myalgia (67%). Although that doxycycline was administered before the fifth day from the onset of symptoms, death occurred in 55% of patients. In clinical laboratory, thrombocytopenia, and biomarkers of liver acute failure and acute kidney failure were the most frequent.

CONCLUSION

Rocky Mountain spotted fever remains as one of the most lethal infectious diseases, which may be related not only to the lack of diagnostic suspicion and delayed administration of doxycycline, but to genotypic characteristics of Rickettsia rickettsii that may play a role in the variability of the fatality rate that has been reported in other geographical regions where the disease is endemic.

Medical knowledge related to Rocky Mountain spotted fever in Sonora, Mexico

Background

Rocky Mountain spotted fever (RMSF) is a tick-borne disease with a high case-fatality rate unless diagnosed promptly and treated timely with doxycycline. Physician knowledge about presentation and treatment can improve outcomes of RMSF in endemic regions, such as Sonora in northern Mexico, where RMSF has caused 1348 non-fatal cases and 247 deaths from 2003 to 2016.

Methods

A cross-sectional study was conducted with 343 physicians working in medical facilities in Sonora, Mexico. A 25-item questionnaire explored physician knowledge of clinical, epidemiological and preventive aspects of RMSF.

Results

Only 62% of physicians agreed that doxycycline should be used as the first choice treatment for children under 8 years with suspected RMSF. Additionally, 40% of primary care physicians correctly identified the time to initiate doxycycline, and 32% correctly identified the case-fatality rate of untreated RMSF in all patients.

Conclusions

Inadequate medical knowledge may adversely affect how patients infected with Rickettsia rickettsii are diagnosed and treated. Educational programs that improve the risk perception and medical knowledge about RMSF should be targeted at physicians most likely to have initial contact with diseased patients.

Suspected and Confirmed Vector-Borne Rickettsioses of North America Associated with Human Diseases

The identification of pathogenic rickettsial agents has expanded over the last two decades. In North America, the majority of human cases are caused by tick-borne rickettsioses but rickettsiae transmitted by lice, fleas, mites and other arthropods are also responsible for clinical disease. Symptoms are generally nonspecific or mimic other infectious diseases; therefore, diagnosis and treatment may be delayed. While infection with most rickettsioses is relatively mild, delayed diagnosis and treatment may lead to increased morbidity and mortality. This review will discuss the ecology, epidemiology and public health importance of suspected and confirmed vector-transmitted Rickettsia species of North America associated with human diseases.

Retrospective Study of Rocky Mountain Spotted Fever in Children

BACKGROUND/OBJECTIVES

Rocky Mountain spotted fever (RMSF), a lethal tick-borne illness, is prevalent in the south central United States. Children younger than 10 years old have the greatest risk of fatal outcome from RMSF. The objective of the current study was to review pediatric cases of RMSF seen in the dermatology consult service and to evaluate dermatology's role in the diagnosis and management of this disease.

METHODS

A retrospective review was performed of inpatient dermatology consultations at a tertiary care center in North Carolina from 2001 to 2011. Data collected included patient demographic characteristics, symptoms, pre- and postconsultation diagnoses, diagnostic procedures, length of hospital stay, and outcome.

RESULTS

A total of 3,912 consultations were conducted in the dermatology service over 10 years. Six patients with RMSF, ranging in age from 22 months to 10 years (mean 5.1 years), were evaluated during April, May, and June. All preconsultation diagnoses included RMSF in the differential diagnosis. All patients underwent skin biopsies, and a culture was obtained in one case. Fifty percent of patients died within 4 days of hospitalization.

CONCLUSIONS

Variables associated with mortality from RMSF are delayed diagnosis and initiation of antirickettsial therapy. Physicians should consider RMSF in children presenting with fever and rash during the summer months. Dermatology consultation is useful in evaluating patients with suspicious clinical features of RMSF with skin findings.

Predictive Factors for Fatal Tick-Borne Spotted Fever in Brazil

In Brazil, two pathogenic Rickettsia species have been identified causing tick-borne spotted fever (SF). The aetiological agent Rickettsia rickettsii causes serious illness, particularly in the south-eastern region of the country. Moreover, the Rickettsia sp. strain Atlantic Rainforest cause milder clinical manifestations in south-eastern, south and north-east regions. This study has sought to analyse predictive factors for fatal SF. A case-control study was performed using disease notification records in Brazil. The cases included were individuals with laboratory confirmation and fatal progression of SF, while the controls included individuals with SF who were cured. A total of 386 cases and 415 controls were identified (1 : 1.1), and the cases and controls were similar in age. The factors identified as being protective against death were reported presence of ticks (odds ratio [OR], 0.60; 95% confidence interval [CI], 0.41-0.88), residing in urban areas (OR, 0.47, 95% CI, 0.31-0.74) and presenting lymphadenopathy (OR, 0.43; 95% CI, 0.23-0.82). Males exhibited a greater chance of death (OR, 1.57; 95% CI, 1.13-2.18), as did patients who were hospitalized (OR, 10.82; 95% CI, 6.38-18.35) and who presented hypotension or shock (OR, 10.80; 95% CI, 7.33-15.93), seizures (OR, 11.24; 95% CI, 6.49-19.45) and coma (OR of 15.16; 95% CI, 8.51-27.02). The study demonstrates the severity profile of the SF cases, defined either as the frequency of hospitalization (even in cases that were cured) or as the increased frequency of the clinical complications typically found in critical patients. Opportune clinical diagnosis, a careful evaluation of the epidemiological aspects of the disease and adequate care for patients are determining factors for reducing SF fatality rates.

Intravenous Immunoglobulin Therapy for Cerebral Vasculitis Associated with Rocky Mountain Spotted Fever

Rocky Mountain spotted fever is a tick-borne illness that is prevalent in the south and the central United States, primarily during the summer months. Patients with delayed diagnosis can experience increased mortality and morbidity, particularly poor neurological outcome. We present a case of a 7-year-old girl with Rocky Mountain spotted fever who was admitted with severe neurological changes and septic shock on day 8 of illness. She was initially diagnosed with Kawasaki disease and treated with intravenous immunoglobulin. Her treatment also included doxycycline, vancomycin, and ceftriaxone due to concerns regarding Rocky Mountain spotted fever and bacterial sepsis. During hospitalization, the patient required mechanical ventilation for respiratory distress, inotropic support, and fluid resuscitation for hypotension. Titers for Rocky Mountain spotted fever were ultimately positive, with magnetic resonance imaging of the brain demonstrating numerous punctate foci of restricted diffusion within the supratentorium, including the corpus callosum and basal ganglia. Although the patient presented late in the disease course, she ultimately had a good neurological outcome. We theorized that administration of intravenous immunoglobulin prevented ongoing neurological injuries from the cerebral vasculitis, which are associated with Rocky Mountain spotted fever.

Comparative value of blood and skin samples for diagnosis of spotted fever group rickettsial infection in model animals

The definitive diagnosis of spotted fever group (SFG) rickettsioses in humans is challenging due to the retrospective nature and cross reactivity of the serological methods and the absence of reliable and consistent samples for molecular diagnostics. Existing data indicate the transient character of bacteremia in experimentally infected animals. The ability of arthropod vectors to acquire rickettsial infection from the laboratory animals in the absence of systemic infection and known tropism of rickettsial agents to endothelial cells of peripheral blood vessels underline the importance of local infection and consequently the diagnostic potential of skin samples. In order to evaluate the diagnostic sensitivity of rickettsial DNA detection in blood and skin samples, we compared results of PCR testing in parallel samples collected from model laboratory animals infected with Rickettsia rickettsii, Rickettsia parkeri and Rickettsia slovaca-like agent at different time points after infection. Skin samples were collected from ears - away from the site of tick placement and without eschars. Overall, testing of skin samples resulted in a higher proportion of positive results than testing of blood samples. Presented data from model animals demonstrates that testing of skin samples from sites of rickettsial proliferation can provide definitive molecular diagnosis of up to 60-70% of tick-borne SFG rickettsial infections during the acute stage of illness. Detection of pathogen DNA in cutaneous samples is a valuable alternative to blood-PCR at least in model animals.

Hierarchical Bayesian Spatio-Temporal Analysis of Climatic and Socio-Economic Determinants of Rocky Mountain Spotted Fever

This study aims to examine the spatio-temporal dynamics of Rocky Mountain spotted fever (RMSF) prevalence in four contiguous states of Midwestern United States, and to determine the impact of environmental and socio-economic factors associated with this disease. Bayesian hierarchical models were used to quantify space and time only trends and spatio-temporal interaction effect in the case reports submitted to the state health departments in the region. Various socio-economic, environmental and climatic covariates screened a priori in a bivariate procedure were added to a main-effects Bayesian model in progressive steps to evaluate important drivers of RMSF space-time patterns in the region. Our results show a steady increase in RMSF incidence over the study period to newer geographic areas, and the posterior probabilities of county-specific trends indicate clustering of high risk counties in the central and southern parts of the study region. At the spatial scale of a county, the prevalence levels of RMSF is influenced by poverty status, average relative humidity, and average land surface temperature (>35°C) in the region, and the relevance of these factors in the context of climate-change impacts on tick-borne diseases are discussed.

Ongoing Cerebral Vasculitis During Treatment of Rocky Mountain Spotted Fever

BACKGROUND

Rocky Mountain spotted fever is a tickborne infection that produces a systemic small-vessel vasculitis; its prognosis is excellent if appropriate treatment is initiated early. Because the advent of effective antirickettsial therapies predates the widespread use of brain magnetic resonance imaging, there are limited data on the effect of untreated Rocky Mountain spotted fever infection on neuroimaging studies.

PATIENT DESCRIPTION

We describe a 7-year-old girl with delayed treatment of Rocky Mountain spotted fever who suffered severe neurological impairment. Serial brain magnetic resonance images revealed a progressive "starry sky appearance," which is proposed to result from the same small vessel vasculitis that causes the characteristic skin rash of this infection.

CONCLUSION

Neurological injury can continue to occur despite specific antirickettsial therapy in Rocky Mountain spotted fever. This child's clinical features raise questions about the optimal management of this infection, particularly the utility of immune modulating therapies in cases of delayed treatment and neurological involvement.

Targeted knockout of the Rickettsia rickettsii OmpA surface antigen does not diminish virulence in a mammalian model system

Strains of Rickettsia rickettsii, the causative agent of Rocky Mountain spotted fever (RMSF), differ dramatically in virulence despite >99% genetic homology. Spotted fever group (SFG) rickettsiae produce two immunodominant outer membrane proteins, rickettsial OmpA (rOmpA) and rOmpB, which are conserved throughout the SFG and thought to be fundamental to pathogenesis. rOmpA is present in all virulent strains of R. rickettsii but is not produced in the only documented avirulent strain, Iowa, due to a premature stop codon. Here we report the creation of an isogenic ompA mutant in the highly virulent strain Sheila Smith by insertion of intronic RNA to create a premature stop codon 312 bp downstream of the 6,747-bp open reading frame initiation site (int312). Targeted insertion was accomplished using an LtrA group II intron retrohoming system. Growth and entry rates of Sheila Smith ompA::int312 in Vero cells remained comparable to those of the wild type. Virulence was assessed in a guinea pig model by challenge with 100 PFU of either ompA::int312 Sheila Smith or the wild type, but no significant difference in either fever peak (40.5°C) or duration (8 days) were shown between the wild type and the knockout. The ability to disrupt genes in a site-specific manner using an LtrA group II intron system provides an important new tool for evaluation of potential virulence determinants in rickettsial disease research.

R. rickettsii rOmpA is an immunodominant outer membrane autotransporter conserved in the spotted fever group. Previous studies and genomic comparisons suggest that rOmpA is involved in adhesion and may be critical for virulence. Little information is available for rickettsial virulence factors in an isogenic background, as limited systems for targeted gene disruption are currently available. Here we describe the creation of an rOmpA knockout by insertion of a premature stop codon into the 5′ end of the open reading frame using a group II intron system. An isogenic rOmpA knockout mutation in the highly virulent Sheila Smith strain did not cause attenuation in a guinea pig model of infection, and no altered phenotype was observed in cell culture. We conclude that rOmpA is not critical for virulence in a guinea pig model but may play a role in survival or transmission from the tick vector.

Diseases from North America: focus on tick-borne infections

Tick-borne infections are seen throughout the United States, with varying geographical locations. Many of these infections are also increasingly seen in Europe. Certain ticks (eg Ixodes) can transmit more than one infection. Diagnosis, particularly in early infection, can be challenging and therefore knowledge of the distinguishing clinical features and epidemiology of these diseases is important. Testing for Lyme disease often causes confusion for patients and medical providers, as serological tests may be negative in early infection and conversely may be positive for years after infection. Newer tests, such as the C6 ELISA, may play a role in Lyme diagnosis. Additionally, the value of a simple blood film should not be underestimated for diagnosing babesiosis and anaplasmosis. In certain situations, empiric therapy may be required for tick-borne infections as severe illness with multiorgan failure can occur, particularly in older and immunocompromised hosts. This review describes the more commonly seen tick-borne infections: Lyme, babesiosis, anaplasmosis and Rocky Mountain Spotted Fever. More recently identified tick-borne infections, such as southern tick-associated rash illness and Borrelia miyamotoi, are also covered.

Detection of Rickettsia rickettsii, Rickettsia parkeri, and Rickettsia akari in skin biopsy specimens using a multiplex real-time polymerase chain reaction assay

BACKGROUND

Rickettsia rickettsii, Rickettsia parkeri, and Rickettsia akari are the most common causes of spotted fever group rickettsioses indigenous to the United States. Infected patients characteristically present with a maculopapular rash, often accompanied by an inoculation eschar. Skin biopsy specimens are often obtained from these lesions for diagnostic evaluation. However, a species-specific diagnosis is achieved infrequently from pathologic specimens because immunohistochemical stains do not differentiate among the causative agents of spotted fever group rickettsiae, and existing polymerase chain reaction (PCR) assays generally target large gene segments that may be difficult or impossible to obtain from formalin-fixed tissues.

METHODS

This work describes the development and evaluation of a multiplex real-time PCR assay for the detection of these 3 Rickettsia species from formalin-fixed, paraffin-embedded (FFPE) skin biopsy specimens.

RESULTS

The multiplex PCR assay was specific at discriminating each species from FFPE controls of unrelated bacterial, viral, protozoan, and fungal pathogens that cause skin lesions, as well as other closely related spotted fever group Rickettsia species.

CONCLUSIONS

This multiplex real-time PCR demonstrates greater sensitivity than nested PCR assays in FFPE tissues and provides an effective method to specifically identify cases of Rocky Mountain spotted fever, rickettsialpox, and R. parkeri rickettsiosis by using skin biopsy specimens.

Atypical Rocky Mountain spotted fever with polyarticular arthritis

BACKGROUND

Rocky Mountain spotted fever (RMSF) is an acute, serious tick borne illness caused by Rickettsia rickettsi. Frequently, RMSF is manifested by headache, a typical rash and fever but atypical disease is common, making diagnosis difficult. Inflammatory arthritis as a manifestation is rare. The purpose of this study is to describe a patient with serologically proven RMSF who presented in an atypical manner with inflammatory arthritis of the small joints of the hands and to review the previously reported patients with rickettsial infection and inflammatory arthritis.

METHODS

An 18-year-old woman presented with a rash that began on the distal extremities and spread centrally, along with hand pain and swelling. She had tenderness and swelling of the metacarpophlangeal joints on examination in addition to an erythematosus macular rash and occasional fever.

RESULTS

Acute and convalescent serology demonstrated R rickettsi infection. She was successfully treated with doxycycline.

CONCLUSIONS

Inflammatory arthritis is a rare manifestation of RMSF or other rickettsial infection with 8 previously reported patients, only 1 of whom had RMSF. Physician must have a high index of suspicion for RMSF because of atypical presentations.

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

Tick-borne rickettsioses are caused by obligate intracellular bacteria belonging to the spotted fever group of the genus Rickettsia. These zoonoses are among the oldest known vector-borne diseases. However, in the past 25 years, the scope and importance of the recognized tick-associated rickettsial pathogens have increased dramatically, making this complex of diseases an ideal paradigm for the understanding of emerging and reemerging infections. Several species of tick-borne rickettsiae that were considered nonpathogenic for decades are now associated with human infections, and novel Rickettsia species of undetermined pathogenicity continue to be detected in or isolated from ticks around the world. This remarkable expansion of information has been driven largely by the use of molecular techniques that have facilitated the identification of novel and previously recognized rickettsiae in ticks. New approaches, such as swabbing of eschars to obtain material to be tested by PCR, have emerged in recent years and have played a role in describing emerging tick-borne rickettsioses. Here, we present the current knowledge on tick-borne rickettsiae and rickettsioses using a geographic approach toward the epidemiology of these diseases.

Non-lyme tick-borne diseases: a neurological perspective

Tick-borne diseases are prevalent throughout the world and present a diagnostic challenge owing to their nonspecific clinical symptoms. Many tick-borne diseases involve the central and peripheral nervous systems. Early diagnosis or at least suspicion of a tick-borne cause is necessary to institute early empiric treatment. After a brief review of tick biology, we present the most common tick-borne diseases. A brief discussion of epidemiology, the transmission route, and pathogenesis is followed by a discussion of the clinical manifestations, diagnosis and treatment options when available. The review emphasizes the infectious causes with a significant neurological manifestation.

Central Nervous System Infections

Central nervous system (CNS) infections—i.e., infections involving the brain (cerebrum and cerebellum), spinal cord, optic nerves, and their covering membranes—are medical emergencies that are associated with substantial morbidity, mortality, or long-term sequelae that may have catastrophic implications for the quality of life of affected individuals. Acute CNS infections that warrant neurointensive care (ICU) admission fall broadly into three categories—meningitis, encephalitis, and abscesses—and generally result from blood-borne spread of the respective microorganisms. Other causes of CNS infections include head trauma resulting in fractures at the base of the skull or the cribriform plate that can lead to an opening between the CNS and the sinuses, mastoid, the middle ear, or the nasopharynx. Extrinsic contamination of the CNS can occur intraoperatively during neurosurgical procedures. Also, implanted medical devices or adjunct hardware (e.g., shunts, ventriculostomies, or external drainage tubes) and congenital malformations (e.g., spina bifida or sinus tracts) can become colonized and serve as sources or foci of infection. Viruses, such as rabies, herpes simplex virus, or polioviruses, can spread to the CNS via intraneural pathways resulting in encephalitis. If infection occurs at sites (e.g., middle ear or mastoid) contiguous with the CNS, infection may spread directly into the CNS causing brain abscesses; alternatively, the organism may reach the CNS indirectly via venous drainage or the sheaths of cranial and spinal nerves. Abscesses also may become localized in the subdural or epidural spaces. Meningitis results if bacteria spread directly from an abscess to the subarachnoid space. CNS abscesses may be a result of pyogenic meningitis or from septic emboli associated with endocarditis, lung abscess, or other serious purulent infections. Breaches of the blood–brain barrier (BBB) can result in CNS infections. Causes of such breaches include damage (e.g., microhemorrhage or necrosis of surrounding tissue) to the BBB; mechanical obstruction of microvessels by parasitized red blood cells, leukocytes, or platelets; overproduction of cytokines that degrade tight junction proteins; or microbe-specific interactions with the BBB that facilitate transcellular passage of the microorganism. The microorganisms that cause CNS infections include a wide range of bacteria, mycobacteria, yeasts, fungi, viruses, spirochaetes (e.g., neurosyphilis), and parasites (e.g., cerebral malaria and strongyloidiasis). The clinical picture of the various infections can be nonspecific or characterized by distinct, recognizable clinical syndromes. At some juncture, individuals with severe acute CNS infections require critical care management that warrants neuro-ICU admission. The implications for CNS infections are serious and complex and include the increased human and material resources necessary to manage very sick patients, the difficulties in triaging patients with vague or mild symptoms, and ascertaining the precise cause and degree of CNS involvement at the time of admission to the neuro-ICU. This chapter addresses a wide range of severe CNS infections that are better managed in the neuro-ICU. Topics covered include the medical epidemiology of the respective CNS infection; discussions of the relevant neuroanatomy and blood supply (essential for understanding the pathogenesis of CNS infections) and pathophysiology; symptoms and signs; diagnostic procedures, including essential neuroimaging studies; therapeutic options, including empirical therapy where indicated; and the perennial issue of the utility and effectiveness of steroid therapy for certain CNS infections. Finally, therapeutic options and alternatives are discussed, including the choices of antimicrobial agents best able to cross the BBB, supportive therapy, and prognosis.

Rocky Mountain spotted fever in children

Rocky Mountain spotted fever is typically undifferentiated from many other infections in the first few days of illness. Treatment should not be delayed pending confirmation of infection when Rocky Mountain spotted fever is suspected. Doxycycline is the drug of choice even for infants and children less than 8 years old.

Association between sepsis and Rocky Mountain spotted fever

Rocky Mountain spotted fever (RMSF) is a disease caused by the Gram-negative coccobacillus Rickettsia ricketsii which has been on the rise since the last decade in the USA. The symptoms are common to the many viral diseases, and the classic triad of fever, rash and headache is not always present when RMSF is diagnosed. It may progress to severe cases such as renal failure, disseminated intravascular coagulation and septicaemia. This report aims to present a fulminant case of RMSF associated with sepsis. It describes a female patient's case that quickly progressed to sepsis and death. The patient showed non-specific symptoms for 5 days before being admitted to a hospital. The fact that she lived in an area highly infested with Amblyomma aureolatum ticks was unknown to the medical staff until the moment she died.

Assessment of real-time PCR assay for detection of Rickettsia spp. and Rickettsia rickettsii in banked clinical samples

Two novel real-time PCR assays were developed for the detection of Rickettsia spp. One assay detects all tested Rickettsia spp.; the other is specific for Rickettsia rickettsii. Evaluation using DNA from human blood and tissue samples showed both assays to be more sensitive than nested PCR assays currently in use at the CDC.

Unusual bacterial infections and the pleura

Rickettsiosis, Q fever, tularemia, and anthrax are all bacterial diseases that can affect the pleura. Rocky Mountain Spotted Fever (RMSF) and Mediterranean Spotted Fever (MSF) are caused by Rickettsia rickettsii and Rickettsia conorii, respectively. Pleural fluid from a patient with MSF had a neutrophil-predominant exudate. Coxiellaburnetii is the causative agent of Q fever. Of the two cases described in the literature, one was an exudate with a marked eosinophilia while the other case was a transudate due to a constrictive pericarditis. Francisella tularensis is the causative agent of tularemia. Pleural fluid from three tularemia patients showed a lymphocyte predominant exudate. Bacillusanthracis is the causative agent of anthrax. Cases of inhalational anthrax from a recent bioterrorist attack evidenced the presence of a serosanguineous exudative pleural effusion. These four bacterial microorganisms should be suspected in patients presenting with a clinical history, exposure to known risk factors and an unexplained pleural effusion.

Q Fever with unusual exposure history: a classic presentation of a commonly misdiagnosed disease

We describe the case of a man presumptively diagnosed and treated for Rocky Mountain spotted fever following exposure to multiple ticks while riding horses. The laboratory testing of acute and convalescent serum specimens led to laboratory confirmation of acute Q fever as the etiology. This case represents a potential tickborne transmission of Coxiella burnetii and highlights the importance of considering Q fever as a possible diagnosis following tick exposures.

Travel-associated skin disease

Travel associated skin disease is extremely common and a frequent cause of the returning traveller seeking medical attention. Widespread cutaneous eruptions usually represent reactive rashes, indicating an underlying systemic infection or allergic reaction. Patients with disseminated or spreading rashes following travel often present with fever and malaise. In contrast, those presenting with localised skin disease such as a blister, nodule, plaque, ulcer etc are usually well in themselves but have sustained a bite/sting/penetrating injury or introduction of infection directly into the skin at the affected site. As a general rule widespread rashes are investigated with blood tests/serology and localised lesions with a skin biopsy for culture and histology.

Life-threatening ANCA-positive vasculitis associated with rickettsial infection

We present a 47-year-old Caucasian fire fighter who developed multisystem organ failure in the setting of a positive antineutrophil cytoplasmic autoantibody (myeloperoxidase) as well as confirmed Rocky Mountain spotted fever by skin biopsy PCR. This case provided a diagnostic challenge, a rare association of a Rickettsia infection and autoimmune vasculitis as well as a unique management approach.

Trends in clinical diagnoses of Rocky Mountain spotted fever among American Indians, 2001-2008

American Indians are at greater risk for Rocky Mountain spotted fever (RMSF) than the general U.S. population. The epidemiology of RMSF among American Indians was examined by using Indian Health Service inpatient and outpatient records with an RMSF International Classification of Diseases, Ninth Revision, Clinical Modification diagnosis. For 2001-2008, 958 American Indian patients with clinical diagnoses of RMSF were reported. The average annual RMSF incidence was 94.6 per 1,000,000 persons, with a significant increasing incidence trend from 24.2 in 2001 to 139.4 in 2008 (P = 0.006). Most (89%) RMSF hospital visits occurred in the Southern Plains and Southwest regions, where the average annual incidence rates were 277.2 and 49.4, respectively. Only the Southwest region had a significant increasing incidence trend (P = 0.005), likely linked to the emergence of brown dog ticks as an RMSF vector in eastern Arizona. It is important to continue monitoring RMSF infection to inform public health interventions that target RMSF reduction in high-risk populations.