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Background: Brazilian spotted fever is a tick-borne disease caused by the bacterium Rickettsia rickettsii, whose main vector in Brazil is the tick Amblyomma sculptum. Amplifying hosts are essential for the perpetuation of this bacterium in the tick population as they can be sources of infection during bacteremic periods. Recent studies demonstrated the ability of suids (Sus scrofa) to sustain populations of A. sculptum, one of the main tick species found parasitizing wild boars in the midwestern and southeastern regions of Brazil. In this study, wild boars were experimentally infected with R. rickettsii by tick infestation and were evaluated for their ability to transmit the infection to A. sculptum ticks, under laboratory conditions., Methods: Four wild boars were infected with R. rickettsii through infestation with R. rickettsii-infected A. sculptum adults (infected group); a fifth wild boar was infested with uninfected A. sculptum adults (control group). Simultaneously, the animals were infested with uninfected larvae and nymphs of A. sculptum. The wild boars were monitored for 28 days by clinical examination and hematological tests, real-time quantitative PCR (qPCR) of blood for the detection of Rickettsia and inoculation of blood in guinea pigs. IgG antibody titers were followed until the end of the experiment. Unfed nymphs and adults, molted from engorged larvae and nymphs that fed on wild boars, were used to infest susceptible guinea pigs and rabbits; some of these unfed ticks were tested by qPCR for rickettsial detection., Results: The wild boars showed no clinical or hematological alterations, and bacteremia was not detected by qPCR or inoculation of wild boar blood into guinea pigs. Furthermore, wild boars showed a moderate humoral response, with anti-R. rickettsii endpoint titers up to 256 or 512. Rickettsial DNA was not detected in molted ticks after acquisition feeding on wild boars. Moreover, no disease or seroconversion was observed in guinea pigs and rabbits that were infested with ticks originated from wild boar acquisition feeding., Conclusions: Wild boars seroconverted to Rickettsia spp. after being infested with R. rickettsii-infected A. sculptum; however, they did not develop bacteremia and did not act as competent amplifying hosts of R. rickettsii for A. sculptum ticks., Competing Interests: Declarations. Ethics approval and consent to participate: This study was approved by the Ethics Committee of Animal Use of the University of São Paulo (CEUA/USP project no. 8651010623) and Ethics Committee of Animal Use of the Federal University of Goiás (CEUA/UFG project no. 076/21). Consent for publication: Not applicable. Competing interests: The authors declare no competing interests., (© 2024. The Author(s).)

Since 1996, the incidence of rickettsiosis has been increasing in Yucatán, Mexico, but recent prevalence data are lacking. This study aimed to determine exposure to the Spotted Fever Group (SFG) and Typhus Group (TG) in human serum samples suspected of tick-borne diseases (TBD) between 2015 and 2022. A total of 620 samples were analysed using indirect immunofluorescence assay (IFA) to detect IgG antibodies against SFG ( Rickettsia rickettsii ) and TG ( Rickettsia typhi ), considering a titer of ≥64 as positive. Results showed that 103 samples (17%) were positive for R. rickettsii and 145 (24%) for R. typhi , while 256 (41%) and 229 (37%) were negative, respectively. There was a cross-reaction in 244 samples (39%). Individuals with contact with vectors, such as ticks, showed significant exposure to fleas (p = 0.0010). The study suggests a high prevalence of rickettsiosis and recommends prospective studies to assess the disease burden and strengthen surveillance and prevention in Yucatán, considering factors like temperature and ecological changes.

Rocky Mountain spotted fever (RMSF) is a tickborne disease endemic in areas of the Americas. Persistent high incidence of the disease exists in northern Mexico, perpetuated by local populations of brown dog ticks (Rhipicephalus sanguineus sensu lato) and free-roaming dogs. Six cases of RMSF caused by Rickettsia rickettsii, including three deaths, were reported to the California Department of Public Health during July 2023-January 2024. All six patients were eventually determined to have had exposure to R. rickettsii in Tecate, Mexico, a municipality on the U.S. border that had not been previously described as a high-risk RMSF area. Identification and reporting of the cases were complicated by challenges in diagnosis. The serious nature of the disease and delays in initiating appropriate treatment can result in life-threatening consequences. Epidemiologic collaborations among local, state, federal, and international public health agencies were essential to identifying Tecate as the location of exposure. Further collaborations will be important for directing future prevention measures. Increased health care provider awareness of RMSF is critical on both sides of the border to facilitate earlier diagnosis and initiation of appropriate treatment., Competing Interests: All authors have completed and submitted the International Committee of Medical Journal Editors form for disclosure of potential conflicts of interest. No potential conflicts of interest were disclosed.

Rocky mountain spotted fever (RMSF) causes significant illness and death in children. Although historically rare in California, USA, RMSF is endemic in areas of northern Mexico that border California. We describe 7 children with RMSF who were hospitalized at a tertiary pediatric referral center in California during 2017-2023. Five children had recent travel to Mexico with presumptive exposure, but 2 children did not report any travel outside of California. In all 7 patients, Rickettsia rickettsii DNA was detected by plasma microbial cell-free next-generation sequencing, which may be a useful diagnostic modality for RMSF, especially early in the course of illness, when standard diagnostic tests for RMSF are of limited sensitivity. A high index of suspicion and awareness of local epidemiologic trends remain most critical to recognizing the clinical syndrome of RMSF and initiating appropriate antimicrobial therapy in a timely fashion.

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., (© 2023. The Author(s), under exclusive licence to Springer Nature Switzerland AG.)

Brazilian spotted fever (BSF) is a highly lethal disease caused by Rickettsia spp. and is transmitted by ticks of the genus Amblyomma. Understanding the epidemiology of BSF in each region can help direct health surveillance actions. The objective of this study was to determine the spatial distribution of vectors and the incidence of BSF in the state of São Paulo. Spatial analysis included confirmed BSF cases between 2009 and 2019; occurrences were registered by municipalities of the state. There were 752 confirmed BSF cases, with incidences ranging between 0.01 and 10.37/10,000 inhabitants. Moran's Global Index for BSF was 0.20 (p = .001), which was indicative of spatial dependence. Moran's map located a cluster of 20 high priority municipalities for BSF and showed that Amblyomma sculptum is the vector involved in Rickettsia rickettsii transmission in these locations. Spatial analysis identified clusters formed by 47, 20 and seven significant municipalities for the presence of A. sculptum, Amblyomma aureolatum and Amblyomma ovale vectors, respectively. Surveillance and prevention actions are necessary in areas that are at high risk for BSF and in areas where the presence of vectors was significant., (© 2020 Blackwell Verlag GmbH.)

For the last decade, the New Jersey (NJ) Department of Health has reported between 42 and 144 new cases each year of "spotted fever group rickettsiosis" (SFGR), a statistic that reflects uncertainty regarding which rickettsial agents (Proteobacteria: Rickettsiaceae: Rickettsia ) are infecting NJ residents. To identify the Rickettsia circulating in NJ ticks, we used a combination of conventional and real time PCR approaches to screen 560 Dermacentor variabilis Say and 245 Amblyomma americanum L. obtained from a 1-day state-wide surveillance in May 2018 and an additional 394 D. variabilis collected across NJ in 2013-2018. We found zero D. variabilis infected with Rickettsia rickettsii, the agent of Rocky Mountain spotted fever and, on average, 1.3% infected with presumed nonpathogenic Rickettsia montanensis . We also found zero A. americanum infected with R. rickettsii, and 20% infected with Rickettsia amblyommatis, a prevalence somewhat lower than in more southern states. Overall, we conclude that it is unlikely that R. rickettsii vectored by D. variabilis is a primary cause of SFGR cases in NJ and discuss our findings in the context of known facts and current limitations. We conclude that understanding the causes of SFGR east of the Mississippi will require collaboration among medical doctors, public health authorities, and medical entomologists to follow up presumptive human cases of SFGR with detailed histories of exposure, species-specific molecular assays, and active surveillance of putative vectors and the pathogens they may carry.

Brazilian spotted fever (BSF) is a highly lethal disease in southeastern Brazil. BSF is caused by the bacterium Rickettsia rickettsii and is transmitted by the bites of the tick of the genus Amblyomma. The spatial distribution of BSF risk areas is not well known in the country given the complexity of the transmission cycle. This study used the ecological niche modeling (ENM) approach to anticipate the potential distribution of the etiological agent (Rickettsia rickettsii), vectors (Amblyomma sculptum and A. dubitatum), and hosts (Hydrochoerus hydrochaeris, Didelphis aurita, and D. marsupialis) of BSF in Brazil. We compiled occurrence records for all vectors, hosts, and BSF from our own field surveillance, online repositories, and literature. ENM identified BSF risk areas in southeastern and southern Brazil, and anticipated other dispersed suitable areas in the western, central, and northeastern coast regions of Brazil. Tick vectors and mammalian hosts were confined to these same areas; however, host species showed broader suitability in northern Brazil. All species ENMs performed significantly better than random expectations. We also tested the BSF prediction based on 253 additional independent cases identified in our surveillance; the model anticipated 251 out of 253 of these independent cases. Background similarity tests comparing the ENMs of R. rickettsii, tick vectors, and mammalian hosts were unable to reject null hypotheses of niche similarity. Finally, we observed close coincidence between independent BSF cases, and areas suitable for combinations of vectors and hosts, reflecting the ability of these model pairs to anticipate the distribution of BSF cases across Brazil., (Copyright © 2020 Elsevier B.V. All rights reserved.)

Background: The Cumberland Gap Region (CGR) of the United States is a natural corridor between the southeastern, northeastern, and midwestern regions of the country. CGR has also many species of ticks and mosquitos that serve as competent vectors for important animal and human pathogens. In this study, we tested dogs from six different animal shelters in the CGR for Rocky Mountain spotted fever (RMSF), anaplasmosis, Lyme disease, canine ehrlichiosis and canine heartworm disease., Results: Sera from 157 shelter dogs were tested for antibodies to RMSF agent, Rickettsia rickettsii, using an indirect immunofluorescence assay. Sixty-six dogs (42.0%) were positive for either IgM or IgG, or both IgM and IgG antibodies to R. rickettsii. Moreover, the same set of sera (n = 157) plus an and additional sera (n = 75) from resident dogs at the same shelters were tested using the SNAP 4Dx Plus. Of 232 dogs tested, two (0.9%) were positive for antibodies to Anaplasma phagocytophilum/A. platys, nine (3.9%) were positive for antibodies to Borrelia burgdorferi, 23 (9.9%) for positive for antibodies to Ehrlichia canis/E. ewingii, and 13 (5.6%) were positive for Dirofilaria immitis antigen. Co-infection with two or more etiologic agents was detected in five animals. Three dogs had antibodies to both B. burgdorferi and E. canis/E. ewingii, and two dogs were positive for D. immitis antigen and antibodies to B. burgdorferi and E. canis/E. ewingii., Conclusions: Shelter dogs in the CGR are exposed to a number of important vector-borne pathogens. Further studies are required to ascertain the roles these animals play in maintenance and transmission of these pathogens.

Tick-borne rickettsiae are undergoing epidemiological changes in the eastern United States while human encounters with lone star ticks (Amblyomma americanum L.) have increased substantially. We used real-time polymerase chain reaction assays to test for three species of spotted fever group rickettsiae (SFGR) (Rickettsiales: Rickettsiaceae) in 1,858 nymphal A. americanum collected from Monmouth County, New Jersey, a coastal county with endemic Lyme disease and established tick surveillance. Out of the 1,858 tested, 465 (25.0%) were infected with Rickettsia amblyommatis Karpathy, a species of undetermined pathogenicity found frequently in A. americanum, while 1/1,858 (0.05%) contained Rickettsia rickettsii Brumpt, the agent of Rocky Mountain spotted fever. No ticks tested positive for mildly pathogenic Rickettsia parkeri Lackman, and no ticks were co-infected with multiple Rickettsia spp. Our results indicate that A. americanum could be involved in transmission of R. rickettsii to humans in New Jersey, albeit rarely. The much higher rates of R. amblyommatis infection are consistent with hypotheses that human sera reacting to this species could contribute to reports of mild SFGR cases., (© The Author(s) 2020. Published by Oxford University Press on behalf of Entomological Society of America. All rights reserved. For permissions, please e-mail: journals.permissions@oup.com.)

Zoonotic tick-borne diseases, including those caused by Rickettsia species, continue to have serious consequences for public health worldwide. One such disease that has emerged as a major problem in several countries of the American continent is the Rocky Mountain Spotted Fever (RMSF) caused by the bacterium Rickettsia rickettsii. Several tick species are capable of transmitting R. rickettsia, including Amblyomma cajennense, A. aureolatum, A. imitator, Rhipicephalus sanguineus, Dermacentor andersoni, D. variabilis and possibly A. americanum. Despite previous reports in Mexico linking new outbreaks of RMSF to the presence of these tick species, no robust measures have tackled transmission. In the present study, we amplified R. rickettsii from 109 test DNA samples extracted from ticks collected from several animals and humans of Tamaulipas, Mexico, between November 2015 and December 2017. Our analysis revealed the presence of R. rickettsii in six samples and these findings contribute to a spatial distribution map that is intended to minimize the risk of transmission to humans.

The bacterium Rickettsia rickettsii is the agent of Brazilian spotted fever (BSF), a highly fatal disease that is transmitted in Brazil mainly by the tick Amblyomma sculptum Berlese, which uses capybaras (Hydrochoerus hydrochaeris Linnaeus) as major hosts. In 2015, we captured nine capybaras in a BSF-endemic area of southeastern Brazil. From each capybara, we collected blood sera that were tested through the immunofluorescence assay using Rickettsia spp. antigens, and A. sculptum ticks, processed for isolation of R. rickettsii through guinea pig inoculation. All capybaras (100%) were seroreactive to Rickettsia spp., with highest titers to R. rickettsii. A total of 166 A. sculptum ticks were macerated and inoculated into nine guinea pigs, from which only one presented high fever and seroconverted to R. rickettsii. Blood from this febrile animal was inoculated into additional guinea pigs (guinea pig passages), which also became febrile and seroconverted, or when euthanized during the fever period, their internal organs (spleen, lung) were shown to contain R. rickettsii DNA. The present rickettsial isolate has been maintained cryopreserved as infected guinea pig organs. There was at least one R. rickettsii-infected tick among the 166 macerated ticks, giving a minimal infection rate of 0.6% (1/166). This infection rate is within the range of previous studies, which reported that only 0.05% to at most 1.28% A. sculptum ticks were infected by R. rickettsii in other BSF-endemic areas. These low infection rates support the low incidence of BSF, despite of A. sculptum being the most frequent human-biting tick in southeastern Brazil., (© The Author(s) 2019. Published by Oxford University Press on behalf of Entomological Society of America. All rights reserved. For permissions, please e-mail: journals.permissions@oup.com.)

We report a fatal case of Rocky Mountain spotted fever (RMSF) in a man in Brazil without recent history of tick bites or environmental exposure. He received an accidental needlestick while working as a nurse. The nurse and his patient died. Both cases were confirmed as RMSF by molecular methods.

The bacterium Rickettsia rickettsii causes Brazilian spotted fever (BSF), a highly lethal disease that is transmitted by Amblyomma sculptum ticks in areas where capybaras ( Hydrochoerus hydrochaeris ) are the tick's major hosts. In this study, we evaluated the expansion of a capybara population in a residential park in São Paulo state, and the implications of such expansion to the occurrence of ticks and BSF. The capybara population was quantified during 2004-2013. In 2012, there was a BSF human case in the area, culminating in the complete fencing of the residential park and the official culling of all capybaras. Quantification of ticks in the environment was performed by dry ice traps from 2005 to 2018. Domestic dogs in 2006-2011 and capybaras in 2012 were serologically tested for the presence of anti- R. rickettsii antibodies. Our results show that capybara numbers increased ≈5 times from 2004 (41 capybaras) to 2012 (230 capybaras). Dry ice traps collected A. sculptum and Amblyomma dubitatum. The number of A. dubitatum adult ticks was generally higher than A. sculptum adults during 2005-2006; however, during 2012-2013, A. sculptum outnumbered A. dubitatum by a large difference. During 2016-2018 (after capybara culling), the number of both species fell close to zero. The low numbers of A. sculptum adult ticks during 2005-2006 coincided with relatively low capybara numbers (<80). Thereafter, in 2012, we counted the highest numbers of both A. sculptum ticks and capybaras (230 animals). All 40 canine blood samples were seronegative to R. rickettsii , in contrast to the 48.3% seropositivity (83/172) among capybaras. Our results support that the emergence of BSF in the residential park was a consequence of the increase of the local capybara population, which in turn, provided the increment of the A. sculptum population. Culling the entire capybara population eliminated the risks of new BSF cases.

Background: Brazilian spotted fever (BSF), caused by the bacterium Rickettsia rickettsii, has been associated with the transmission by the tick Amblyomma sculptum, and one of its main hosts, the capybara (Hydrochoerus hydrochaeris)., Methods: During 2015-2019, we captured capybaras and ticks in seven highly anthropic areas of São Paulo state (three endemic and four nonendemic for BSF) and in two natural areas of the Pantanal biome, all with established populations of capybaras., Results: The BSF-endemic areas were characterized by much higher tick burdens on both capybaras and in the environment, when compared to the BSF-nonendemic areas. Only two tick species (A. sculptum and Amblyomma dubitatum) were found in the anthropic areas; however, with a great predominance of A. sculptum (≈90% of all ticks) in the endemic areas, in contrast to a slight predominance of A. dubitatum (≈60%) in the nonendemic areas. Tick species richness was higher in the natural areas, where six species were found, albeit with a predominance of A. sculptum (≈95% of all ticks) and environmental tick burdens much lower than in the anthropic areas. The BSF-endemic areas were characterized by overgrowth populations of A. sculptum that were sustained chiefly by capybaras, and decreased populations of A. dubitatum. In contrast, the BSF-nonendemic areas with landscape similar to the endemic areas differed by having lower tick burdens and a slight predominance of A. dubitatum over A.sculptum, both sustained chiefly by capybaras. While multiple medium- to large-sized mammals have been incriminated as important hosts for A. sculptum in the natural areas, the capybara was the only important host for this tick in the anthropic areas., Conclusions: The uneven distribution of R. rickettsii infection among A. sculptum populations in highly anthropic areas of São Paulo state could be related to the tick population size and its proportion to sympatric A. dubitatum populations., Competing Interests: The authors have declared that no competing interests exist.

The study of rickettsial agents associated with ticks from wild felines is scarce. In Europe, three species of Rickettsia have been detected (Rickettsia helvetica, Rickettsia massiliae, and Rickettsia monacensis) in ticks collected from the Iberian lynx (Lynx pardinus). However, no studies have been conducted on another lynx species. For this reason, the aim of this study was to identify the diversity of Rickettsia species in ticks associated with bobcats (Lynx rufus) collected in the State of Tamaulipas, Mexico. During 1999 and 2004, nine bobcats from two municipalities of the state were trapped and visually inspected for the presence of ticks. A total of 95 ticks were collected from these lynxes. Ticks were preserved in 96% ethanol. Subsequently we identified the presence of Rickettsia DNA by the amplification of several fragments of genes 17 kDa, ompA and ompB. Recovered sequences were concatenated, aligned, and compared with those of reference deposited in GenBank. Additionally, a phylogenetic analysis was performed using the Maximum Likelihood method. The ticks were morphologically identified as belonging to the species Dermacentor variabilis. We selected a subset of 60 ticks which were examined, and 5% (3/60) were positive with an identity of 99% to sequences of R. rickettsii deposited in GenBank. The results obtained represent the first record of R. rickettsii in ticks associated with wild carnivores, and in particular with bobcats distributed in northeast of Mexico., (Copyright © 2019 Elsevier GmbH. All rights reserved.)

Capybaras (Hydrochoerus hydrochaeris Linnaeus, 1766) (Rodentia: Caviidae) are important hosts of Amblyomma ticks (Acari: Ixodidae), which in turn can transmit rickettsiae to humans and animals. However, there is a scarcity of studies about the tick fauna and rickettsial infection in the Amazon region. The present study evaluated rickettsial infection in capybaras and ticks in different areas of the municipality of Rio Branco, state of Acre, in the Western Brazilian Amazon, where rickettsiosis has never been reported. Blood sera from 43 capybaras from four localities in Rio Branco were tested by indirect immunofluorescence assay using Rickettsia rickettsii antigens. Ticks were collected from capybaras and from vegetation as well. Ticks were taxonomically identified to the species level and some of them were tested by PCR, targeting a fragment of the rickettsial gltA gene. Additionally, ticks were tested for bacteria from the genus Borrelia and family Anaplasmatacae. All capybaras submitted to the serological examination were considered non-reactive to R. rickettsii. A total of 410 ticks were collected directly from the capybaras. Amblyomma dubitatum Neumann, 1899 was the most abundant species (82.4%), followed by Amblyomma naponense (Packard, 1869) (14.3%), Amblyomma humerale Koch, 1844 (0.7%), Amblyomma pacae Aragão, 1911 (0.4%), Amblyomma rotundatum Koch 1844 (0.2%) and Amblyomma sp. (1.7%). From the environment 262 ticks were collected: Rhipicephalus microplus (Canestrini, 1888) (88.9%), Dermacentor nitens Neumann, 1897 (9.9%), Amblyomma varium Koch, 1844 (0.7%) and A. rotundatum (0.3%). With the exception of A. humerale, A. rotundatum and R. microplus, all other species are reported here for the first time in the state. Some of the ticks sampled (N = 317) were tested by molecular methods for infection by Rickettsia spp. Rickettsia bellii was identified infecting A. dubitatum and A. rotundatum, while Rickettsia amblyommatis only was found infecting A. humerale and Rickettsia sp. strain Tapirapé was found in A. naponense. This is the first detection of R. bellii and Rickettsia sp. strain Tapirapé in Acre. No Borrelia or Anaplasmataceae were found in the tested ticks. These results add relevant knowledge about the Rickettsia spp. and the acarological fauna in the region of the Western Amazon, and are essential for the maintenance of vigilance about possible pathogens that occur in the state and determination of the risks that they pose to humans and animals that inhabit the region., (Copyright © 2019 Elsevier GmbH. All rights reserved.)

This report describes a new lethal case of Rickettsia rickettsii infection in a child from Northwestern Colombia, after ten years of the last outbreaks in the same region. Colombian public-health authorities should consider to include this severe rickettsiosis in the compulsory-reporting diseases, with the aim of knowing its burden in the country., (Copyright © 2019 Elsevier GmbH. All rights reserved.)

An epidemic of Rocky Mountain spotted fever (RMSF) is ongoing in Mexicali, México. We visited 100 neighborhoods with diagnosed human cases and 100 control neighborhoods to evaluate knowledge of the epidemic; obtain data on the spatial distribution of dogs, canine seroprevalence and active infection, tick infestations, and presence of rickettsial DNA in ticks; and evaluate risk factors for human cases, seropositivity, and tick infestation within an unbiased study design. The majority (80%) of residents had heard of RMSF, but only 48% used acaricides in the home or on dogs. Case neighborhoods and those with high canine seroprevalence tended to be on the city periphery or in the agricultural valley. No dogs were polymerase chain reaction (PCR) positive for Rickettsia rickettsii , and the overall seroprevalence was 65% (titers from 64 to 1,024). PCR prevalence in ticks was 0.70%, confirmed by DNA sequencing as R. rickettsii ; neighborhood prevalence ranged from 0.7% to 6.1%. Twelve percent of dogs had high tick burdens, and all ticks were Rhipicephalus sanguineus . Epidemiologically significant risk factors were ground covering for a neighborhood having a human case; dogs having poor body condition and weighing < 10 kg for canine seropositivity; dogs living at the home for the number of ticks in the environment; and being near canals, having trash on the patio, and a dog being thin for tick burdens on dogs. A One Health approach is crucial to understanding RMSF and brown dog ticks.

Introduction: The species of the Amblyoma cajennense complex, potential vectors involved in the transmission of Rickettsia rickettsii in Central and South America, have a wide geographical distribution in the Neotropics. In Colombia, the knowledge about these species, their distribution, and many aspects of their ecology is still limited. Objective: To explore the ecology of A. cajennense complex in Colombia based on the study of its habitat selection, as well as the generation of potential geographic and climatic distribution models. Materials and methods: We used unique records of these ticks to study the selection patterns of the climatic habitat using the Ecological Niche Factor Analysis (ENFA), and we built distribution models using the MaxEnt and GARP algorithms. Results: The record of distributions showed that A. cajennense complex is present in all five natural regions of Colombia with 64.71% of the records found in the departments of Antioquia, Cundinamarca, and Huila. The analysis of their habitat selection showed that these ticks preferably select geographical areas (ENFA: 96.03%) according to the isothermality conditions and the precipitation of the driest quarter of the year. The potential distribution models indicated habitat suitability in 31 to 51% of the area of the country depending on the algorithm. Conclusions: The distribution of A. cajennense complex in Colombia is highly influenced by a climatebased habitat selection, a characteristic that favored the creation of distribution models. Field studies will allow the validation of the potential distribution models and further genetic studies will be required in the country to identify species within the complex and study their potential hybridization areas.

Objectives: Rickettsia rickettsii is the causative agent of Rocky Mountain spotted fever, which is the most severe spotted fever group (SFG) rickettsiosis. Developing a simple and reliable detection method is required., Methods: A detection method for R. rickettsii was established based on a recombinase polymerase amplification (RPA) assay and the lateral flow (LF) test. A specific target sequence was screened, and corresponding primers and probes were designed, synthesized, and screened for establishing an RPA assay with high amplification efficiency. Reagent concentrations, amplification time, and loading volume for strip development were optimized. The detection limit, analytic sensitivity and specificity were evaluated., Results: A rapid, visual, sensitive and specific method for the detection of R. rickettsii based on RPA and the LF test was successfully established. The novel method had a limit of detection of 10 to 50 copies/reaction without recognizing other organisms. Analytical sensitivity and specificity were ≥90% and 100%, respectively, as evaluated by animal and simulative human samples., Conclusions: Using the established method, detection could be completed in 30 min with visually detectable results by the naked eye, without requirement of any instrument except a constant temperature equipment. The technique shows superior detection performance and is promising for wide use in the field as well as resource-limited areas for R. rickettsii detection., Competing Interests: The authors have declared that no competing interests exist.

Since 2008, a large epidemic of Rocky Mountain spotted fever has been emerging among humans and dogs in Mexicali, adjacent to the United States in Baja California, Mexico. We molecularly confirmed the causative agent; this information can be used to study the origin and dynamics of the epidemic.

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.

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.

Although Espírito Santo state is considered an endemic area for Brazilian spotted fever (BSF) with related lethal cases, it also constitutes the only state of southeastern Brazil that currently lacks a specific confirmation of the specific rickettsial agent. In an attempt to a species level confirmation of the etiological agent of fatal rickettsiosis cases in Espírito Santo state, in this study we tested human sera obtained between 2015 to 2017 by means of qPCR and subsequent conventional PCR protocols targeting gltA (citrate synthase) and ompA (190-kDA outer membrane protein) rickettsial genes. All samples were found to contain rickettsial DNA through the citrate synthase qPCR protocol. By conventional PCR, rickettsial gltA and ompA specific DNA fragments were detected in 25% (one sample) and 50% (2 samples) of the screened sera, respectively. Obtained consensuses for each gene partial sequences were 100% identical to Rickettsia rickettsii gltA and ompA genes. The present study confirms for the first time R. rickettsii as the etiological agent of a lethal spotted fever group rickettsiosis in human patients from Espírito Santo state., (Copyright © 2018 Elsevier GmbH. All rights reserved.)

Spotted fever is a rare acute and multisystemic febrile infectious disease with a mortality rate of ≥50% without adequate antibiotic treatment, and in diagnosed and treated cases, of approximately 2.5%. Currently, the applied test to diagnose this disease is the indirect immunofluorescence reaction, however two samples of paired sera are necessary to confirm the diagnosis, since using only one sample may allow for confusion with cross reactions. OmpA is an outer membrane protein present in the R. rickettsia, the etiological agent of spotted fever, able to activate dendritic and macrophage cells. It also presents immunogenicity properties, and is considered a target for the development of diagnostic tests for spotted fever. In this context, an amperometric immunosensor was developed for the identification of sera antibodies (human IgG) from patients with spotted fever aimed at improving sensitivity and minimize sample volume. The development of the immunosensor was conducted using a synthetic peptide, derivative from the H6PGA4 R. rickettsia protein, homologous to OmpA. Amperometric responses were generated at -0.6 to 0.6V, at a scan rate of 0.025Vs -1 for 20 cycles, a limit of detection of approximately 10ngmL -1 for the synthetic peptides and 0.01µgmL -1 for the humam serum, a sensitivity of 2.59µA, adequate for the detection of spotted fever antibodies. The construction of this immunosensor, capable of identifying circulating antibodies in real time, can also be applied in the diagnosis of other infectious-parasitic diseases., (Copyright © 2017 Elsevier B.V. All rights reserved.)

Introducción: La fiebre manchada de las montañas rocosas (FMMR) es causada por Rickettsia rickettsii. En Coahuila, la región de la Comarca Lagunera se considera una zona endémica. No se han reportado casos en la zona sur del estado, específicamente en la ciudad de Saltillo., Métodos: Estudio prospectivo, reporte de casos. Se incluyeron los casos de niños atendidos en el Hospital del Niño Dr. Federico Gómez Santos en la ciudad de Saltillo, Coah., del mes de septiembre de 2012 a septiembre 2017 con diagnóstico confirmado clínicamente y por reacción en cadena de la polimerasa (PCR) de FMMR. Se presentan los antecedentes epidemiológicos, las características clínicas y evolución de los pacientes., Resultados: Se confirmaron 14 pacientes. La relación masculino:femenino fue de 1.8:1, la edad promedio de los pacientes fue de 7.6 años (18 meses a 13 años). El 42.8% de los pacientes refirió el contacto con perros y el 57.1% afirmó tener contacto con garrapatas. En todos los casos hubo fiebre y exantema purpúrico; alrededor del 70% manifestaron mialgias y artralgias; el 28% tuvo sangrado del tubo digestivo, y el 11% alteraciones neurológicas graves. El 64.2% de los casos recibió tratamiento adecuado con doxiciclina. Fallecieron 8 pacientes, con una tasa de letalidad de 57.1%., Conclusiones: La zona sur de Coahuila debe considerarse una zona endémica para FMMR. El retraso en el diagnóstico y tratamiento favorecen una mayor letalidad., Background: Rocky Mountain Spotted Fever (RMSF) is caused by Rickettsia rickettsii. In Coahuila, Comarca Lagunera is considered an endemic zone; no cases have been reported in the southern zone of the state, specifically in the city of ­Saltillo., Methods: Prospective study, cases report. Children evaluated in the Hospital del Niño Dr. Federico Gómez Santos from September 2012 to September 2017, with clinically and laboratory (by polymerase chain reaction, PCR) confirmed diagnosis of FMMR were included. The epidemiological antecedents, clinical characteristics and patient’s evolution are presented., Results: 14 patients were confirmed. The male: female ratio was 1.8: 1, the average age of the patients was 7.6 years (18 months to 13 years). 42.8% reported contact with dogs and 57.1% confirmed contact with ticks. In all cases, there was fever and purpuric rash; around 70% manifested myalgias and arthralgias; 28% presented digestive tract bleeding and 11% had severe neurological alterations. 64.2% of the cases received adequate treatment with doxycycline. Eight patients died with a case fatality rate of 57.1%., Conclusions: The southern zone of Coahuila should be considered an endemic area for FMMR. The delay in diagnosis and treatment favor a greater lethality., (Copyright: © 2018 SecretarÍa de Salud.)

Background: As there is little data on vector-borne diseases of cats in the Caribbean region and even around the world, we tested feral cats from St Kitts by PCR to detect infections with Babesia, Ehrlichia and spotted fever group Rickettsia (SFGR) and surveyed them for antibodies to Rickettsia rickettsii and Ehrlichia canis., Results: Whole blood was collected from apparently healthy feral cats during spay/ neuter campaigns on St Kitts in 2011 (N = 68) and 2014 (N = 52). Sera from the 52 cats from 2014 were used to detect antibodies to Ehrlichia canis and Rickettsia rickettsii using indirect fluorescent antibody tests and DNA extracted from whole blood of a total of 119 cats (68 from 2011, and 51 from 2014) was used for PCRs for Babesia, Ehrlichia and Rickettsia. We could not amplify DNA of SFG Rickettsia in any of the samples but found DNA of E. canis in 5% (6/119), Babesia vogeli in 13% (15/119), Babesia gibsoni in 4% (5/119), mixed infections with B. gibsoni and B. vogeli in 3% (3/119), and a poorly characterized Babesia sp. in 1% (1/119). Overall, 10% of the 52 cats we tested by IFA for E. canis were positive while 42% we tested by indirect fluorescent antibody (IFA) for R. rickettsii antigens were positive., Conclusions: Our study provides the first evidence that cats can be infected with B. gibsoni and also indicates that cats in the Caribbean may be commonly exposed to other vector-borne agents including SFGR, E. canis and B. vogeli. Animal health workers should be alerted to the possibility of clinical infections in their patients while public health workers should be alerted to the possibility that zoonotic SFGR are likely circulating in the region.

Rocky Mountain spotted fever (RMSF) is an emerging public health concern near the US-Mexico border, where it has resulted in thousands of cases and hundreds of deaths in the past decade. We identified 4 patients who had acquired RMSF in northern Mexico and subsequently died at US healthcare facilities. Two patients sought care in Mexico before being admitted to US-based hospitals. All patients initially had several nonspecific signs and symptoms, including fever, headache, nausea, vomiting, or myalgia, but deteriorated rapidly without receipt of a tetracycline-class antimicrobial drug. Each patient experienced respiratory failure late in illness. Although transborder cases are not common, early recognition and prompt initiation of appropriate treatment are vital for averting severe illness and death. Clinicians on both sides of the US-Mexico border should consider a diagnosis of RMSF for patients with rapidly progressing febrile illness and recent exposure in northern Mexico.

In Brazil, Spotted Fever (SF) is caused by Rickettsia rickettsii and Rickettsia parkeri strain Atlantic Forest. In recent years, several human cases of a milder SF have been reported from the Maciço de Baturité region of Ceará State. Previous studies in this region found R. parkeri strain Atlantic Forest to be present in Rhipicephalus sanguineus sensu lato and Amblyomma ovale ticks. The present study isolated and identified the Rickettsia spp. present in this new endemic area in Brazil. In March 2015, R. sanguineus s.l. and A. ovale were collected in rural areas of the Maciço de Baturité region, and subjected to the isolation technique. A bacterium was isolated from one R. sanguineus s.l., which phylogenetic analysis clustered to the R. rickettsii group. In conclusion, R. rickettsii bacteria is circulating in the studied area and may in future have an impact on the clinical diagnoses and consequently cause changes in the profile of the disease in the region. In addition, we suggest the increase of epidemiological and environmental surveillance in the area, in order to prevent Brazilian Spotted Fever cases., (Copyright © 2017. Published by Elsevier B.V.)

Background: Brazilian Spotted Fever (BSF), caused by the bacterium Rickettsia rickettsii, is the tick-borne disease that generates the largest number of human deaths in the world. In Brazil, the current increase of BSF human cases has been associated with the presence and expansion of capybaras Hydrochoerus hydrochaeris, which act as primary hosts for the tick Amblyomma sculptum, vector of the R. rickettsii in this area., Methods: We proposed a semi-discrete-time stochastic model to evaluate the role of capybaras in the transmission dynamics of R. rickettsii. Through a sensitivity analysis, we identified the parameters with significant influence on the R. rickettsii establishment. Afterward, we implemented the Gillespie's algorithm to simulate the impact of potential public health interventions to prevent BSF human cases., Results: The introduction of a single infected capybara with at least one infected attached tick is enough to trigger the disease in a non-endemic area. We found that to avoid the formation of new BSF-endemic areas, it is crucial to impede the emigration of capybaras from endemic areas by reducing their birth rate by more than 58%. Model results were corroborated by ex-situ data generated from field studies, and this supports our proposal to prevent BSF human cases by implementing control strategies focused on capybaras., Conclusion: The proposed stochastic model illustrates how strategies for the control and prevention of vector-borne infectious diseases can be focused on amplifier hosts management practices. This work provides a basis for future prevention strategies for other neglected vector-borne diseases.

Rocky Mountain spotted fever, a tick-borne zoonosis caused by Rickettsia rickettsii, is among the most lethal of all infectious diseases in the Americas. In Mexico, the disease was first described during the early 1940s by scientists who carefully documented specific environmental determinants responsible for devastating outbreaks in several communities in the states of Sinaloa, Sonora, Durango, and Coahuila. These investigators also described the pivotal roles of domesticated dogs and Rhipicephalus sanguineus sensu lato (brown dog ticks) as drivers of epidemic levels of Rocky Mountain spotted fever. After several decades of quiescence, the disease re-emerged in Sonora and Baja California during the early 21st century, driven by the same environmental circumstances that perpetuated outbreaks in Mexico during the 1940s. This Review explores the history of Rocky Mountain spotted fever in Mexico, current epidemiology, and the multiple clinical, economic, and social challenges that must be considered in the control and prevention of this life-threatening illness., (Copyright © 2017 Elsevier Ltd. All rights reserved.)

Brazilian Spotted Fever (BSF) is a zoonotic disease caused by the bacterium Rickettsia rickettsii. In the São Paulo Metropolitan Region (SPMR) it is transmitted by Amblyomma aureolatum ticks. In this region, annual lethality of the disease can reach 80% and spatial occurrence depends on environmental factors and more particularly on the presence and interaction of domestic and wild carnivores as well as the presence and characteristics of the remnant Atlantic Rain Forest patches. This study analyzed the association between forest fragmentation and its influence on the risk of occurrence of the disease in the human population. Domestic dogs tested for R. rickettsii antibodies in nine different areas under the influence of different patterns of Rain Forest fragmented landscapes and human occupancy. Landscape metrics were obtained by analyzing satellite images and high-resolution orthophotos. Principal component analysis (PCA) was used to determine among the different landscape variables the one that could best explain the data variance, and the results were tested against canine seroprevalence in order to address disease occurrence risk levels. From 270 canine samples, the seroprevalence ranged from 0 to 37%. PCA showed an inverse correlation between functionally connected large forest patches and the canine seroprevalence for R. rickettsii (p=0.030; Spearman's R=-0.683), while there was a positive correlation between forest border effect and canine seroprevalence (p=0.037; Spearman's R=- 0.909). The further attributed disease occurrence risk level supported the real spatial prevalence of the disease reported for the last eight years (p=0.023; Spearman's R=0.63). The results suggest an important relation of deforestation and fragmentation with the occurrence of BSF in the SPMR., (Copyright © 2016 Elsevier B.V. All rights reserved.)

Relatively little is known about the prevalence of rickettsial species in Dermacentor ticks in eastern Canada. In this study, Dermacentor ticks from the province of Ontario, Canada, were tested for the presence of spotted fever group rickettsial (SFGR) species, Coxiella burnetii and Francisella tularensis. Rickettsia rickettsii was not detected in any ticks tested, but R. montanensis was detected at a prevalence of 2.2% in D. variabilis (17/778). Two other SFGR species, R. parkeri and Candidatus R. andeanae, were detected individually in 2 Amblyomma maculatum ticks. Rickettsia peacockii, a non-pathogenic endosymbiont, was detected in two D. andersonii ticks. Given the highly abundant nature of D. variabilis, surveillance for human pathogens in this species of tick has important public health implications, but the lack of detection of known human pathogens indicates a low risk of infection via this tick species in Ontario. However, the detection of R. parkeri in an adventive A. maculatum tick indicates that health care providers should be aware of the possibility of spotted fever rickettsioses in individuals with a history of travel outside of Ontario and symptoms compatible with a spotted fever rickettsiosis. Coxiella burnetii and Francisella tularensis, human pathogens also potentially transmitted by D. variabilis, were not detected in a subset of the ticks., (Copyright © 2016 Elsevier GmbH. All rights reserved.)

On the fifth day after leaving the Parque Nacional El Rey, province of Salta, Argentina, where she made rural tourism, a woman of Italian origin, aged 47, developed an acute fever followed by a petechial and purpuric rash that progressed rapidly to multiorgan failure. She died on the sixth day after hospitalization. There were references to tick bites and a skin lesion similar to tache noire was found. The autopsy showed generalized vasculitis, ascites, pulmonary edema, acute tubular necrosis and portal centrilobular necrosis. Spleen and liver tissue were processed for PCR Rickettsia spp, based on the detection of the gltA gene. The result was positive. The amplicons obtained were sequenced and the results were compared with the preset sequences on the BLAST program, 99% coinciding with R. rickettsii. The low sensitivity of the health system to recognize this disease and the insufficient information generated from tourism-related media are factors that affect the delay to implement effective treatment and appropriate prevention standards.

Introduction: Rickettsiosis caused by Rickettsia rickettsii is capable of infecting vertebrates, including humans. The symptoms are high fever, headache, myalgia, nausea, vomiting, abdominal pain, and cough. Mortality can be up to 30% in untreated patients., Aims: To prove the existence of rickettsiosis in Ensenada, Baja California, Mexico, because no human cases have been reported., Material and Methods: This observational, cross-sectional, descriptive study included 384 samples of humans in Ensenada, Baja California. Antibodies against R. rickettsii were measured with the kit R. rickettsii ELISA(®) Helica Biosystems, Inc., adapted for use in humans using human IgG conjugate antibodies. To determine the sensitivity and specificity, 32 human samples were submitted to IFA. Specific primers were used for the molecular diagnosis of R. rickettsii in dogs and ticks., Results: The seroprevalence adjusted rickettsiosis in humans was 2.9% (95% CI: 0.8-5.3), seropositivity was not associated with sex, age, occupation, household, dogs, pet deworming program against ticks, the type of yard, and mobility of the dog between home and the street., Conclusions: With substantial agreement of k between ELISA and IFA, it follows that the results of seroprevalence of this work are reliable.

Rickettsia rickettsii is the etiological agent of Rocky Mountain spotted fever (RMSF). YbgF and TolC are outer membrane-associated proteins of R. rickettsii that play important roles in its interaction with host cells. We investigated the immunogenicity of YbgF and TolC for protection against RMSF. We immunized C3H/HeN mice with recombinant R. rickettsii YbgF (rYbgF) or TolC (rTolC). Rickettsial burden and impairment in the lungs, spleens, and livers of rYbgF-immunized mice were significantly lower than in rTolC-immunized mice. The ratio of IgG2a to IgG1 in rYbgF-immunized mice continued to increase over the course of our experiments, while that in rTolC-immunized mice was reduced. The proliferation and cytokine secretion of CD4(+) and CD8(+) T cells isolated from R. rickettsii-infected mice were analyzed following antigen stimulation. The results indicated that proliferation and interferon (IFN)-γ secretion of CD4(+) or CD8(+) T cells in R. rickettsii-infected mice were significantly greater than in uninfected mice after stimulation with rYbgF. YbgF is a novel protective antigen of R. rickettsii. Protection conferred by YbgF is dependent upon IFN-γ-producing CD4(+) and CD8(+) T cells and IgG2a, which act in synergy to control R. rickettsii infection.

Introduction: Brazilian spotted fever (BSF) is a disease transmitted by ticks for which the etiological agent is Rickettsia rickettsii. The present essay evaluates the risk factors associated with the transmission of cases of BSF in the time period between 2003 and 2013 in the Piracicaba river basin, state of São Paulo., Methods: This essay presents a retrospective study to identify the factors associated with the transmission of cases of BSF among all suspected cases identified by the System for Epidemiological Surveillance of São Paulo (CVE). After the description of temporal distribution (onset of symptoms) and the environmental and demographic variations of the confirmed and discarded cases, a multiple logistic regression model was applied., Results: We searched 569 probable locations of infection (PLI) with 210 (37%) confirmed cases of BSF and 359 (63%) discarded cases. The associated variables for the confirmation of BSF in the multiple logistic model using a confidence interval (CI) of 95% were age (OR = 1.025 CI: 1.015-1.035), the presence of Amblyomma sculptum in the environment (OR = 1.629 CI: 1.097-2.439), the collection of ticks from horses (OR = 1.939 CI: 0.999-3.764), the presence of capybaras (OR = 1.467 CI: 1.009-2.138), an urban environment (OR = 1.515 CI: 1.036-2.231), and the existence of a dirty pasture (OR = 1.759 CI: 1.028-3.003)., Conclusions: The factors associated with the confirmation of BSF cases included an urban environment, age, presence of the A. sculptum vector, the collection of ticks from horses, the presence of a capybara population, and a dirty pasture environment.

Rocky Mountain spotted fever (RMSF) transmitted by the brown dog tick (Rhipicephalus sanguineus sensu lato) has emerged as a significant public health risk on American Indian reservations in eastern Arizona. During 2003-2012, more than 250 RMSF cases and 19 deaths were documented among Arizona's American Indian population. The high case fatality rate makes community-level interventions aimed at rapid and sustained reduction of ticks urgent. Beginning in 2012, a two year pilot integrated tick prevention campaign called the RMSF Rodeo was launched in a ∼ 600-home tribal community with high rates of RMSF. During year one, long-acting tick collars were placed on all dogs in the community, environmental acaricides were applied to yards monthly, and animal care practices such as spay and neuter and proper tethering procedures were encouraged. Tick levels, indicated by visible inspection of dogs, tick traps and homeowner reports were used to monitor tick presence and evaluate the efficacy of interventions throughout the project. By the end of year one, <1% of dogs in the RMSF Rodeo community had visible tick infestations five months after the project was started, compared to 64% of dogs in Non-Rodeo communities, and environmental tick levels were reduced below detectable levels. The second year of the project focused on use of the long-acting collar alone and achieved sustained tick control with fewer than 3% of dogs in the RMSF Rodeo community with visible tick infestations by the end of the second year. Homeowner reports of tick activity in the domestic and peridomestic setting showed similar decreases in tick activity compared to the non-project communities. Expansion of this successful project to other areas with Rhipicephalus-transmitted RMSF has the potential to reduce brown dog tick infestations and save human lives.

Fifteen bacterial isolates from spotted fever group rickettsiosis in Brazil were genetically identified as Rickettsia rickettsii. In a phylogenetic analysis with other R. rickettsii isolates from GenBank, the Central/South American isolates showed low polymorphism and formed a clade distinct from two North American clades, with the North American clades having greater in-branch polymorphism., (Copyright © 2014, American Society for Microbiology. All Rights Reserved.)

Among 13 suspected Rocky Mountain spotted fever (RMSF) cases identified through an enhanced surveillance program in Tennessee, antibodies to Rickettsia rickettsii were detected in 10 (77%) patients using a standard indirect immunofluorescent antibody (IFA) assay. Immunoglobulin M (IgM) antibodies were observed for 6 of 13 patients (46%) without a corresponding development of IgG, and for 3 of 10 patients (30%) at least 1 year post-onset. However, recent infection with a spotted fever group rickettsiae could not be confirmed for any patient, based on a lack of rising antibody titers in properly timed acute and convalescent serologic specimens, and negative findings by polymerase chain reaction testing. Case definitions used in national surveillance programs lack specificity and may capture cases that do not represent current rickettsial infections. Use of IgM antibodies should be reconsidered as a basis for diagnosis and public health reporting of RMSF and other spotted fever group rickettsiae in the United States., (© The American Society of Tropical Medicine and Hygiene.)

Rocky Mountain spotted fever is endemic to the São Paulo metropolitan area, Brazil, where the etiologic agent, Rickettsia rickettsii, is transmitted to humans by adult Amblyomma aureolatum ticks. We determined the minimal feeding period required by A. aureolatum nymphs and adults to transmit R. rickettsii to guinea pigs. Unfed nymphs and unfed adult ticks had to be attached to the host for >10 hours to transmit R. rickettsii. In contrast, fed ticks needed a minimum of 10 minutes of attachment to transmit R. rickettsii to hosts. Most confirmed infections of Rocky Mountain spotted fever in humans in the São Paulo metropolitan area have been associated with contact with domestic dogs, the main host of A. aureolatum adult ticks. The typical expectation that transmission of tickborne bacteria to humans as well as to dogs requires ≥2 hours of tick attachment may discourage persons from immediately removing them and result in transmission of this lethal bacterium.

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., (Published by Oxford University Press on behalf of the Infectious Diseases Society of America 2014. This work is written by (a) US Government employee(s) and is in the public domain in the US.)

Purpura fulminans (PF) is associated with several infections, most notably with meningococcus, staphylococcus, and streptococcus infections. However, there are few reports of association of this entity with spotted fever from India. We report the case of a 55-year-old man who presented with fever, headache, and myalgia. On the seventh day of fever he developed nonblanching purple hemorrhagic purpura on the trunk and most prominently on the extremities consistent with purpura fulminans. Immunofluorescent assay confirmed the diagnosis of spotted fever. PF though common with rocky mountain spotted fever (RMSF) is rarely seen in association with Indian tick typhus, the usual cause of spotted fever in India.