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Ticks and Tick-borne Diseases Jul 2020Dermacentor andersoni, the Rocky Mountain wood tick, occurs predominantly in the northwestern United States and southwestern Canada. There are relatively few...
Dermacentor andersoni, the Rocky Mountain wood tick, occurs predominantly in the northwestern United States and southwestern Canada. There are relatively few contemporary data to evaluate the occurrence of Rickettsia and Anaplasma species in D. andersoni in western North America, and even less information about these associations in the state of Washington, where this tick species is widely distributed and often bites humans. We used PCR assays to detect DNA of Rickettsia and Anaplasmataceae bacteria in 203 adult D. andersoni ticks collected from 17 sites in 9 counties of Washington between May 2012 and May 2015. Of these, 56 (27.6 %) were infected with a Rickettsia species and 3 (5.4 %) with a member of the Anaplasmataceae family. Rickettsia peacockii, R. bellii and R. rhipicephali were found in 17.7 %, 4.9 %, and 4.4 % of the Rickettsia positive ticks, respectively. Coinfections of R. bellii with R. peacockii or R. rhipicephali were identified in 6 ticks. Of the Anaplasmataceae-positive ticks, one was identified as being infected with Anaplasma phagocytophilum AP-Variant 1. No ticks were infected with a recognized human or animal pathogen, including R. rickettsii, A. phagocytophilum-ha, A. bovis, or A. marginale.
Topics: Anaplasma; Animals; Dermacentor; Female; Male; Rickettsia; Washington
PubMed: 32273163
DOI: 10.1016/j.ttbdis.2020.101422 -
Scientific Reports Mar 2023Rocky Mountain spotted fever (RMSF) is a rapidly progressive and often fatal tick-borne disease caused by Rickettsia rickettsii. Its discovery and characterization by...
Rocky Mountain spotted fever (RMSF) is a rapidly progressive and often fatal tick-borne disease caused by Rickettsia rickettsii. Its discovery and characterization by Howard Ricketts has been hailed as a remarkable historical example of detection and control of an emerging infectious disease, and subsequently led to the establishment of the Rocky Mountain Laboratories (RML). Here, we examined an unopened bottle of a vaccine, labeled as containing RMSF inactivated by phenol-formalin of infected ticks, developed prior to 1944 at RML by DNA analysis using Illumina high throughput sequencing technology. We found that it contains DNA from the Rocky Mountain wood tick (Dermacentor andersoni), the vector of RMSF, the complete genome of Rickettsia rickettsii, the pathogen of RMSF, as well as the complete genome of Coxiella burnetii, the pathogen of Q-fever. In addition to genomic reads of Rickettsia rickettsii and Coxiella burnetii, smaller percentages of the reads are from Rickettsia rhipicephali and Arsenophonus nasoniae, suggesting that the infected ticks used to prepare the vaccine carried more than one pathogen. Together, these findings suggest that this early vaccine was likely a bivalent vaccine for RMSF and Q-fever. This study is the among the first molecular level examinations of an historically important vaccine.
Topics: Animals; Rocky Mountain Spotted Fever; Rickettsia rickettsii; Ticks; Coxiella burnetii; Vaccines
PubMed: 36949107
DOI: 10.1038/s41598-023-31894-0 -
Infection and Immunity Mar 2021, the etiological agent of Rocky Mountain spotted fever (RMSF), a life-threatening tick-borne disease that affects humans and various animal species, has been recognized...
, the etiological agent of Rocky Mountain spotted fever (RMSF), a life-threatening tick-borne disease that affects humans and various animal species, has been recognized in medicine and science for more than 100 years. Isolate-dependent differences in virulence of have been documented for many decades; nonetheless, the specific genetic and phenotypic factors responsible for these differences have not been characterized. Using and methods, we identified multiple phenotypic differences among six geographically distinct isolates of , representing isolates from the United States, Costa Rica, and Brazil. Aggregate phenotypic data, derived from growth in Vero E6 cells and from clinical and pathological characteristics following infection of male guinea pigs (), allowed separation of these isolates into three categories: nonvirulent (Iowa), mildly virulent (Sawtooth and Gila), and highly virulent (Sheila Smith, Costa Rica, and Taiaçu). Transcriptional profiles of 11 recognized or putative virulence factors confirmed the isolate-dependent differences between mildly and highly virulent isolates. These data corroborate previous qualitative assessments of strain virulence and suggest further that a critical and previously underappreciated balance between bacterial growth and host immune response could leverage strain pathogenicity. Also, this work provides insight into isolate-specific microbiological factors that contribute to the outcome of RMSF and confirms the hypothesis that distinct rickettsial isolates also differ phenotypically, which could influence the severity of disease in vertebrate hosts.
Topics: Animals; Bacterial Load; Biomarkers; Disease Models, Animal; Disease Susceptibility; Gene Expression Regulation, Bacterial; Guinea Pigs; Host-Pathogen Interactions; Humans; Immunohistochemistry; Male; Rickettsia rickettsii; Rocky Mountain Spotted Fever; Symptom Assessment; Virulence; Virulence Factors
PubMed: 33495273
DOI: 10.1128/IAI.00626-20 -
Ticks and Tick-borne Diseases Mar 2023Two well characterized tick-borne rickettsioses occur in Brazil. Rickettsia rickettsii caused spotted-fever, transmitted by Amblyomma sculptum and Amblyomma aureolatum,... (Review)
Review
Two well characterized tick-borne rickettsioses occur in Brazil. Rickettsia rickettsii caused spotted-fever, transmitted by Amblyomma sculptum and Amblyomma aureolatum, is a severe disease with a high case-fatality rate in the southeastern region of the country. Rickettsia parkeri strain Atlantic rainforest infections transmitted by adult Amblyomma ovale ticks cause a milder non-lethal febrile disease with an eschar (necrosis) at the tick bite site. Clinical diagnosis of rickettsiosis is challenging, particularly during the early stages of the illness when signs and symptoms are non-specific. Since eschar at the tick bite site has emerged as the main clinical feature of mild R. parkeri infections and used to differentiate it from severe R. rickettsii infection, its proper recognition, distinction from other tick bite lesions, and boundaries as a clinical tool must be highlighted. Of importance, eschars induced by Rickettsia must be differentiated from dermatoses caused by other tick-borne skin infections as well from lesions caused by the tick bite itself. We herein highlight information on eschar in rickettsial diseases in Brazil and discuss the need for further research on its clinical relevance and application in the diagnosis of spotted fever caused by R. parkeri strain Atlantic rainforest. In particular, we draw attention to diagnosis of other febrile diseases in the presence of concomitant tick bites.
Topics: Animals; Adult; Humans; Tick Bites; Brazil; Ixodidae; Rickettsia; Rickettsia Infections; Spotted Fever Group Rickettsiosis; Amblyomma; Tick-Borne Diseases; Skin Diseases
PubMed: 36693294
DOI: 10.1016/j.ttbdis.2023.102127 -
The American Journal of Tropical... Mar 2022Clinical and laboratory diagnosis of rickettsial diseases is challenging because of the undifferentiated symptoms (commonly fever, headache, and malaise) and low...
Clinical and laboratory diagnosis of rickettsial diseases is challenging because of the undifferentiated symptoms (commonly fever, headache, and malaise) and low bacteremia (< 100 genomic copies [gc]/mL) during the early acute stage of illness. Early treatment with doxycycline is critical for a positive outcome, especially in Rickettsia rickettsii (Rocky Mountain spotted fever) infections where cases may be fatal within 5 to 10 days from symptom onset, emphasizing the need for more sensitive diagnostics. A real-time reverse transcriptase polymerase chain reaction (PCR) assay, RCKr, was developed and validated for Rickettsia spp. nucleic acid detection in human clinical samples. The limit of detection for RCKr was determined to be 20 gc/mL, compared with our 2013 (Kato et al.) laboratory developed test, PanR8 at 1,800 to 2,000 gc/mL. Inclusivity, exclusivity, accuracy, and precision results correlated as expected. From an evaluation of 49 banked clinical samples, RCKr detected 35 previously positive samples, as well as two specimens that were PanR8 real-time PCR negative yet clinically diagnosed as possible rickettsiosis. Ct values from RCKr clinical sample testing show a 100-fold increase relative to PanR8. Additional testing is needed to understand the clinical sensitivity of RCKr; however, this study demonstrates RCKr to have high analytical specificity and sensitivity for Rickettsia detection.
PubMed: 35292596
DOI: 10.4269/ajtmh.21-0757 -
Vector Borne and Zoonotic Diseases... Dec 2022Spotted fever rickettsiosis is caused by a group of closely related bacteria that includes , the etiological agent of Rocky Mountain spotted fever. Recently, has been...
Spotted fever rickettsiosis is caused by a group of closely related bacteria that includes , the etiological agent of Rocky Mountain spotted fever. Recently, has been reported to cause clinical and subclinical symptoms in both humans and animal models. In this study, we collected ticks in Ashland County, located in northern Wisconsin, and tested 16 ticks identified as for the presence of rickettsial bacteria using PCR techniques. Four positive results identified using gel electrophoresis were then sequenced to determine the rickettsiae species. Of the samples sequenced, three matched for (∼19% of the 16 ticks tested). In this study, we report the presence and prevalence of in northern Wisconsin.
Topics: Animals; Humans; Dermacentor; Rickettsia; Rocky Mountain Spotted Fever; Wisconsin
PubMed: 36322883
DOI: 10.1089/vbz.2022.0055 -
Vector Borne and Zoonotic Diseases... Apr 2021Members of the genus range from nonpathogenic endosymbionts to virulent pathogens such as , the causative agent of Rocky Mountain spotted fever. Many rickettsiae are...
Members of the genus range from nonpathogenic endosymbionts to virulent pathogens such as , the causative agent of Rocky Mountain spotted fever. Many rickettsiae are considered nonpathogenic because they have been isolated from ticks but not vertebrate hosts. We assessed the ability of three presumed endosymbionts: , , and , to infect a guinea pig animal model. These species were chosen because of their high prevalence in respective tick vectors or published reports suggestive of human or animal pathogenicity. Following intraperitoneal (IP) inoculation of cell culture suspensions of , , , or into guinea pigs, animals were monitored for signs of clinical illness for 13 days. Ear biopsies and blood samples were taken at 2- to 3-day intervals for detection of rickettsial DNA by PCR. Animals were necropsied and internal organ samples were also tested using PCR assays. Among the six guinea pigs inoculated with , fever, orchitis, and dermatitis were observed in one, one, and three animals respectively. In -exposed animals, we noted fever in one of six animals, orchitis in one, and dermatitis in two. No PCR-positive tissues were present in either the or exposed groups. In the -exposed group, two of six animals became febrile, two had orchitis, and three developed dermatitis in ears or footpads. DNA was detected in ear skin biopsies collected on multiple days from three animals. Also, a liver specimen from one animal and spleen specimens of two animals were PCR positive. The course and severity of disease in the three experimental groups were significantly milder than that of . This study suggests that the three rickettsiae considered nonpathogenic can cause either subclinical or mild infections in guinea pigs when introduced via IP inoculation.
Topics: Animals; Guinea Pigs; Male; Rickettsia; Ticks; Virulence
PubMed: 33600263
DOI: 10.1089/vbz.2020.2695 -
Revista Brasileira de Parasitologia... 2022The bacterium Rickettsia rickettsii is the etiological agent of Brazilian spotted fever (BSF), and its most important vector to humans in Brazil is the tick Amblyomma...
The bacterium Rickettsia rickettsii is the etiological agent of Brazilian spotted fever (BSF), and its most important vector to humans in Brazil is the tick Amblyomma sculptum. Capybaras are the main hosts of A. sculptum in many BSF-endemic areas and are considered valuable sentinels for BSF surveillance. This study aimed to assess the persistence of anti-R. rickettsii antibodies for long periods in capybaras and their passive transfer to offspring. For this purpose, three adult capybaras previously exposed to multiple infections with R. rickettsii were followed up until 3.1 years after their last exposure. During the study, one female delivered five cubs, of which three survived. Blood samples were collected monthly from adults and infants, and serum samples were titrated by indirect immunofluorescence assay (IFA) to determine endpoint titers of anti-R. rickettsii antibodies. All three adults remained seroreactive to R. rickettsii with high endpoint titers until the end of the study. All infants were seroreactive to R. rickettsii after birth and remained seroreactive for one to four months. This study showed that exposure of capybaras to R. rickettsii-infected A. sculptum ticks elicits a persistent antibody response. In addition, there was evidence of passive transfer of R. rickettsii-reactive antibodies to offspring.
Topics: Animals; Antigens, Bacterial; Brazil; Female; Humans; Ixodidae; Rickettsia rickettsii; Rocky Mountain Spotted Fever; Rodent Diseases; Rodentia; Ticks
PubMed: 36169507
DOI: 10.1590/S1984-29612022052 -
Vector Borne and Zoonotic Diseases... Dec 2021In the United States, and are considered key vectors for , the causative agent of Rocky Mountain spotted fever. Through regional surveillance, a wide diversity of...
In the United States, and are considered key vectors for , the causative agent of Rocky Mountain spotted fever. Through regional surveillance, a wide diversity of spp. have been documented in , and spp. has been suggested as potential vectors for various other pathogens, including spp. and . To better define the prevalence and diversity of pathogens in spp. across the United States, 848 ticks collected from dogs and cats in 44/50 states in 2018-2019 were tested by PCR for spp.-specific 17 kDa and ompA gene fragments; a subset of spp. was also tested with PCR, targeting fragments of the 18S and large subunit region rRNA genes of spp. and 16S rRNA genes of . spp. was identified in 12.5% (106/848) of ticks. Species detected include ( = 64 ticks), ( = 15 ticks), ( = 13 ticks), ( = 8 ticks), ( = 3 ticks), ( = 1 tick), and unclassified spp. ( = 2 ticks). Ticks with and were submitted from every U.S. region; was predominantly detected in ticks from the southern half of the United States, and all -positive ticks were that originated from the Rocky Mountain states. was not detected in any spp., and was detected in two . Because most ticks had fed on dogs or cats before submission, these findings do not implicate a given sp. as a primary vector of these agents, but in regard to spp., the data do support other published work showing harbors a diversity of species with unknown implications for animal and human health.
Topics: Animals; Babesia; Cat Diseases; Cats; Dermacentor; Dog Diseases; Dogs; RNA, Ribosomal, 16S; Rickettsia; United States
PubMed: 34958266
DOI: 10.1089/vbz.2021.0047 -
Current Research in Parasitology &... 2022Ticks are blood-sucking arthropods that parasitize most groups of terrestrial or semiaquatic vertebrates. Humans are accidental hosts to the ticks; however, in humans... (Review)
Review
Ticks are blood-sucking arthropods that parasitize most groups of terrestrial or semiaquatic vertebrates. Humans are accidental hosts to the ticks; however, in humans the ticks can cause damages varying from simple irritation to severe allergies, toxicosis, paralysis, and the transmission of pathogens, some of which can be fatal. Central America represents a narrow isthmus between North and South America and is considered a biodiversity hotspot. The importance of tick-borne diseases in this region is manifested by fatal outbreaks caused by , severe and mild cases of other rickettsioses, ehrlichiosis, and tick-borne relapsing fevers, in addition to cases paralysis and strong allergic reactions. Even so, this information is scarce in most countries of this region, and there are no epidemiological data. In this article we present a review of the ticks that parasitize humans in Central America, covering data from the 19th Century to the present day. Of nearly 80 tick species reported in Central America, 28 species are reported on humans. This list includes species that thrive within homes, grazing areas and, to a lesser extent, in wild environments, both in lowland and high mountain forests. The most important genus in this region is , followed by and , and to a lesser extent , and . These data provide information on the tick species most commonly associated with humans in Central America, and highlight the potential for tick-borne diseases in wild, rural and urban regions.
PubMed: 36589874
DOI: 10.1016/j.crpvbd.2021.100065