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Revista Do Instituto de Medicina... 2022Brazilian spotted fever, a zoonotic disease transmitted by ticks, is caused by Rickettsia rickettsii. We report a fulminant case of this zoonosis in a healthy...
Brazilian spotted fever, a zoonotic disease transmitted by ticks, is caused by Rickettsia rickettsii. We report a fulminant case of this zoonosis in a healthy 46-year-old military man in the urban region of Rio de Janeiro city, in October, 2021. Ticks and capybaras (Amblyomma sculptum, Hydrochoerus hydrochaeris, respectively) were identified in the military fields, pointing to the participation of this large synanthropic rodent, recognized as an efficient amplifier host of Rickettsia rickettsii in Brazil. As the military population is considered a risk group for spotted fever, it is necessary to alert health professionals to the importance of the early detection of the disease and its adequate management, mainly in populations that are particularly at risk of exposure to ticks, in order to avoid fatal outcomes.
Topics: Animals; Humans; Rocky Mountain Spotted Fever; Military Personnel; Brazil; Rickettsia rickettsii; Rodentia; Ticks
PubMed: 36383899
DOI: 10.1590/S1678-9946202264077 -
Vaccines Sep 2022Outbreaks of life-threatening Rocky Mountain spotted fever in humans and dogs associated with a canine-tick maintenance cycle constitute an important One Health... (Review)
Review
Outbreaks of life-threatening Rocky Mountain spotted fever in humans and dogs associated with a canine-tick maintenance cycle constitute an important One Health opportunity. The reality of the problem has been observed strikingly in Mexico, Brazil, Colombia, and Native American tribal lands in Arizona. The brown dog tick, , acquires the rickettsia from bacteremic dogs and can maintain the bacterium transtadially to the next tick stage. The subsequent adult tick can then transmit infection to a new host, as shown by guinea pig models. These brown dog ticks maintain spotted fever group rickettsiae transovarially through many generations, thus serving as both vector and reservoir. Vaccine containing whole-killed does not stimulate sufficient immunity. Studies of subunit antigens have demonstrated that conformationally preserved outer-membrane autotransporter proteins A and B are the leading vaccine candidates. The possibility of a potentially safe and effective live attenuated vaccine has only begun to be explored as gene knockout methods are applied to these obligately intracellular pathogens.
PubMed: 36298491
DOI: 10.3390/vaccines10101626 -
Pathogens (Basel, Switzerland) Sep 2022Acute febrile illness (AFI) is a morbid condition with a sudden onset of fever with at least seven days of evolution, where no signs or symptoms related to an apparent...
Acute febrile illness (AFI) is a morbid condition with a sudden onset of fever with at least seven days of evolution, where no signs or symptoms related to an apparent infection have been identified. In Latin America, a high proportion of disease is typically due to malaria and arboviruses. However, among the infectious etiologies, tick-borne diseases (TBDs) should also be considered, especially in areas where people come into direct contact with these arthropods. This study aims to describe the etiology and epidemiology related to tick-borne agents in patients with AFI and the tick's natural infection by agents of TBD in the rural tropical Magdalena Medio region in Colombia, and explore the factors associated with the presence of infection. We conduct a cohort study enrolling 271 patients with AFI to detect the bacteria of the genera , and through molecular techniques, and additionally evaluate the presence of IgG antibodies with commercially available kits. We also conduct tick collection in the patient's households or workplaces for the molecular screening of the same bacterial genera. Seropositivity to IgG antibodies was obtained for all the bacteria analyzed, with being the most common at 39.5% (107/271), followed by at 31.4% (85/271), at 26.9% (73/271), at 15.5% (42/271), at 14.4% (39/271), and at 6.6% (18/271). However, these bacteria were not detected by the molecular techniques used. infection was detected in 39.5% of the patients: 49.5% only by phase I and II IgG antibodies, 33.6% only by real-time PCR, and 16.8% had a concordant positive result for both techniques. A total of 191 adult ticks, 111 females and 80 males, were collected and identified as s.l. and . In the 169 adult ticks in which natural infection was evaluated, spp. was detected in 21.3% (36/169), spp. in 11.8% (20/169), and spp. in 4.7% (8/169). In conclusion, we identified the prior exposition to , and in patients through serological tests. We also detected the infection of using molecular techniques. In the ticks, we identified bacteria of the genera and . These results suggest the importance of these zoonotic agents as possible causes of AFI in this region.
PubMed: 36297148
DOI: 10.3390/pathogens11101090 -
PLoS Neglected Tropical Diseases Oct 2022Current isolation techniques for spotted fever group Rickettsia from clinical samples are laborious and are limited to tissue, blood and blood derivatives with volumes...
BACKGROUND
Current isolation techniques for spotted fever group Rickettsia from clinical samples are laborious and are limited to tissue, blood and blood derivatives with volumes ideally greater than 1 mL. We validated the use of simplified methodologies for spotted fever group Rickettsia culture isolation that overcome sample volume limitations and provide utility in clinical diagnostics and research studies.
METHODOLOGY/PRINCIPAL FINDINGS
A modified cell culture method is evaluated for the isolation of Rickettsia ssp. from human diagnostic samples. Culture sampling method, culture platform, and growth phase analysis were evaluated to determine best practices for optimal culture isolation conditions. Rickettsial isolates (R. conorii, R. rickettsii, and R. parkeri) were grown in Vero E6 cells over a course of 5 to 7 days at low inoculum treatments (~40 bacterial copies) to standardize the sampling strategy at a copy number reflective of the bacteremia in acute diagnostic samples. This methodology was verified using small volumes (50 μL) of 25 unprocessed clinical whole blood, plasma, and serum samples from acute samples of patients suspected of having Rocky Mountain Spotted Fever, of which 10 were previously confirmed positive via the PanR8 qPCR assay, 13 had no detectable Rickettsia DNA by the PanR8 qPCR assay, and 2 were not previously tested; these samples resulted in the cultivation of 7 new R. rickettsii isolates.
CONCLUSIONS/SIGNIFICANCE
We observed that rickettsial isolate growth in culture is reproducibly identified by real-time PCR testing of culture media within 72 hours after inoculation. Additionally, specimen sedimentation prior to isolation to remove red blood cells was found to decrease the amount of total organism available in the inoculum. A small volume culture method was established focusing on comparative qPCR detection rather than bacterial visualization, taking significantly shorter time to detect, and requiring less manipulation compared to traditional clinical isolate culture methods.
Topics: Humans; Rickettsia; Rocky Mountain Spotted Fever; Real-Time Polymerase Chain Reaction; Culture Media; Rickettsia rickettsii
PubMed: 36240222
DOI: 10.1371/journal.pntd.0010781 -
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 -
Ticks and Tick-borne Diseases Nov 2022The American dog tick, Dermacentor variabilis, is a major pest to humans and animals, serving as a vector to Rickettsia rickettsii, a bacterium responsible for Rocky...
The American dog tick, Dermacentor variabilis, is a major pest to humans and animals, serving as a vector to Rickettsia rickettsii, a bacterium responsible for Rocky Mountain spotted fever, and Francisella tularensis, which is responsible for tularemia. Although several tactics for management have been deployed, very little is known about the molecular response following pesticidal treatments in ticks. In this study, we used a combined approach utilizing transcriptomics and metabolomics to understand the response of the American dog tick to five common pesticides (amitraz, chlorpyrifos, fipronil, permethrin, and propoxur), and analyzed previous experimental data utilizing DEET repellent. Exposure to different chemicals led to significant differential expression of a varying number of transcripts, where 42 were downregulated and only one was upregulated across all treatments. A metabolomic analysis identified significant changes in acetate and aspartate levels following exposure to chlorpyrifos and propoxur, which was attributed to reduced cholinesterase activity. Integrating the metabolomics study with RNA-seq analysis, we found the physiological manifestations of the combined metabolic and transcriptional differences, revealing several novel biomolecular pathways. In particular, we discovered the downregulation of amino sugar metabolism and methylhistidine metabolism after permethrin exposure, as well as an upregulation of glutamate metabolism in amitraz treated samples. Understanding these altered biochemical pathways following pesticide and repellent exposure can help us formulate more effective chemical treatments to reduce the burden of ticks.
PubMed: 36099731
DOI: 10.1016/j.ttbdis.2022.102033 -
The American Journal of Tropical... Oct 2022Rocky Mountain spotted fever (RMSF) is a potentially fatal tickborne disease caused by the bacterium, Rickettsia rickettsii and transmitted primarily by the brown dog...
Rocky Mountain spotted fever (RMSF) is a potentially fatal tickborne disease caused by the bacterium, Rickettsia rickettsii and transmitted primarily by the brown dog tick (Rhipicephalus sanguineus) in the southwestern United States and Mexico. RMSF can be rapidly fatal if not treated early with doxycycline, making healthcare worker awareness and education critical to reduce morbidity and mortality. During 2008-2019, Mexicali experienced a RMSF epidemic with 779 confirmed cases, and an 11-year case-fatality rate of 18% (N = 140). A cross-sectional study was conducted with 290 physicians and physicians-in-training across 12 medical facilities in Mexicali. They were asked to complete a 23-item questionnaire to assess knowledge, attitudes, and practices for clinical, epidemiologic, and preventive aspects of RMSF. Half of participants were female, the largest age group was aged 25 to 44 (47%), and median time in practice was 6 years (interquartile rate: 1-21.5). Less than half (48%) surveyed were confident where diagnostic testing could be performed, and two-thirds did not regularly order serology (67%) or molecular diagnostic (66%) tests for RMSF when a patient presented with fever. Sixty-four percent knew doxycycline as first-line treatment of children < 8 years with suspected RMSF. When comparing healthcare workers with < 6 years of experience to those with ≥ 6 years, more experience was associated with greater confidence in where to have diagnostic testing performed (prevalence odds ratio [prevalence odds ratios [pOR]] = 2.3; P = 0.004), and frequency of ordering laboratory tests (serology, pOR = 3.3; P = 0.002; polymerase chain reaction, pOR = 3.9; P = 0.001). Continued education, including information on diagnostic testing is key to reducing morbidity and mortality from RMSF.
Topics: Animals; Cross-Sectional Studies; Dogs; Doxycycline; Female; Health Knowledge, Attitudes, Practice; Humans; Male; Mexico; Physicians; Rhipicephalus sanguineus; Rickettsia rickettsii; Rocky Mountain Spotted Fever
PubMed: 35995132
DOI: 10.4269/ajtmh.21-1017 -
Infection and Immunity Sep 2022Ticks are hematophagous ectoparasites capable of transmitting multiple human pathogens. Environmental changes have supported the expansion of ticks into new geographical... (Review)
Review
Ticks are hematophagous ectoparasites capable of transmitting multiple human pathogens. Environmental changes have supported the expansion of ticks into new geographical areas that have become the epicenters of tick-borne diseases (TBDs). The spotted fever group (SFG) of frequently infects ticks and causes tick-transmitted rickettsioses in areas of endemicity where ixodid ticks support host transmission during blood feeding. Ticks also serve as a reservoir for SFG . Among the members of SFG , R. rickettsii causes Rocky Mountain spotted fever (RMSF), the most lethal TBD in the United States. Cases of RMSF have been reported for over a century in association with several species of ticks in the United States. However, the isolation of R. rickettsii from ticks has decreased, and recent serological and epidemiological studies suggest that novel species of SFG are responsible for the increased number of cases of RMSF-like rickettsioses in the United States. Recent analyses of rickettsial genomes and advances in genetic and molecular studies of provided insights into the biology of with the identification of conserved and unique putative virulence genes involved in the rickettsial life cycle. Thus, understanding -host-tick interactions mediating successful disease transmission and pathogenesis for SFG rickettsiae remains an active area of research. This review summarizes recent advances in understanding how SFG species coopt and manipulate ticks and mammalian hosts to cause rickettsioses, with a particular emphasis on newly described or emerging SFG species.
Topics: Animals; Humans; Ixodidae; Mammals; Rickettsia; Rickettsia Infections; Rocky Mountain Spotted Fever; Ticks
PubMed: 35993770
DOI: 10.1128/iai.00621-21 -
EJHaem May 2022A three-year-old boy presented with fever, maculopapular rash involving palms and soles, and hyponatremia two weeks following a tick bite. Empiric doxycycline that he...
A three-year-old boy presented with fever, maculopapular rash involving palms and soles, and hyponatremia two weeks following a tick bite. Empiric doxycycline that he was on was discontinued following negative initial rickettsial serology based on the non-endemicity of Rocky Mountain spotted fever (RMSF) in Northeast Ohio. He demonstrated high inflammatory markers and met the criteria for hemophagocytic lymphohistiocytosis (HLH). With a working diagnosis of macrophage activation syndrome secondary to presumed systemic-onset juvenile idiopathic arthritis (soJIA), he received HLH-directed therapy. Rising antibody titers in convalescent sera established the diagnosis of RMSF. The patient recovered completely with HLH directed therapy and re-institution of doxycycline. This is the first pediatric case report of induced HLH demonstrating a favorable outcome despite modified therapy.
PubMed: 35846066
DOI: 10.1002/jha2.405 -
The American Journal of Case Reports Jul 2022BACKGROUND Babesia species are intraerythrocytic parasitic protozoa that are endemic to the Northeast and north Midwest of the United States. Babesia microti is the most...
BACKGROUND Babesia species are intraerythrocytic parasitic protozoa that are endemic to the Northeast and north Midwest of the United States. Babesia microti is the most common cause of babesiosis in North America and causes a malaria-like tick-borne parasitosis. Babesia is commonly transmitted through the bite of Ixodes species ticks, often concomitantly with other tick-borne organisms such as Borrelia burgdorferi, Ehrlichia, Rickettsia rickettsii, and Anaplasma phagocytophilum. In the Midwest, Lyme disease is the most common tick-borne illness, and other organisms can sometimes be overlooked. The risk of tick-borne parasitic or bacterial infection is increased in patients after splenectomy. CASE REPORT An 89-year-old man with asplenia and multiple other comorbidities presented to the Emergency Department after a fall at home preceded by 2 to 3 days of fever and loss of appetite and 1 week of generalized weakness. The patient had thrombocytopenia, leukocytosis with neutrophilia, transaminitis, hyperbilirubinemia, and elevated creatine kinase level consistent with tick-borne illness. Laboratory testing revealed Borrelia and Babesia co-infection and other culprits were ruled out via high sensitivity PCR. Owing to the patient's asplenic status, the babesiosis was slow to resolve with appropriate treatment. After an extended 8-week treatment with azithromycin and atovaquone, the patient demonstrated clinical resolution of babesiosis with a negative blood smear. CONCLUSIONS First-line treatment with azithromycin and atovaquone is effective in treating babesiosis even in complicated patients, such as this elderly, asplenic patient. However, in cases such as this, an extended course of a first-line treatment regimen is still appropriate.
Topics: Aged; Aged, 80 and over; Atovaquone; Azithromycin; Babesia; Babesiosis; Humans; Male; Parasitemia; Trust; United States
PubMed: 35844076
DOI: 10.12659/AJCR.936326