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Microorganisms Jun 2020Ticks are obligate hematophagous arthropods and act as vectors for a great variety of pathogens, including viruses, bacteria, protozoa, and helminths. Some tick-borne... (Review)
Review
Ticks are obligate hematophagous arthropods and act as vectors for a great variety of pathogens, including viruses, bacteria, protozoa, and helminths. Some tick-borne viruses, such as Powassan virus and tick-borne encephalitis virus, are transmissible within 15-60 min after tick attachment. However, a minimum of 3-24 h of tick attachment is necessary to effectively transmit bacterial agents such as spp., spp., and spp. to a new host. Longer transmission periods were reported for spp. and protozoans such as spp., which require a minimum duration of 24-48 h of tick attachment for maturation and migration of the pathogen. Laboratory observations indicate that the probability of transmission of tick-borne pathogens increases with the duration an infected tick is allowed to remain attached to the host. However, the transmission time may be shortened when partially fed infected ticks detach from their initial host and reattach to a new host, on which they complete their engorgement. For example, early transmission of tick-borne pathogens (e.g., , , and ) and a significantly shorter transmission time were demonstrated in laboratory experiments by interrupted blood feeding. The relevance of such situations under field conditions remains poorly documented. In this review, we explore parameters of, and causes leading to, spontaneous interrupted feeding in nature, as well as the effects of this behavior on the minimum time required for transmission of tick-borne pathogens.
PubMed: 32560202
DOI: 10.3390/microorganisms8060910 -
Rocky Mountain Spotted Fever in a Large Metropolitan Center, Mexico-United States Border, 2009-2019.Emerging Infectious Diseases Jun 2021Epidemic levels of Rocky Mountain spotted fever (RMSF) have persisted in Mexicali, Mexico, since the initial outbreak was first reported in December 2008. We... (Review)
Review
Epidemic levels of Rocky Mountain spotted fever (RMSF) have persisted in Mexicali, Mexico, since the initial outbreak was first reported in December 2008. We compared clinical and epidemiologic data of cases in Mexicali during 2009–2019 between patients with an IgG titer reactive with bacteria by indirect immunofluorescence antibody (IFA) assay and those who demonstrated DNA of in a whole blood sample when tested by PCR. We identified 4,290 patients with clinical and epidemiologic features compatible with RMSF; of these, 9.74% tested positive by IFA and 8.41% by PCR. Overall, 140 patients died (11-year case-fatality rate 17.97%). Substantial differences in the frequency of commonly recognized clinical characteristics of RMSF were identified between PCR-positive and IFA-positive cases. The Mexicali epidemic is unique in its size and urban centralization. Cases confirmed by PCR most accurately reflect the clinical profile of RMSF.
Topics: Animals; Mexico; Rhipicephalus sanguineus; Rickettsia rickettsii; Rocky Mountain Spotted Fever; United States
PubMed: 34014151
DOI: 10.3201/eid2706.191662 -
Clinical Infectious Diseases : An... Sep 2014Rickettsia rickettsii, Rickettsia parkeri, and Rickettsia akari are the most common causes of spotted fever group rickettsioses indigenous to the United States. Infected...
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.
Topics: Biopsy; Citrate (si)-Synthase; Exanthema; Humans; Real-Time Polymerase Chain Reaction; Rickettsia; Rickettsia Infections; Rickettsia akari; Rickettsia rickettsii; Rocky Mountain Spotted Fever; Sensitivity and Specificity; Skin
PubMed: 24829214
DOI: 10.1093/cid/ciu358 -
Dermatologic Therapy Jul 2021Cutaneous involvement can be an important sign of both COVID-19 and rickettsioses. Rickettsial infections may be first evident as an exanthem with eschars as a key... (Review)
Review
Cutaneous involvement can be an important sign of both COVID-19 and rickettsioses. Rickettsial infections may be first evident as an exanthem with eschars as a key finding. In contrast, eschars and necrotic lesions can be seen in critically ill COVID-19 patients. Both illnesses share a similar mechanism of infecting endothelial cells resulting in vasculopathy. Rickettsia parkeri and Rickettsia 364D are both characterized by eschars unlike Rickettsia rickettsii. Other eschar causing rickettsioses such as Rickettsia conorii, Rickettsia africae, and Orientia tsutsugamushi are commonly diagnosed in people from or having traveled through endemic areas. While there is no consensus on treatment for COVID-19, rickettsioses are treatable. Due to possibly serious consequences of delayed treatment, doxycycline should be administered given an eschar-presenting patient's travel history and sufficient suspicion of vector exposure. The proliferation of COVID-19 cases has rendered it critical to differentiate between the two, both of which may have overlapping vasculopathic cutaneous findings. We review these diseases, emphasizing the importance of cutaneous involvement, while also discussing possible therapeutic interventions.
Topics: COVID-19; Endothelial Cells; Humans; Rickettsia; Rickettsia Infections; SARS-CoV-2
PubMed: 34003557
DOI: 10.1111/dth.14984 -
MBio Apr 2024We compared the growth characteristics of a virulent strain (Sheila Smith) to an attenuated stain (Iowa) and a non-pathogenic species () in primary human dermal...
We compared the growth characteristics of a virulent strain (Sheila Smith) to an attenuated stain (Iowa) and a non-pathogenic species () in primary human dermal microvascular endothelial cells (HDMEC). All replicated in Vero cells, however, only the Sheila Smith strain productively replicated in HDMECs. The Iowa strain showed minimal replication over a 24-h period, while lost viability and induced lysis of the HDMECs via a rapid programmed cell death response. Both the virulent and attenuated strains, but not , induced an interferon-1 response, although the response was of lesser magnitude and delayed in the Sheila Smith strain. IFN-β secretion correlated with increased host cell lysis, and treatment with anti-IFNAR2 antibody decreased lysis from Iowa-infected but not Sheila Smith-infected cells. Both Sheila Smith- and Iowa-infected cells eventually lysed, although the response from Sheila Smith was delayed and showed characteristics of apoptosis. We, therefore, examined whether reconstitution of the Iowa strain with two recently described putative virulence determinants might enhance survival of Iowa within HDMECs. Reconstitution with RARP2, which is inhibitory to anterograde trafficking through the Golgi apparatus, reduced IFN-β secretion but had no effect on cell lysis. RapL, which proteolytically processes surface exposed autotransporters and enhances replication of Iowa in Guinea pigs, suppressed both IFN-β production and host cell lysis. These findings suggest distinct mechanisms by which virulent spotted fever group rickettsiae may enhance intracellular survival and replication.IMPORTANCEWe examined a naturally occurring non-pathogenic rickettsial species, , a laboratory-attenuated strain (Iowa), and a fully virulent strain (Sheila Smith) for growth in human dermal microvascular endothelial cells. The two avirulent strains replicated poorly or not at all. Only the virulent Sheila Smith strain replicated. IFN-β production correlated with the inhibition of Iowa. Reconstitution of Iowa with either of two recently described putative virulence determinants altered the IFN-β response. A rickettsial ankyrin repeat protein, RARP2, disrupts the Golgi network and inhibits IFN-β secretion. An autotransporter peptidase, RapL, restores proteolytic maturation of outer membrane autotransporters and diminishes the IFN-β response to enhance cell survival and permit replication of the recombinant strain. These studies point the way toward discovery of mechanisms for innate immune response avoidance by virulent rickettsia.
Topics: Animals; Guinea Pigs; Humans; Chlorocebus aethiops; Endothelial Cells; Rickettsia; Rickettsia rickettsii; Rocky Mountain Spotted Fever; Type V Secretion Systems; Vero Cells; Virulence; Virulence Factors; Interferon-beta
PubMed: 38445878
DOI: 10.1128/mbio.03450-23 -
Journal of Medical Entomology Jan 2016Rocky Mountain spotted fever, caused by Rickettsia rickettsii, is a potentially fatal tick-borne disease spread from North America to Argentina. The major vectors of R....
Effect of Rickettsia rickettsii (Rickettsiales: Rickettsiaceae) Infection on the Biological Parameters and Survival of Its Tick Vector-Dermacentor variabilis (Acari: Ixodidae).
Rocky Mountain spotted fever, caused by Rickettsia rickettsii, is a potentially fatal tick-borne disease spread from North America to Argentina. The major vectors of R. rickettsii in the United States are Dermacentor andersoni Stiles and Dermacentor variabilis (Say). It is generally believed that vector ticks serve as major reservoirs of R. rickettsii in nature; however, the ability of ticks to support the indefinite perpetuation of R. rickettsii has been challenged by reports of deleterious effects of rickettsial infection on D. andersoni. To better elucidate the relationship of the pathogen with D. variabilis, we assessed the effects of R. rickettsii on the survival, fertility, and fecundity of D. variabilis. We used an isolate of R. rickettsii (Di-6), originally acquired from an opossum caught in Virginia, and ticks from a laboratory colony established from adult D. variabilis also collected in Virginia. Overall, infection with R. rickettsii protracted the feeding periods of all life stages of ticks. Infected nymphal and adult ticks experienced a slight decrease in feeding success compared with the uninfected colony, but neither larval nor nymphal molting success was affected. Infected females reached smaller engorgement weights, were less efficient in conversion of bloodmeal into eggs, and produced smaller egg clutches with a lower proportion of eggs hatching. However, no sudden die-off was observed among infected ticks, and longevity was not decreased due to R. rickettsii infection in any stage. Although infection with the studied isolate of R. rickettsii caused slight decrease in fecundity in sympatric vector ticks, no obvious deleterious effects were observed.
Topics: Animals; Arthropod Vectors; Dermacentor; Feeding Behavior; Female; Host-Pathogen Interactions; Longevity; Molting; Rabbits; Rickettsia rickettsii; Rocky Mountain Spotted Fever
PubMed: 26494822
DOI: 10.1093/jme/tjv166 -
Infection and Immunity Aug 2000Actin-based motility (ABM) is a mechanism for intercellular spread that is utilized by vaccinia virus and the invasive bacteria within the genera Rickettsia, Listeria,...
Actin-based motility (ABM) is a mechanism for intercellular spread that is utilized by vaccinia virus and the invasive bacteria within the genera Rickettsia, Listeria, and Shigella. Within the Rickettsia, ABM is confined to members of the spotted fever group (SFG), such as Rickettsia rickettsii, the agent of Rocky Mountain spotted fever. Infection by each agent induces the polymerization of host cell actin to form the typical F (filamentous)-actin comet tail. Assembly of the actin tail propels the pathogen through the host cytosol and into cell membrane protrusions that can be engulfed by neighboring cells, initiating a new infectious cycle. Little is known about the structure and morphogenesis of the Rickettsia rickettsii actin tail relative to Shigella and Listeria actin tails. In this study we examined the ultrastructure of the rickettsial actin tail by confocal, scanning electron, and transmission electron microscopy. Confocal microscopy of rhodamine phalloidin-stained infected Vero cells revealed the typhus group rickettsiae, Rickettsia prowazekii and Rickettsia typhi, to have no actin tails and short (approximately 1- to 3-micrometer) straight or hooked actin tails, respectively. The SFG rickettsia, R. rickettsii, displayed long actin tails (>10 micrometer) that were frequently comprised of multiple, distinct actin bundles, wrapping around each other in a helical fashion. Transmission electron microscopy, in conjunction with myosin S1 subfragment decoration, revealed that the individual actin filaments of R. rickettsii tails are >1 micrometer long, arranged roughly parallel to one another, and oriented with the fast-growing barbed end towards the rickettsial pole. Scanning electron microscopy of intracellular rickettsiae demonstrated R. rickettsii to have polar associations of cytoskeletal material and R. prowazekii to be devoid of cytoskeletal interactions. By indirect immunofluorescence, both R. rickettsii and Listeria monocytogenes actin tails were shown to contain the cytoskeletal proteins vasodilator-stimulated phosphoprotein profilin, vinculin, and filamin. However, rickettsial tails lacked ezrin, paxillin, and tropomyosin, proteins that were associated with actin tails of cytosolic or protrusion-bound Listeria. The unique ultrastructural and compositional characteristics of the R. rickettsii actin tail suggest that rickettsial ABM is mechanistically different from previously described microbial ABM systems.
Topics: Actins; Animals; Chlorocebus aethiops; Cytoskeletal Proteins; Fluorescent Antibody Technique, Indirect; Microscopy, Confocal; Microscopy, Electron; Rickettsia rickettsii; Vero Cells
PubMed: 10899876
DOI: 10.1128/IAI.68.8.4706-4713.2000 -
Infection and Immunity Nov 1984Five mouse ascitic fluids (MAFs) containing monoclonal antibody to Rickettsia rickettsii were produced from three original fusions by murine hybridoma technology. The... (Comparative Study)
Comparative Study
Five mouse ascitic fluids (MAFs) containing monoclonal antibody to Rickettsia rickettsii were produced from three original fusions by murine hybridoma technology. The five MAFs were fractionated and purified; each contained monoclonal antibody of the immunoglobulin G2a subclass. Each monoclonal antibody-containing MAF was titrated by indirect immunofluorescence against three R. rickettsii isolates from humans and four other spotted fever group rickettsiae. Each MAF was also titrated in the complement fixation, latex agglutination, microagglutination, and indirect hemagglutination tests. Two of the MAFs were examined for their ability to prevent fever and rickettsemia in susceptible guinea pigs after a 1:100 dilution of each was mixed with viable R. rickettsii, and all five MAFs were titrated in the mouse toxicity phenomenon assay. All MAFs had high indirect immunofluorescence titers to the three strains of R. rickettsii (1:200,000 to 1:800,000), reduced indirect immunofluorescence titers to R. montana, and were nonreactive with R. akari, R. sibirica, and R. conorii. Each MAF was able to fix complement in the presence of spotted fever group antigen reagent and agglutinate a suspension of purified R. rickettsii, and each was negative in both the latex agglutination and the indirect hemagglutination tests. The two MAFs which were tested proved to be capable of preventing rickettsemia and death in guinea pigs, and each MAF was able to prevent death in mice at dilutions ranging from 1:40 to 1:80.
Topics: Animals; Antibodies, Monoclonal; Antibody Specificity; Complement Fixation Tests; Epitopes; Immunization, Passive; Immunoglobulin G; Mice; Rickettsia; Rickettsia rickettsii; Rocky Mountain Spotted Fever
PubMed: 6209219
DOI: 10.1128/iai.46.2.289-294.1984 -
The Korean Journal of Parasitology Oct 2021Ticks can transmit pathogenic bacteria, protozoa, and viruses to humans and animals. In this study, we investigated the microbiomes of Haemaphysalis longicornis...
Ticks can transmit pathogenic bacteria, protozoa, and viruses to humans and animals. In this study, we investigated the microbiomes of Haemaphysalis longicornis according to sex and life stages. The Shannon index was significantly higher for nymphs than adult ticks. Principal coordinates analysis showed that the microbiome composition of female adult and male adult ticks were different. Notably, Coxiella-like bacterium (AB001519), known as a tick symbiont, was found in all nymphs and female adult ticks, but only one out of 4 male adult ticks had Coxiella-like bacterium (AB001519). In addition, Rickettsia rickettsii, Coxiella burnetii, and Anaplasma bovis were detected in this study.
Topics: Anaplasma; Animals; Female; Humans; Ixodidae; Male; Microbiota; Republic of Korea; Rickettsia; Ticks
PubMed: 34724768
DOI: 10.3347/kjp.2021.59.5.489