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At least 19 recordsLinked to original sources
PubMed2002

Colorado tick fever.

Colorado tick fever, also known as mountain fever and mountain tick fever, is a well-described, viral, tick-borne disease common to the Rocky Mountain region of the United States and Canada. The Rocky Mountain wood tick, Dermacentor andersoni, is the primary vector. The triad of high fever, severe myalgia, and headache is typical, but not specific. Although a self-limited disease in most cases, severe complications may occur. PCR techniques have been developed that allow the diagnosis to be established from the first day of symptoms. Ribavirin may merit consideration in the appropriate clinical setting.

Colorado Tick Fever↗
PubMed1984

Isolation of Eyach virus (Reoviridae, Colorado tick fever group) from Ixodes ricinus and I. ventalloi ticks in France.

During the spring of 1981, two strains of an identical virus were isolated in Mayenne, France, from Ixodes ricinus L. and Ixodes ventalloi Gil Collado, parasiting a wild rabbit (Oryctolagus cuniculus L.). Virological and serological results indicated that these strains belong to the Colorado tick fever serogroup and are indistinguishable from Eyach virus, a tick-borne virus previously described from West Germany. Study of dsRNA PAGE profiles confirmed these conclusions. The morphology and morphogenesis of French isolates were studied in infected suckling mouse brains showing some peculiar features previously described for Colorado tick fever virus. The importance of the isolation of Eyach virus in France is discussed.

Animals↗
PubMed1989

Co-circulation of multiple Colorado tick fever virus genotypes.

Colorado tick fever (CTF) virus, family Reoviridae, genus Orbivirus, contains 12 genes distinguishable by polyacrylamide gel electrophoresis (PAGE). Multiple genotypes of CTF virus were isolated at 3 field sites in Colorado in 1985. Five genotypes were found at Campos Cabin, 2 at Drake, and 6 at Rocky Mountain National Park. Virus isolations were made in 1985 from 6 patients with CTF. These isolates were distinct from each other and the field isolates. Although the CTF isolates were different by PAGE profile, the majority of the 12 genes were highly conserved among the 1985 isolates and a Florio isolate (FMA). Only genes 4 and 6 were variant among the 1985 CTF isolates and FMA, and no unique genes were identified. In 1986, a follow-up field survey was done at the Campos Cabin site. Of the 3 CTF PAGE genotypes obtained, 2 exhibited PAGE profiles which were different from the 1985 isolates. One isolate may have resulted from the reassortment of genes from 2 of the isolates circulating at Campos Cabin in 1985.

Animals↗
PubMed1985

An overview of Colorado tick fever.

Certain features of Colorado tick fever (CTF) virus and the disease it causes may be relevant to studies on bluetongue virus (BTV), or other orbiviruses. Rapid and easy detection of viral antigen in infected tissues and peripheral blood cells by immunofluorescence staining facilitate diagnosis of the disease. The prolonged (3-4 months) viremia is due to persistent intracellular infection, particularly of erythrocytes, in which the virus is protected from antibody or other host defense mechanisms. This results in more efficient maintenance of the virus cycle in nature, but might lead to adverse effects in the human host. Clues to understanding chronic viral infections or viral immunosuppression might be gained by further research on CTF and other orbiviruses.

Animals↗
PubMed2003

Serological evidence of exposure to tick fever organisms in young cattle on Queensland dairy farms.

OBJECTIVES: To compare the features of farms on which the exposure of young cattle to tick fever organisms is sufficient to ensure that immunity is high and the risk of clinical disease is low (endemic stability) with those of farms on which exposure is insufficient to induce widespread immunity (hence without endemic stability); to examine the relationships between the management of ticks and tick fever, and endemic stability to Babesia bovis, B. bigemina and Anaplasma marginale. DESIGN: Cross-sectional study of 874 cattle between the ages of 6 and 15 months on 64 dairy farms, from three centres in south-eastern Queensland (Mutdapilly, Dayboro and Kenilworth) and one centre in far-north Queensland (Malanda). PROCEDURE: Blood samples collected from between 5 and 20 calves from each farm were submitted for serological assay to determine exposure to B. bovis, B. bigemina and A. marginale. A questionnaire about the farm characteristics and the management of ticks and tick fever was completed with each farmer. RESULTS: On 73% of farms, confirmed clinical cases of tick fever were recalled by the farmer, indicating that tick fever was a threat on most farms. The majority of herds in the study (54 of 64) did not have sufficient numbers of seropositive animals aged between 6 and 15 months to have a low risk of tick fever. Region had an effect on the likelihood of endemic stability for all tick fever organisms. Cattle near Malanda in Far-north Queensland were more likely to be seropositive to B. bovis and B. bigemina. The method, strategy and intensity of tick control were not related to the likelihood of endemic stability when the effect of region was considered. The decision to leave a few ticks on cattle in an effort to induce endemic stability did increase the likelihood of endemic stability to A. marginale. However, in practical terms, it was ineffective, because only 26% of these farms had endemic stability against all three organisms. CONCLUSIONS: Given the low proportion of farms that have endemic stability to the tick fever organisms and the high likelihood of clinical disease, vaccination is recommended to protect dairy cattle from tick fever throughout the tick infested area of Queensland. However, further work is required to determine the economic value of vaccination, taking into account the costs of vaccination, of outbreaks and the protective value of vaccination.

Anaplasma marginale↗
PubMed2025

Establishment of reverse genetics systems for Colorado tick fever virus.

The Colorado tick fever virus (CTFV), which has 12-segmented double-stranded RNA genomes, is a pathogenic arbovirus that causes severe diseases in humans. However, little progress has been made in the analysis of replication mechanisms and pathogenicity. This virological constraint is due to the absence of a reverse genetics system for CTFV; therefore, we aimed to establish the system. Initially, the efficacy of CTFV replication was investigated in various cell lines. CTFV was found to grow in many cell types derived from different hosts and organs. Subsequently, BHK-T7 cells stably expressing T7 RNA polymerase were transfected with plasmids encoding each of the 12 CTFV gene segments, expression plasmids encoding all CTFV proteins, and a vaccinia virus RNA-capping enzyme. Following transfection, the cells were co-cultured with Vero or HeLa cells. Using this system, we rescued monoreassortants and recombinant viruses harboring peptide-tagged viral proteins. Furthermore, an improved system using Expi293F cells expressing T7 RNA polymerase was established, which enabled the generation of recombinant reporter CTFVs. In conclusion, these reverse genetics systems for CTFV will greatly contribute to the understanding of viral replication mechanisms, pathogenesis, and transmission, ultimately facilitating the development of rational treatments and candidate vaccines.

Animals↗
PubMed1987

Antigenic variants of Colorado tick fever virus.

Twenty strains of Colorado tick fever (CTF) virus, isolated from ticks, mammals and humans, and two antigenic relatives of CTF virus were compared in cross-neutralization tests. Viruses were tested using single-inoculation sera prepared in hamsters. Antigenic variation, as measured by differences detected in the neutralization test, was noted among the virus isolates identified as strains of CTF virus. The virus strains isolated from humans appeared to vary the most in serological reactions. The two antigenic relatives of CTF virus are clearly distinct from strains of CTF and are different from each other. Antigenic relationships between these two viruses were established using two sets of single-inoculation antisera and both complement fixation and neutralization tests. Six distinct antigenic variants of CTF virus isolated from humans and the virus strain from ticks (75V1906) that showed the least antigenic variation, were tested against 49 coded serum pairs from clinically diagnosed cases of CTF. Significant differences were noted in the number of convalescent-phase sera that reacted with each virus strain and in the number of seroconversions observed with each test virus strain. Convalescent phase sera that reacted with multiple virus strains often varied significantly in antibody titre from one virus strain to another. This indicates that, in some instances, antibody was probably produced in response to infection by different antigenic variants of CTF virus.

Animals↗
PubMed1995

A survey of cattle producers in the Boophilus microplus endemic area of Queensland to determine attitudes to the control of and vaccination against tick fever.

A survey by mail was used to determine the views of beef producers in the Boophilus microplus endemic area of Queensland on the control of and vaccination against tick fever. Data from 448 questionnaires were analysed, representing 2.7% of beef producers in the survey area. Producers considered buffalo fly (Haematobia irritans exigua) infestation as the most important problem whereas tick fever ranked sixth overall. Private veterinarians were regarded as the most important source of information on vaccines for cattle followed by a weekly rural newspaper. From the survey we estimate that about 33% of producers used the tick fever vaccine produced by the Tick Fever Research Centre of Queensland Department of Primary Industries but there were significant (P < 0.05) variations between regions and herds. Large herds (> or = 400 head) in south-east Queensland were the most likely to be vaccinated against tick fever. Of the producers who did not use the vaccine, over 70% replied that there was no need to vaccinate because of the low risk of the disease in their herds. In 52% of unvaccinated herds the treatment of animals with acaricide was considered the most important means of tick fever control and 61% of these herds comprised Bos indicus x Bos taurus or Bos indicus cattle.

Anaplasma↗
PubMed2003

Recombinant VP7-based enzyme-linked immunosorbent assay for detection of immunoglobulin G antibodies to Colorado tick fever virus.

VP6, VP7, VP9, VP10, VP11, and VP12 of Colorado tick fever virus (CTF virus), a virus member of the genus Coltivirus, family Reoviridae, were expressed in bacteria with the pGEX-4T-2 vector. A partial sequence of VP7 (designated pVP7) was chosen to elaborate an enzyme-linked immunosorbent assay (ELISA) for detecting anti-CTF virus immunoglobulin G (IgG) antibodies in humans. This was based on two observations: (i) among all expressed proteins, pVP7 showed the highest immunoreactivity to an anti-CTF virus hyperimmune ascitic fluid; (ii) to provide the highest selectivity of antibody detection, the expressed sequence was chosen within a region which is highly divergent (49% amino acid identity) from the homologous sequence of another coltivirus, the Eyach virus. The pVP7 ELISA was evaluated with 368 serum samples from French blood donors and found to provide 98.1% specificity. Assays with the Calisher set of human serum samples, positive for anti-CTF virus antibodies (C. H. Calisher, J. D. Poland, S. B. Calisher, and L. A Warmoth, J. Clin. Microbiol. 22:84-88, 1985), showed that the pVP7 ELISA provided 100% sensitivity for the tested population. After elaboration of recombinant-protein-based ELISAs for diagnosis of infections with members of the viral genera Orbivirus, Orthoreovirus, and Rotavirus, it was shown that a recombinant protein could be used to detect antibodies to the human pathogen Colorado tick fever virus.

Antibodies, Viral↗
PubMed1985

Virus-induced leukopenia: Colorado tick fever as a human model.

Eight patients with Colorado tick fever were studied to determine whether alterations in the production of granulopoietic stimulatory or inhibitory factors (or both) could be found in association with the leukopenic state of the disease. The studies demonstrate that in the patients with Colorado tick fever the mononuclear cell production of colony-stimulating factor is decreased and that there is an increase in circulating inhibitory factors in the serum of such patients. The depressed mononuclear cell colony-stimulating activity does not appear to be reversible by addition of either endotoxin or normal human serum. Characterization of these serum inhibitory factors may facilitate understanding of leukopenia in human disease.

Adult↗
PubMed1970

White-tailed deer as hosts of cattle fever-ticks.

A penned study for obtaining definitive information on the status of white-tailed deer (Odocoileus virginianus) as a host for cattle feverticks (Boophilus microplus) was conducted on St. Croix of the U.S. Virgin Islands. Four generations of fever-ticks were propagated on one deer during a six month period. Nine wild white-tailed deer also were collected from four insular estates to evaluate the carrier status of these animals on an island where cattle fever-ticks are indigenous. Two deer were infested with B. microplus where contact with domestic livestock had not occurred for 20 years; five deer were free of B. microplus where a vigorous cattle dipping program had been practiced for three years; and, two deer were infested with B. microplus where contact with fever-tick infested cattle occurred at irregular intervals. It was concluded that white-tailed deer constitute a host species for B. microplus and must be considered in future fever tick eradication endeavors. This study also suggested that, through routine dipping of cattle, fever ticks may be eradicated from an area where cattle and deer cohabit the same premises.

Animals↗