Oral transmission of Ehrlichia risticii resulting in Potomac horse fever

1988 ◽  
Vol 122 (26) ◽  
pp. 635-635 ◽  
Author(s):  
J. Palmer ◽  
C. Benson
Keyword(s):  
Oral Transmission ◽  
Potomac Horse Fever ◽  
Ehrlichia Risticii

Infection rate of Ehrlichia risticii, the agent of Potomac horse fever, in freshwater stream snails (Juga yrekaensis) from northern California

2000 ◽  
Vol 92 (2) ◽  
pp. 151-156 ◽  
Author(s):  
Nicola Pusterla ◽  
Eileen Johnson ◽  
Joon-seok Chae ◽  
Jeannine Berger Pusterla ◽  
Elfriede DeRock ◽  
...  
Keyword(s):  
Infection Rate ◽  
Northern California ◽  
Potomac Horse Fever ◽  
Freshwater Stream ◽  
Ehrlichia Risticii

Detection of Ehrlichia risticii, the Agent of Potomac Horse Fever, in Freshwater Stream Snails (Pleuroceridae:Juga spp.) from Northern California

1998 ◽  
Vol 64 (8) ◽  
pp. 2888-2893 ◽  
Author(s):  
Jeffrey E. Barlough ◽  
Gerhard H. Reubel ◽  
John E. Madigan ◽  
Larisa K. Vredevoe ◽  
Paul E. Miller ◽  
...  
Keyword(s):  
Life Cycle ◽  
Heat Shock ◽  
16S Rrna ◽  
Stream Water ◽  
Northern California ◽  
Source Organism ◽  
Potomac Horse Fever ◽  
Freshwater Stream ◽  
Ehrlichia Risticii ◽  
Major Antigen

ABSTRACT Ehrlichia DNA was identified by nested PCR in operculate snails (Pleuroceridae: Juga spp.) collected from stream water in a northern California pasture in which Potomac horse fever (PHF) is enzootic. Sequencing of PCR-amplified DNA from a suite of genes (the 16S rRNA, groESL heat shock operon, 51-kDa major antigen genes) indicated that the source organism closely resembledEhrlichia risticii, the causative agent of PHF. The minimum percentage of Juga spp. harboring the organism in the population studied was 3.5% (2 of 57 snails). No ehrlichia DNA was found in tissues of 123 lymnaeid, physid, and planorbid snails collected at the same site. These data suggest that pleurocerid stream snails may play a role in the life cycle of E. risticii in northern California.

Isolation of Ehrlichia risticii, the causative agent of Potomac horse fever, from the fetus of an experimentally infected mare

1987 ◽  
Vol 121 (10) ◽  
pp. 232-232 ◽  
Author(s):  
J. Dawson ◽  
M. Ristic ◽  
C. Holland ◽  
R. Whitlock ◽  
J. Sessions
Keyword(s):  
Causative Agent ◽  
Potomac Horse Fever ◽  
Ehrlichia Risticii

Transmission of Ehrlichia risticii, the agent of Potomac horse fever, using naturally infected aquatic insects and helminth vectors: preliminary report

2000 ◽  
Vol 32 (4) ◽  
pp. 275-279 ◽  
Author(s):  
J. E. Madigan ◽  
N. Pusterla ◽  
E. Johnson ◽  
J.-S. Chae ◽  
J. Berger Pusterla ◽  
...  
Keyword(s):  
Aquatic Insects ◽  
Preliminary Report ◽  
Potomac Horse Fever ◽  
Ehrlichia Risticii

scholarly journals Production and Characterization of Ehrlichia risticii, the Agent of Potomac Horse Fever, from Snails (Pleuroceridae: Juga spp.) in Aquarium Culture and Genetic Comparison to Equine Strains

1998 ◽  
Vol 36 (6) ◽  
pp. 1501-1511 ◽  
Author(s):  
Gerhard H. Reubel ◽  
Jeffrey E. Barlough ◽  
John E. Madigan
Keyword(s):  
Genetic Information ◽  
Phylogenetic Analyses ◽  
Collection Site ◽  
Source Organism ◽  
Potomac Horse Fever ◽  
Ehrlichia Risticii ◽  
Major Antigen ◽  
Stream Waters ◽  
Genetic Comparison

We report on the production and characterization of Ehrlichia risticii, the agent of Potomac horse fever (PHF), from snails (Pleuroceridae: Juga spp.) maintained in aquarium culture and compare it genetically to equine strains. Snails were collected from stream waters on a pasture in Siskiyou County, Calif., where PHF is enzootic and were maintained for several weeks in freshwater aquaria in the laboratory. Upon exposure to temperatures above 22°C the snails released trematode cercariae tentatively identified as virgulate cercariae. Fragments of three different genes (genes for 16S rRNA, thegroESL heat shock operon, and the 51-kDa major antigen) were amplified from cercaria lysates by PCR and sequenced. Genetic information was also obtained from E. risticii strains from horses with PHF. The PCR positivity of snail secretions was associated with the presence of trematode cercariae. Sequence analysis of the three genes indicated that the source organism closely resembledE. risticii, and the sequences of all three genes were virtually identical to those of the genes of an equine E. risticii strain from a property near the snail collection site. Phylogenetic analyses of the three genes indicated the presence of geographical E. risticii strain clusters.

scholarly journals Association of Deficiency in Antibody Response to Vaccine and Heterogeneity of Ehrlichia risticii Strains with Potomac Horse Fever Vaccine Failure in Horses

1998 ◽  
Vol 36 (2) ◽  
pp. 506-512 ◽  
Author(s):  
Sukanta K. Dutta ◽  
Ramesh Vemulapalli ◽  
Biswajit Biswas
Keyword(s):  
Antibody Response ◽  
Protective Antigen ◽  
Specific Antigen ◽  
Clinical Signs ◽  
Neutralizing Antibody ◽  
Original Strain ◽  
Vaccine Failure ◽  
Potomac Horse Fever ◽  
Ehrlichia Risticii

Ehrlichia risticii is the causative agent of Potomac horse fever (PHF), which continues to be an important disease of horses. Commercial inactivated whole-cell vaccines are regularly used for immunization of horses against the disease. However, PHF is occurring in large numbers of horses in spite of vaccination. In a limited study, 43 confirmed cases of PHF occurred between the 1994 and 1996 seasons; of these, 38 (89%) were in horses that had been vaccinated for the respective season, thereby clearly indicating vaccine failure. A field study of horses vaccinated with two PHF vaccines indicated a poor antibody response, as determined by immunofluorescence assay (IFA) titers. In a majority of horses, the final antibody titer ranged between 40 and 1,280, in spite of repeated vaccinations. None of the vaccinated horses developed in vitro neutralizing antibody in their sera. Similarly, one horse experimentally vaccinated three times with one of the vaccines showed a poor antibody response, with final IFA titers between 80 and 160. The horse did not develop in vitro neutralizing antibody or antibody against the 50/85-kDa strain-specific antigen (SSA), which is the protective antigen of the original strain, 25-D, and the variant strain of our laboratory, strain 90-12. Upon challenge infection with the 90-12 strain, the horse showed clinical signs of the disease. The horse developed neutralizing antibody and antibody to the 50/85-kDa SSA following the infection. Studies of the new E. risticiiisolates from the field cases indicated that they were heterogeneous among themselves and showed differences from the 25-D and 90-12 strains as determined by IFA reactivity pattern, DNA amplification finger printing profile, and in vitro neutralization activity. Most importantly, the molecular sizes of the SSA of these isolates varied, ranging from 48 to 85 kDa. These studies suggest that the deficiency in the antibody response to the PHF vaccines and the heterogeneity ofE. risticii isolates may be associated with the vaccine failure.

scholarly journals Helminthic Transmission and Isolation of Ehrlichia risticii, the Causative Agent of Potomac Horse Fever, by Using Trematode Stages from Freshwater Stream Snails

2000 ◽  
Vol 38 (3) ◽  
pp. 1293-1297 ◽  
Author(s):  
Nicola Pusterla ◽  
John E. Madigan ◽  
Joon-Seok Chae ◽  
Elfriede DeRock ◽  
Eileen Johnson ◽  
...  
Keyword(s):  
Causative Agent ◽  
Monocytic Cells ◽  
Potomac Horse Fever ◽  
Freshwater Stream ◽  
Ehrlichia Risticii

We report successful helminthic transmission of Ehrlichia risticii, the causative agent of Potomac horse fever, using trematode stages collected from Juga yrekaensis snails. The ehrlichial agent was isolated from the blood of experimentally infected horses by culture in murine monocytic cells and identified as E. risticii ultrastructurally and by characterization of three different genes.

scholarly journals The tribe Ehrlichieae and ehrlichial diseases.

1991 ◽  
Vol 4 (3) ◽  
pp. 286-308 ◽  
Author(s):  
Y Rikihisa
Keyword(s):  
Systemic Disease ◽  
The United States ◽  
Cross Reactivity ◽  
Etiologic Agent ◽  
16S Rrna Sequence ◽  
Intracellular Parasites ◽  
Potomac Horse Fever ◽  
Ehrlichia Risticii ◽  
16S Rrna Sequence Analysis ◽  
Human Ehrlichiosis

The tribe Ehrlichieae consists of gram-negative minute cocci that are obligate intracellular parasites classified in the family Rickettsiaceae. Although ehrlichial organisms have been observed in leukocytes for many years, only a few species have been cultured in quantities sufficient for biochemical and molecular analyses. Recents studies on 16S-rRNA sequence analysis and energy metabolism showed that the genus Ehrlichia is closely related to the genus Rickettsia. There is, however, no antigenic cross-reactivity between these genera. Ehrlichial organisms cause a disease called "ehrlichiosis," a noncontagious infectious disease known to be transmitted by a tick in several cases and by a fluke in one case. Ehrlichia spp. infect dogs, ruminants, horses, and humans. Recently, two new ehrlichial diseases, Potomac horse fever and human ehrlichiosis, were discovered in the United States. The etiologic agent of Potomac horse fever, Ehrlichia risticii, is closely related to the known human pathogen Ehrlichia sennetsu. The etiologic agent of human ehrlichiosis is related to Ehrlichia canis, a canine pathogen. In contrast to the genus Rickettsia, members of the tribe Ehrlichieae reside primarily in the cytoplasmic vacuoles of monocytes or granulocytes and cause hematologic abnormalities, lymphadenopathy, and other pathologic changes in the host. However, the actual mechanisms whereby Ehrlichia spp. infect leukocytes, multiply in them, and produce various forms of systemic disease have not been defined. Depending on the ehrlichial species involved, serologic or direct microscopic observation of stained blood smears is currently used to diagnose ehrlichial disease.

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