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Isolation, experimental transmission, and characterization of causative agent of Potomac horse fever.
Abstract: Potomac horse fever, a disease characterized by fever, anorexia, leukopenia, and occasional diarrhea, is fatal in approximately 30 percent of affected animals. The seasonal occurrence of the disease (June to October) and evidence of antibodies to the rickettsia Ehrlichia sennetsu in the serum of convalescing horses suggested that a related rickettsia might be the causative agent. Such an agent was isolated in cultured blood monocytes from an experimentally infected pony. This intracytoplasmic organism was adapted to growth in primary cultures of canine blood monocytes. A healthy pony inoculated with these infected monocytes also developed the disease. The organism was reisolated from this animal which, at autopsy, had pathological manifestations typical of Potomac horse fever. Cross serologic reactions between the newly isolated agent and antisera to 15 rickettsiae revealed that it is related to certain members of the genus Ehrlichia, particularly to Ehrlichia sennetsu. Since the disease occurs in other parts of the United States as well as in the vicinity of the Potomac River, and since it has also been reported in Europe, the name equine monocytic ehrlichiosis is proposed as being more descriptive.
Publication Date: 1985-02-01 PubMed ID: 3880925DOI: 10.1126/science.3880925Google Scholar: Lookup The Equine Research Bank provides access to a large database of publicly available scientific literature. Inclusion in the Research Bank does not imply endorsement of study methods or findings by Mad Barn.
- Journal Article
Summary
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The research paper investigates Potomac horse fever, a lethal disease in horses believed to be caused by a specific type of organism related to rickettsia. By growing the suspected organism in a controlled environment and reintroducing it to a healthy horse, the researchers confirmed its role in the disease development.
Identification and Isolation of Causative Agent
- The research began with the hypothesis that a certain type of rickettsia, a kind of intracellular parasite, is the agent causing Potomac horse fever, a lethal disease found in horses. This conclusion was drawn from the horse’s symptoms and the identification of antibodies in the horse’s blood related to the rickettsia Ehrlichia sennetsu.
- The researchers managed to isolate the suspected organism from monocytes in a blood sample taken from an affected pony. Monocytes are a type of white blood cell that can be infected by rickettsia.
Experimental Testing and Verification
- The isolated rickettsia was then grown in a controlled environment, specifically in cultures of canine monocytes. The growth of this organism outside of a host indicated its ability to survive and multiply in the bloodstream of horses, leading to the disease.
- To confirm the causal relationship, the rickettsia was introduced to a healthy pony. The inoculated pony developed the symptoms and pathologies typical of Potomac horse fever, further confirming that the organism was indeed the cause of the disease.
- The researchers also observed cross-serologic reactions between the newly isolated agent and the antisera to 15 types of rickettsia in horses, revealing that the newly isolated organism was closely related to the Ehrlichia genus, especially to Ehrlichia sennetsu.
Name and Geographical Scope of the Disease
- A more descriptive name, “equine monocytic ehrlichiosis,” was proposed for the disease as it is not confined to the vicinity of the Potomac River in the United States, but affects horses in other parts of the U.S. and Europe.
- The name links the disease to the main type of cell it infects (monocytes), the type of organism that causes it (ehrlichia), and underscores its broad geographical impact.
Cite This Article
APA
Holland CJ, Ristic M, Cole AI, Johnson P, Baker G, Goetz T.
(1985).
Isolation, experimental transmission, and characterization of causative agent of Potomac horse fever.
Science, 227(4686), 522-524.
https://doi.org/10.1126/science.3880925 Publication
Researcher Affiliations
MeSH Terms
- Animals
- Antigens, Bacterial / immunology
- Cells, Cultured
- Cross Reactions
- Ehrlichia / growth & development
- Ehrlichia / immunology
- Ehrlichia / isolation & purification
- Ehrlichia / ultrastructure
- Fluorescent Antibody Technique
- Horse Diseases / blood
- Horse Diseases / microbiology
- Horse Diseases / transmission
- Horses
- Monocytes / microbiology
- Rickettsiaceae / isolation & purification
- Rickettsiaceae Infections / blood
- Rickettsiaceae Infections / microbiology
- Rickettsiaceae Infections / transmission
- Rickettsiaceae Infections / veterinary
- Terminology as Topic
- Vacuoles / ultrastructure
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