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Infection and immunity1985; 49(3); 505-512; doi: 10.1128/iai.49.3.505-512.1985

Ultrastructural study of ehrlichial organisms in the large colons of ponies infected with Potomac horse fever.

Abstract: Potomac horse fever is characterized by fever, anorexia, leukopenia, profuse watery diarrhea, dehydration, and high mortality. An ultrastructural investigation was made to search for any unusual microorganisms in the digestive system, lymphatic organs, and blood cells of ponies that had developed clinical signs after transfusion with whole blood from horses naturally infected with Potomac horse fever. A consistent finding was the presence of rickettsial organisms in the wall of the intestinal tract of these ponies. The organisms were found mostly in the wall of the large colon, but fewer organisms were found in the small colon, jejunum, and cecum. The organisms were also detected in cultured blood monocytes. In the intestinal wall, many microorganisms were intracytoplasmic in deep glandular epithelial cells and mast cells. Microorganisms were also found in macrophages migrating between glandular epithelial cells in the lamina propria and submucosa. The microorganisms were round, very pleomorphic, and surrounded by a host membrane. They contained fine strands of DNA and ribosomes and were surrounded by double bileaflet membranes. Their ultrastructure was very similar to that of the genus Ehrlichia, a member of the family Rickettsiaceae. The high frequency of detection of the organism in the wall of the intestinal tract, especially in the large colon, indicates the presence of organotrophism in this organism. Infected blood monocytes may be the vehicle for transmission between organs and between animals. The characteristic severe diarrhea may be induced by the organism directly by impairing epithelial cell functions or indirectly by perturbing infected macrophages and mast cells in the intestinal wall or by both.
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Publication Date: 1985-09-01 PubMed ID: 4030091PubMed Central: PMC261190DOI: 10.1128/iai.49.3.505-512.1985Google Scholar: Lookup
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Summary

This research summary has been generated with artificial intelligence and may contain errors and omissions. Refer to the original study to confirm details provided. Submit correction.

This study investigated the presence and impact of microscopic organisms, that belong to the Rickettsiaceae family, on ponies suffering from Potomac horse fever. The researchers found these organisms in significant numbers in the intestinal tract of infected ponies, suggesting their role in the pathogenesis of the disease and their potential in transmission between animals.

Details of the Research

  • The researchers embarked on an ultrastructural study on ponies showing clinical signs of Potomac horse fever after receiving blood transfusions from affected horses. This was done to identify any unusual microorganisms that might be associated with the disease.
  • A consistent observation was the presence of rickettsial organisms, related to the genus Ehrlichia, in the intestinal tract of the ponies. Predominantly, these organisms were found in the large colon, with fewer in the small colon, jejunum, and cecum.
  • Apart from the intestinal tract, these organisms were found in additional sites such as in cultured blood monocytes, deep glandular epithelial cells, mast cells and macrophages located in the intestinal wall. This suggests that these cells could play a role in spreading the organism.

Physical Characteristics of the Rickettsial Organisms

  • The rickettsial organisms were observed to be round, very pleomorphic (having a variety of shapes), and surrounded by a host membrane.
  • Internally, they had fine strands of DNA and ribosomes and were encapsulated by double bileaflet membranes. These features are typical of Ehrlichia, members of the Rickettsiaceae family.

Significance of the Findings

  • Given the high rate of detection in the intestinal tract, especially in the large colon, the researchers posit that the rickettsial organisms show significant organotropism – the predisposition of certain pathogenic organisms to infect certain organs more than others.
  • Infected blood monocytes might be instrumental in transferring the microorganisms between organs and also potentially between animals.
  • The substantial diarrhea, characteristic of Potomac horse fever, might be a result of the impairment of epithelial cell functions by the organism, or stimulation of infected macrophages and mast cells in the intestinal wall, or a combination of both.

Cite This Article

APA
Rikihisa Y, Perry BD, Cordes DO. (1985). Ultrastructural study of ehrlichial organisms in the large colons of ponies infected with Potomac horse fever. Infect Immun, 49(3), 505-512. https://doi.org/10.1128/iai.49.3.505-512.1985

Publication

Infection and immunity
ISSN: 0019-9567
NlmUniqueID: 0246127
Country: United States
Language: English
Volume: 49
Issue: 3
Pages: 505-512

Researcher Affiliations

Rikihisa, Y
    Perry, B D
      Cordes, D O

        MeSH Terms

        • Animals
        • Colon / microbiology
        • Ehrlichia / isolation & purification
        • Female
        • Fever / microbiology
        • Fever / veterinary
        • Horse Diseases / microbiology
        • Horse Diseases / pathology
        • Horses
        • Microscopy, Electron
        • Rickettsiaceae / isolation & purification
        • Rickettsiaceae Infections / microbiology
        • Rickettsiaceae Infections / pathology
        • Rickettsiaceae Infections / veterinary

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