Lesions of experimental equine morbillivirus pneumonia in horses.
Abstract: Laboratory examinations of equine morbillivirus included experimental reproductions of the disease caused by the virus by transmission of mixed lung and spleen taken from two field equine cases into two horses and by inoculating tissue culture virus into a further two horses. The most distinctive gross lesions of the diseases that developed in three of the horses was that of pulmonary edema characterized by gelatinous distension of subpleural lymphatics. Histologically, the lesions in the lungs were those of serofibrinous alveolar edema, alveolar macrophages, hemorrhage, thrombosis of capillaries, and syncytial cells. Clearly defined vascular lesions in three horses that became clinically affected within 8 days of inoculation of virus included intramural hemorrhage, edema, and necrosis and syncytial cells in the endothelium of pulmonary vessels (approximately 40-70 microm in diameter). Vascular lesions accompanied by parenchymal degeneration were also seen in the heart, kidney, brain, spleen, lymph node, and stomach. A fourth horse, which survived for 12 days, had detectable lesions only in the lungs, which were more chronic than those in the other three horses, a greater degree of cellular infiltration, and fewer well-defined vascular lesions. Sections stained by an indirect immunocytochemical method showed equine morbillivirus antigen was present in the vascular lesions and along alveolar walls. When endothelial cells were examined by electron microscope, cytoplasmic virus inclusion bodies containing filamentous structures were seen that reacted to an immunogold test to equine morbillivirus antigen. The presence of the syncytia in the small blood vessels in the lungs and other organs was interpreted as an important characteristic of the disease and consistent with a reaction to a morbillivirus.
Publication Date: 1997-07-01 PubMed ID: 9240840DOI: 10.1177/030098589703400407Google Scholar: Lookup
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- Journal Article
Summary
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The study examines the characteristics of the lesions caused by the equine morbillivirus in horses, specifically the distinct features visible in the lungs and other organs of affected animals. The findings provide important insights about the development and severity of the disease over time.
Methods and Procedures
- The researchers recreated the equine morbillivirus disease under controlled laboratory conditions using tissue samples (mixed lung and spleen) from horses that were naturally affected by the virus.
- The disease was transmitted into two healthy horses for observation, and virus sampled from tissue culture was inoculated into two more horses.
Findings: Lesions and Disease Symptoms
- Three of the four horses developed severe symptoms of the disease within 8 days of virus inoculation.
- The horses displayed prominent gross lesions, particularly pulmonary edema, manifested as gelatinous swelling of the lymphatic network found beneath the lung surface.
- At a microscopic level, the lung lesions were characterized by alveolar edema (fluid leakage into the air sacs), immune cells (macrophages), bleeding (hemorrhage), blood clot formation (thrombosis) in capillaries, and formation of multinucleated giant cells (syncytia).
- Vascular damage was also seen in other organs including the heart, kidney, brain, spleen, lymph nodes, and stomach. This was characterized by hemorrhage, swelling (edema), cell death (necrosis), and syncytial cells in the blood vessel lining.
Virus Detection and Localization
- Immunocytochemistry showed the presence of the equine morbillivirus antigen in the vascular lesions and along the alveolar walls.
- Examining the infected endothelial cells under electron microscope revealed virus inclusion bodies (structures containing virus particles) that reacted positively to an immunogold test for the equine morbillivirus antigen.
- These findings confirmed the presence of the virus in the affected blood vessels and lung tissues.
Significance of Observations
- The researchers identified the presence of syncytia (multi-nucleated cells that result from the fusion of several cells together) in the smaller blood vessels of the lungs and other organs as a key characteristic of this disease.
- This specific observation points towards the disease being a reaction to a morbillivirus like the equine morbillivirus.
Case of Delayed Disease Progression
- The fourth horse, which survived for 12 days post-inoculation, showed less severe and more chronic lesions, predominantly only in the lungs.
- There were fewer well-defined vascular lesions, and a greater degree of cellular infiltration, suggesting a slower or less aggressive disease development in this case.
Cite This Article
APA
Hooper PT, Ketterer PJ, Hyatt AD, Russell GM.
(1997).
Lesions of experimental equine morbillivirus pneumonia in horses.
Vet Pathol, 34(4), 312-322.
https://doi.org/10.1177/030098589703400407 Publication
Researcher Affiliations
- CSIRO Australian Animal Health Laboratory, Geelong. peterh@aahl.dah.csiro.gov.au
MeSH Terms
- Animals
- Female
- Horse Diseases / pathology
- Horses
- Kidney / pathology
- Lung / pathology
- Lung / ultrastructure
- Male
- Microscopy, Electron
- Morbillivirus / pathogenicity
- Morbillivirus Infections / pathology
- Morbillivirus Infections / veterinary
- Myocardium / pathology
- Pneumonia / pathology
- Pneumonia / veterinary
- Pneumonia / virology
Citations
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