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- Author or Editor: Roland von Fellenberg x
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Abstract
Objective—To analyze effects of hay dust exposure on interleukin-8 (IL-8) concentration, percentage of neutrophils, and neutrophil chemotactic activity in bronchoalveolar lavage fluid (BALF) of horses with chronic obstructive pulmonary disease (COPD).
Animals—16 healthy horses and 29 horses with COPD.
Procedure—IL-8 concentration, percentage of neutrophils, and neutrophil chemotactic activity in BALF were measured. Values were analyzed with respect to hay dust exposure. These variables were also measured in 5 asymptomatic horses with COPD after the induction of clinical signs by changing feed from silage to hay.
Results—IL-8 concentrations and chemotactic activity in BALF were greater in horses with COPD, compared with healthy horses, and greater in horses with COPD exposed to hay dust, compared with nonexposed affected horses. An increase in IL-8 concentration accompanied by an increase in percentage of neutrophils in BALF and development of clinical signs of COPD were induced in asymptomatic horses with COPD by changing feed from silage to hay.
Conclusions and Clinical Relevance—Exposure of horses with COPD to hay dust components resulted in an increase in IL-8 secretion at the bronchoalveolar surface. This chemokine may play a role in the pathogenesis of COPD, because it causes neutrophil accumulation in the bronchoalveolar space. Our results underscore the importance of eliminating dust sources for the treatment and prevention of COPD in horses. (Am J Vet Res 2000;61:1369–1374)
SUMMARY
In a search of viral agents in pulmonary macrophages of horses with chronic pulmonary disease, equine herpesvirus 2 was found to be unique. In 8 of 9 horses with chronic pulmonary disease, antigens of equine herpesvirus 2 were detected by indirect immunofluorescence staining of scattered foamy macrophages immediately after harvesting by bronchoalveolar lavage and fractionation on metrizamide gradients. In a healthy horse, antigens were not found. After 1 week of cultivation of bronchoalveolar lavage cells from a second group of 9 horses with chronic pulmonary disease, viral antigens were detected in 90% of the adherent pulmonary macrophages. In 2 of 3 healthy horses, viral antigens also were found in 90% of the adherent pulmonary macrophages. Antigens of equine herpesvirus 1, equine herpesvirus 4, parainfluenza virus 3, or adenovirus were not detected. Antigens of the 5 investigated viruses also were not detected in lung tissue slices from a third group of 14 horses: 4 healthy; 7 with varying degrees of bronchiolitis, 2 of which also had chronic intestitial pneumonia; 2 with eosinophilic bronchitis; and 1 with pulmonary hemorrhage.
The exclusive presence of equine herpesvirus 2 in pulmonary macrophages was confirmed qualitatively by isolation of infective virus by cocultivation. In a fourth group of 12 horses with chronic pulmonary disease, infective virus could be isolated from pulmonary macrophages of 3 horses and from mixed- blood leukocytes of 5 horses. Virus isolations from 2 healthy horses were not successful from pulmonary macrophages, whereas 1 isolation was obtained from mixed-blood leukocytes. Other viruses were not detected by cocultivation.