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Summary

The effect of prior Rhodococcus equi-induced pneumonia on pulmonary health was investigated in 5 horses (< 24 months old) using endoscopy, radiography, hematologic and bronchoalveolar lavage analyses, and pulmonary function testing. Rhodococcus equi-induced pnuemonia had been diagnosed in principal horses when they were foals. Diagnosis was based on positive results of transtracheal aspiration and thoracic radiography at the time of initial clinical examination. Results of reevalution of the respiratory system of these horses (R + ) were compared with those of 5 age-matched healthy horses (R −) that lacked clinical or historical evidence of foalhood pneumonia.

Significant differences in variables between the 2 groups of horses were not evident. In both groups, most horses had radiographic evidence of an accentuated bronchointerstitial pattern, although results of analysis of bronchoalveolar lavage specimens were normal and mononuclear cells predominated. Variability in results of the pulmonary function tests was observed within and between the 2 groups of horses. Only normalized dynamic lung compliance was slightly lower in the previously infected horses, but this difference was not significant. We concluded that horses previously infected with and successfuly treated for R equi-induced pneumonia do not have detectable evidence of residual lung damage.

Free access
in American Journal of Veterinary Research

SUMMARY

We evaluated the efficacy of 3 treatments for chronic obstructive pulmonary disease in horses: prednisone (400 mg/horse, po, daily; n = 7), methyl sulfonmethane (10 g/horse, po, q 12 h; n = 6), and clenbuterol hydrochloride (0.4 mg/horse, po, q 12 h; n = 7). A fourth group acted as controls (n = 6) and was not treated. The treatment period lasted 10 days. Each horse was a member of 2 different groups for 10 days, separated by an 18-day interval of no treatment. All horses were housed together in an outdoor pen without bedding. Horses were fed alfalfa/grass hay mix ad libitum from a large feeder. The same batch of hay was fed throughout the study. Multiple physical and laboratory variables were monitored prior to, during, and at the end of each 10-day trial period. Changes in lung sounds, respiratory effort, degree of anal movement, nasal discharge, temperature, respiratory rate, or heart rate were not significant. Changes in arterial blood gas tensions, tracheal wash or bronchoalveolar lavage cytologic findings, or phagocyte function were not significant. All horses were tachypneic and most were tachycardic. The median value for Pa o 2 was below normal for all horses. All tracheal wash and most bronchoalveolar lavage cytologic findings represented a suppurative response. Negative linear correlation was observed between Pa o 2 and degree of respiratory effort in these horses (eg,Pa o 2 decreased, the degree of respiratory effort increased).

Free access
in American Journal of Veterinary Research

Summary

Efficacy of sulbactam, a β-lactamase inhibitor, in combination with ampicillin, was evaluated for treatment of experimentally induced pneumonia caused by β-lactam-resistant Klebsiella pneumoniae. Infection was experimentally induced in 18 healthy weanling foals that were randomly allocated to 3 treatment groups: sulbactam plus ampicillin (s/a, 3.3 and 6.6 mg/kg of body weight, respectively), ampicillin (6.6 mg/kg), or vehicle only. Foals were treated daily for 7 days; the observer was unaware of treatment status. Compared with ampicillin and vehicle, treatment with s/a resulted in a statistically significant (P < 0.05) decrease in severity of pneumonia, with regard to bronchoalveolar lavage cytologic findings (decreased total cell and neutrophil numbers, and increased lymphocyte numbers) and extent of macroscopic lesions in lung tissue of the noninoculated regions. Marked trends toward improvement of s/a-treated foals were observed for quantitative results of bacteriologic culture of bronchoalveolar lavage fluid samples (P < 0.07), macroscopic pathologic features of the whole lung (P < 0.1), and histopathologic variables (P < 0.07), compared with ampicillin- and vehicle-treated foals. Treatment effects were not observed for radiographic, hematologic, and blood gas abnormalities that resulted from infection. In conclusion, the combination of sulbactam plus ampicillin was found to have synergistic effects in vivo, to reduce the extent and severity of experimentally induced gram-negative lung infection in foals.

Free access
in American Journal of Veterinary Research

Abstract

Objective

To characterize surfactant protein isolated from bronchoalveolar lavage fluids of healthy horses.

Animals

10 Thoroughbreds (5 males, 5 females; 26 to 40 months old) that did not have a history or clinical signs of respiratory tract disease.

Procedure

Bronchoalveolar lavage fluid (BALF) was obtained and centrifuged at 33,000 × g. Lipid was removed from precipitated fractions by means of extraction with 1-butanol, and organic solvent-insoluble protein precipitates were dialyzed against Tris buffer. The suspension was centrifuged, and supernatant was placed in a mannose-Sepharose affinity column, with calcium. The bound protein fraction was analyzed by means of sodium dodecyl sulfate-polyacrylamide gel electrophoresis, western immunoblot analysis, and amino acid sequencing. A liposome-aggregation assay was also performed, using purified proteins.

Results

Protein isolated by use of mannose-affinity matrices was identified as surfactant protein A (SP-A). It had carbohydrate-binding and phospholipid-aggregation properties characteristic of SP-A isolated from other animal species. The partial primary sequence of the isolated protein had high homology with rat and human SP-A. Furthermore, the equine SP-A reacted with anti-human and anti-rat SP-A specific antibodies.

Conclusion

Analysis of these findings indicated the existence of SP-A in pulmonary tissues of horses.

Clinical Relevance

Measurement of SP-A concentrations may be useful for clinicians evaluating pulmonary disease of horses. (Am J Vet Res 1999;60: 169-173)

Free access
in American Journal of Veterinary Research

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.

Free access
in American Journal of Veterinary Research

SUMMARY

Alpha 2-(β1-glycoprotein may be found free in horse serum or complexed with α-1-proteinase inhibitor to form pre-α2-elastase inhibitor. There has been little information published concerning α2-β1-glycoprotein and its possible tissue sources in horses. A peroxidase-antiperoxidase technique was used to identify α2-(β1 -glycoprotein in buffy coat and bone marrow neutrophils of healthy horses. Macrophages and neutrophils in bronchoalveolar lavage samples from clinically normal horses and from horses with chronic pulmonary disease also were positive for α2-(β1-glycoprotein. Alpha 2-β1-glycoprotein was identified in some instances in normal equine hepatocytes of formalin- fixed liver sections. In formalin-fixed lung sections from horses with chronic, small-airway disease and chronic bronchointerstitial pneumonia, α2-β1-glycoprotein was observed in some airway secretions and in macrophages.

Free access
in American Journal of Veterinary Research

Abstract

Objectives

To determine whether tilmicosin alters neutrophil infiltration or function, induces neutrophil apoptosis, and affects accumulation of leukotriene B4 (LTB4) or tumor necrosis factor-alpha (TNF-α) in lungs of calves experimentally infected with Pasteurella haemolytica.

Animals

12 weight-ranked Holstein calves.

Procedure

Calves were given 25% propylene glycol vehicle (n = 5) or tilmicosin (10 mg/kg of body weight; n = 6) subcutaneously, 18 hours and 15 minutes before intratracheal infection with 2 × 108 P haemolytica organisms. Two unmanipulated calves served as controls in some experiments. Rectal temperatures were recorded 15 minutes before, and at 3- hour intervals after infection for 24 hours. Samples obtained from bronchoalveolar lavage performed 3 and 24 hours after infection were used to assess colonization by P haemolytica, and neutrophil infiltration. Neutrophil phagocytosis of P haemolytica, membrane leakage as determined by trypan blue exclusion, oxidative function as determined by nitro blue tetrazolium reduction, and apoptosis, using electron microscopy and DNA fragmentation ELISA, were determined. Soluble TNF-α and LTB4 were measured from supernatants from bronchoalveolar lavage samples, using ELISA.

Results

Treatment with tilmicosin resulted in significant (P< 0.05) clearance of P haemolytica and neutrophil apoptosis at 3 hours, and decreased concentration of LTB4 at 24 hours. Rectal temperatures, neutrophil infiltration, phagocytosis, oxidative functions, membrane leakage, and soluble TNF-α concentrations were not significantly affected by tilmicosin.

Conclusion

Tilmicosin effectively controlled P haemolytica infection, induced neutrophil apoptosis, reduced pulmonary inflammation, and did not affect neutrophil infiltration or function.

Clinical Relevance

By inducing neutrophil apoptosis, tilmicosin prevents further amplification of inflammatory injury in P haemolytica-infected lungs. (Am J Vet Res 1998;59:765-771)

Free access
in American Journal of Veterinary Research

Abstract

Objective

To investigate the effects of ozone and airway inflammation on indices of oxidant injury in horses.

Animals

5 clinically normal horses and 25 horses referred for poor performance

Procedure

Blood, tracheal wash, and bronchoalveolar lavage fluid samples were collected before and after ozone exposure (n = 5) or from clinical cases (n = 25), and were analyzed for reduced glutathione (GSH), glutathione disulfide (GSSG), and free and total iron (Fe) values. A scor ing system (0 to 5) was used to assess airway inflammation on the basis of clinical signs and cytologic analysis of the tracheal wash and bronchoalveolar lavage fluid samples.

Results

Ozone induced significant (P < 0.05) increases in GSH (195.4 ± 68.5 μM, GSSG (19.4 ± 6.4 μM). and free (25.5 ± 16.1 μM) and total (93.1 ± 13.4 μM) Fe values in the pulmonary epithelial lining fluid, compared with preozone samples (49.2 ± 18.6, 2.4 ± 1.2, 0.0, and 33.1 ± 5.9 μM, respectively). The presence of airway inflammation (19/25) was associated with high GSSG and free and total Fe, but not GSH, values in epithelial lining fluid, compared with values for clinically normal horses (6/25). There were no differences in the systemic values of GSH, GSSG, and free and total Fe between any of the groups. A strong correlation (r = 0.84; P < 0.001) existed between inflammation score and the glutathione redox ratio (GSSG/IGSH + GSSG]) in the 25 horses admitted for clinical examination

Conclusions

Oxidant injury in the lung will induce changes in the glutathione status and Fe homeostasis that could affect pathogenesis of the disease.

Clinical Relevance

Measurement of indices of oxidant injury may be useful in the diagnosis of airway inflammation and the response to inhaled oxidants. (Am J Vet Res 1996;57:1359-1363)

Free access
in American Journal of Veterinary Research

Abstract

Objective

To assess shedding of ovine lentivirus (OvLV) in semen of infected rams with or without epididymitis.

Design

Rams 1 and 2 were naturally infected with OvLV. Rams 3-6 were inoculated with OvLV strain 85/ 34. Ram 7 was inoculated with uninfected cell culture supernatatant (OvLV-negative control). 14 weeks after OvLV inoculation, rams 1-3, 6, and 7 were inoculated with Brucella ovis into the epididymis. Ram 4 was a natural case of B ovis epididymitis, and ram 5 was left non-inoculated (Bovis-negative control). Blood mononuclear cells (BMNC) and semen were collected between 0 and 44 weeks after OvLV inoculation.

Animals

Seven 2- to 3-year-old rams.

Procedure

Infective OvLV in BMNC and semen was determined by virus isolation and subsequent OvLV-DNA amplification by polymerase chain reaction (PCR). Bronchoalveolar lavage cells collected after death were used for DNA extraction and PCR amplification.

Results

OvLV was detected in the semen of rams 3 and 6, but only after Bovis inoculation. OvLV was isolated consistently from BMNC of rams 3 and 6, but only occasionally from rams 1, 2, 4, and 5. Leukocytospermia was evident in every ejaculate of all Bovis-infected rams after infection. Semiquantitative PCR determination of OvLV DNA from bronchoalveolar lavage cells revealed the highest OvLV DNA load in rams 3 and 6.

Conclusions

Leukocytospermia and a high virus load in infected animals are important factors that determine shedding of OvLV in semen.

Clinical Relevance

Dissemination of OvLV through contaminated semen could have important implications in the epidemiology and control of this infection. (Am J Vet Res 1996; 57:684–688)

Free access
in American Journal of Veterinary Research

Abstract

Objective—To compare results of intradermal tests (IDT), conducted using environmental allergens, in horses without atopy and horses with chronic obstructive pulmonary disease (COPD).

Animals—38 horses (22 horses without atopy and 16 horses with COPD).

Procedure—All horses were examined (physical examination, hematologic examination, serum biochemical analyses, examination of bronchoalveolar lavage fluid). An IDT was conducted, using a full panel of 73 allergens consisting of grasses, weeds, trees, molds, and insects. Results of the IDT were evaluated 30 minutes and 4, 6, and 24 hours after injection of allergens. Horses without atopy were euthanatized, and gross and histologic changes of lung parenchyma were assessed.

Results—Horses without atopy had a greater number of positive immediate and late-phase reactions than did horses with COPD. Horses with COPD did not have a significantly greater number of positive reactions than horses without atopy at any time period for any allergen group (grasses, weeds, trees, molds, and insects).

Conclusions and Clinical Relevance—Positive results of IDT document allergen-specific hypersensitivity but do not necessarily distinguish clinically relevant reactions from subclinical reactivity in horses with COPD. Interpreting the clinical relevance of results of IDT requires a thorough knowledge of the medical history, physical examination findings, and environment of each animal. (Am J Vet Res 2001;62:389–397)

Full access
in American Journal of Veterinary Research