Effect of long-term fluticasone treatment on immune function in horses with heaves

Background: Corticosteroids currently are the most effective pharmacological treatment available to control heaves in horses. Systemically administered corticosteroids have been shown to alter immune response in horses, humans, and other species. Aerosolized administration theoretically minimizes systemic adverse effects, but the effect of inhaled corticosteroids on immune function has not been evaluated in horses. Objectives: To evaluate the effects of prolonged administration of inhaled fluticasone on the immune system of heaves‐affected horses. Animals: Heaves‐affected horses were treated with inhaled fluticasone (n = 5) for 11 months or received environmental modifications only (n = 5). Methods: Prospective analysis. Clinical parameters and CBC, lymphocyte subpopulations and function, and circulating neutrophil gene expression were sequentially measured. Primary and anamnestic immune responses also were evaluated by measuring antigen‐specific antibodies in response to vaccination with bovine viral antigen and tetanus toxoid, respectively. Results: No clinical adverse effects were observed and no differences in immune function were detected between treated and untreated horses. Conclusions and Clinical Importance: The treatment of heaves‐affected horses with inhaled fluticasone at therapeutic dosages for 11 months has no significant detectable effect on innate and adaptive (both humoral and cell‐mediated) immune parameters studied. These results suggest that prolonged administration of fluticasone would not compromise the systemic immune response to pathogens nor vaccination in adult horses.     

Bronchodilator activity of the selective muscarinic antagonist revatropate in horses with heaves

Bronchodilators are frequently used to attenuate airway obstruction in equine heaves (or recurrent airway obstruction). This study evaluated the selective (M₃ and M₁) muscarinic antagonist revatropate, which offers potential advantages over non-specific antimuscarinic agents such as ipratropium. Protocol 1 assessed the response to inhaled revatropate (1, 2 and 7 mg) using a blinded, negative (inhaled saline) and positive (inhaled ipratropium bromide; 0.3, 0.7 and 2 mg) controlled, dose escalation study, with six heaves horses. The lowest doses of revatropate and ipratropium induced a rapid (within 1 h) and significant improvement in airway function. The highest doses of both drugs had no significant effect on gastrointestinal sound score or iris function, but resulted in tacky mucous membranes and reduced gastrointestinal sound score in some horses.In Protocol 2, a cross-over design comparing the duration of action of inhaled revatropate (1 mg), ipratropium (0.3 mg) and saline, some indices of airway function were improved for between 5 and 6 h after revatropate administration, and for between 6 and 24 h after ipratropium administration. Inhaled revatropate and ipratropium had similar effects on airway function, with no significant difference between their efficacies. Importantly, however, only revatropate significantly improved clinical scores of breathing effort, improving combined clinical score at the 1 h time point and abdominal score at the 1–3 h time points. No significant adverse events were observed in Protocol 2, although some horses had reduced gastrointestinal sound scores. Inhaled revatropate is therefore a safe and effective bronchodilator for treating airway obstruction in heaves.     

Trimetoquinol: bronchodilator effects in horses with heaves following aerosolised and oral administration

REASON FOR PERFORMING STUDY: The bronchodilator effects of trimetoquinol (TMQ) have been studied when administered i.v. or intratracheally, but not in an aerosolised form. OBJECTIVES: To define the relationship between the therapeutic and adverse responses (therapeutic index) of TMQ when administered as an aerosol or by the oral route. METHODS: Increasing doses of TMQ were administered to horses with heaves as an aerosol and by the oral route. Dose ranged 100-1000 microg/horse for aerosolised TMQ and from 6-60 microg/kg bwt for the oral route. Airway and cardiac effects were assessed by measurement of maximal change in pleural pressure (deltaPplmax) and heart rate (HR), respectively. Side effects of sweating, agitation and muscle trembling were scored subjectively. Duration of action of aerosolised (1000 pg/horse) and oral (6-60 microg/kg bwt) TMQ was evaluated over 6 h. RESULTS: Aerosol administration of TMQ caused dose-dependent bronchodilation but did not change HR or cause other observable side effects. When 1000 microg/horse was administered via aerosol, TMQ produced a 2-phase bronchodilation; an immediate effect lasting up to 30 min and a second phase between 2 and 4 h. Oral TMQ was therapeutically ineffective. CONCLUSION: Aerosol administration of TMQ is a safe and effective method of producing bronchodilation in horses.     

Pulmonary and systemic effects of inhaled endotoxin in control and heaves horses

To investigate whether inhaled endotoxin contributes to airway inflammation and dysfunction in stabled horses, control (n = 6) and asymptomatic heaves (previously termed chronic obstructive pulmonary disease)-susceptible (n = 7) horses were given inhalation challenges with 20, 200 and 2,000 microg of soluble Salmonella typhimurium Ra60 lipopolysaccharide (LPS). LPS inhalation induced a dose-dependent neutrophilic airway inflammatory response in both groups. Inhalation with 2,000 microg of LPS also induced detectable lung dysfunction in the heaves group. LPS inhalation did not alter clinical score, tracheal secretion volume or airway reactivity in either group. The no-response thresholds were lower for the heaves group (<20 microg for airway inflammation; 200 to 2,000 microg for lung dysfunction) than for the control group (20 to 200 microg for airway inflammation; >2,000 microg for lung dysfunction). To enable comparison of these threshold levels with airborne endotoxin concentrations in stables, horses also received a 5 h duration hay/straw challenge, during which the total and respirable airborne endotoxin concentrations were determined. Comparison of the effects of acute LPS inhalation and hay/straw challenges suggest that inhaled endotoxin is not the sole cause of heaves. However, it is likely that it contributes to airway inflammation, both in heaves horses in concert with other inhalants, and in normal horses when they are exposed to high levels in poor stable environments.     

Cytokine induction in pulmonary airways of horses with heaves and effect of therapy with inhaled fluticasone propionate

Work in humans and laboratory animals has identified a central role for cytokines and chemokines in development and persistence of lower airway inflammation. The objectives of this study were to determine interleukin (IL)-1 beta, IL-2, IL-4, IL-5, IL-6, IL-8, IL-10, interferon (IFN)-gamma and tumor necrosis factor (TNF)-alpha induction in bronchoalveolar lavage (BAL) of control horses and horses with heaves both during remission and exacerbation of the disease, and to determine the effect of therapy with inhaled fluticasone propionate on the cytokine profile of horses with heaves. IL-1 beta and TNF-alpha mRNA expression was significantly higher in horses with heaves after exposure to moldy hay compared to either values obtained during clinical remission or to healthy controls. IL-8 mRNA expression and protein concentrations were significantly higher in horses with heaves than in controls. Both IL-4 and IFN-gamma mRNA expression was increased at various times in heaves-susceptible horses compared to controls. IL-2, IL-5 and IL-10 mRNA expression was not detected in BAL cells of either group. Therapy with inhaled fluticasone propionate after induction of a severe heaves exacerbation resulted in complete resolution of clinical signs, normalization of pulmonary function tests, and significant decrease in BAL neutrophilia. This was associated with a significant decrease in IL-4 mRNA expression and increase in IFN-gamma/IL-4 ratio in horses with heaves. These results demonstrate the clinical efficacy of inhaled fluticasone propionate for the treatment of heaves and suggest a role for cytokines in the development of lower airway inflammation in heaves-susceptible horses.     

Efficacy of three corticosteroids for the treatment of heaves

This study used a cross-over design to compare the efficacy of 3 corticosteroids for the relief of airway obstruction and inflammation in 9 heaves-affected horses. The severity of airway obstruction and inflammation was quantified by measurement of lung function and by bronchoalveolar lavage fluid (BALF) cytology, respectively. Airway obstruction was induced by stabling the horses and they remained stabled during the 10 day treatment period. Lung function was measured before treatment (baseline), at Days 3, 7, and 10 of treatment, and after 30 days at pasture. BALF cytology was investigated at baseline, Day 10, and at pasture. All 9 horses received the following 4 treatments in random order: no treatment, daily oral prednisone tablets (1 mg/kg), daily i.v. dexamethasone solution (0.1 mg/kg), and i.m. dexamethasone-21-isonicotinate (0.04 mg/kg) every 3 days. When horses received no treatment, lung function did not change significantly during stabling but improved at pasture. In all horses, daily i.v. administration of dexamethasone solution improved lung function within 3 days to levels as good as or better than those measured at pasture. Dexamethasone-21-isonicotinate was rapidly effective in 8 of 9 horses. The other horse did not respond to this drug. Prednisone tablets were without effect on Days 3 and 7 of treatment, but by Day 10, 5 of 9 horses showed some improvement in lung function. Dexamethasone i.v. solution decreased the percent neutrophils in BALF at Day 10. Other treatments had no effect on BALF cytology. These results demonstrate that dexamethasone rapidly relieved airway obstruction in heaves-affected horses. Oral prednisone had inconsistent effects but may be beneficial in some horses after more than a week of treatment.     

Comparison of TGF-beta 1 concentrations in bronchoalveolar fluid of horses affected with heaves and of normal controls

Airway remodeling may play an important role in heaves pathophysiology. Transforming growth factor-beta 1 (TGF-beta1) is a potent profibrotic cytokine, which might contribute to airway wall thickening and fibrosis of bronchiolar and alveolar submucosa. An ELISA designed for the measurement of human TGF-beta1 was used to measured total TGF-beta1 released in bronchoalveolar lavage fluid (BALF) of normal horses and of those affected with heaves in remission. The specificity of the assay for TGF-beta1 of the horse was confirmed using recombinant equine TGF-beta1. The influence of hay exposure on TGF-beta1 release in the airways was also examined by stabling horses in a dusty environment. TGF-beta1 was found in the BALF of all horses. However, no significant difference between basal concentration of TGF-beta1 in BALF of control horses versus that of horses affected with heaves was found. Furthermore, no differences were identified in these populations 1 and 9 days after allergen challenge. In conclusion, these data indicate that TGF-beta1 is released in BALF fluid of horses in biologically active concentrations. Other studies are necessary for a better definition of the role of this cytokine within the lung, as our study does not establish a causal relationship between TGF-beta1 and the pathophysiology of heaves in the horse.     

Cytokine mRNA expression of pulmonary macrophages varies with challenge but not with disease state in horses with heaves or in controls

Heaves in horses is characterized by lower airway neutrophilic inflammation, and reversible airflow obstruction. Pulmonary macrophages contribute to the inflammation observed in a number of human and animal pulmonary diseases, and it has been postulated that they are responsible for the neutrophilic inflammation present in heaves by the release of cytokines and chemokines. To test this hypothesis, the mRNA expression of TNF-α, IL-1β, IL-8, and MIP-2 by macrophages isolated from bronchoalveolar lavage cells was quantified using real-time RT-PCR in horses with heaves (n-6) and controls (n-6). Animals were studied after being pastured for 3 months to induce clinical remission of heaves, and after 24h, and 9 days of a continuous natural antigen challenge consisting of hay feeding and straw bedding. The study was performed during 2 consecutive summers, when 3 horses with heaves and 3 control horses were evaluated. As expected, airway obstruction developed with the challenge only in horses with heaves, while airway neutrophilia was observed in both groups of horses. Stabling resulted in an increased expression of IL-8/?-actin and MIP-2/?-actin after 24h of stabling in both groups of horses. Further analyses revealed that compared to pasture, the expression of these chemokines was significantly increased after 24h of stabling only in Year 1, while the IL-8 expression was significantly decreased at 9 days in Year 2. No significant group, time, or year differences in IL-1β/?-actin and TNF-α/?-actin ratio were observed. The expression of IL-1β was strongly correlated with neutrophil percentages, although at different time points in the two study-years. These results suggest that alveolar macrophages can contribute to the airway inflammation resulting from stabling in horses by the release of IL-8 and MIP-2, but that the release of these chemokines is unlikely to be responsible for the marked airway neutrophilia observed in heaves. The variable expression of IL-8 and MIP-2 by alveolar macrophages between the two-study years are additional novel findings highlighting the complexity of the inflammatory pathways associated with airway inflammation and the importance of evaluating concurrently horses with heaves and controls to ensure identical environmental challenges.     

Influenza hemagglutination inhibiting activity in respiratory mucus from horses with chronic obstructive pulmonary disorders (heaves syndrome).

Samples of mucus from the lower trachea were collected from 53 horses with chronic obstructive pulmonary disease and from 24 clinically normal horses. Serum samples were collected from 35 of the horses with chronic obstructive pulmonary disease and from the 24 normal horses. Samples were tested for inhibition of hemagglutination by influenza A equine 1 and 2 viruses. There were high levels of hemagglutination inhibiting activity against influenza A equine 1 in mucus samples from horses with chronic obstructive pulmonary disease.     

IgG antibody responses to an inhaled antigen in horses with "heaves" (recurrent airway obstruction).

A controlled experimental system for the evaluation of pulmonary immune responses in horses with "heaves" (recurrent airway obstruction) has been developed. We hypothesized that the humoral immune response to an inhaled antigen in diseased horses would be different from that of healthy horses and that chronic pulmonary inflammation would bias the production of IgG isotypes in diseased horses as compared to healthy horses. Healthy and affected horses were housed in a natural challenge environment (stabled, fed dusty hay) and exposed by inhalation, to a nebulized solution of keyhole limpet hemocyanin (KLH). Sera and bronchoalveolar lavage fluids (BALFs) were collected from horses prior to and following their inhalation exposure to the antigen. Differential cell counts were performed on the cells in the BALF. An enzyme-linked immunosorbent assay (ELISA) was used to determine the concentrations of IgGa, IgGb, IgG(T) and combined IgG specific for KLH in the sera and BALF. The percentages of neutrophils in the BALF of diseased horses were increased 4-6-fold over healthy horses. Combined IgG specific for KLH was significantly greater in BALF and serum from healthy compared to diseased horses. Differences in isotypes were also evident; however, only IgGb specific for KLH in the BALF was significantly increased in healthy versus diseased horses. Possible explanations for this difference include: (1) increased destruction of antigen before it could interact with lymphocytes, (2) down-regulation of IgGb production by inhibitory cytokines in diseased horses, or (3) binding of IgGb to Fc receptors on the large numbers of neutrophils in the lungs of diseased horses. In contrast to the prevailing notion that horses with heaves have exaggerated immune responses, our data suggest that diseased horses exposed to an aerosolized protein mount weaker IgG responses compared to healthy horses.     

Improvement of the lung function of horses with heaves by treatment with a botanical preparation for 14 days

The effects of an oral preparation containing a mixture of extracts from yellow gentian, garden sorrel, cowslip, verbena and common elder on the lung function of nine horses suffering from heaves were determined in a longitudinal crossover study. The horses were divided at random into a group of five (group 1) and a group of four (group 2). The horses in group 1 were each given 15 tablets of the preparation twice daily, while the horses in group 2 were left untreated. Fourteen days later, the horses in group 2 were given the same course of treatment while the horses in group 1 were left untreated. On being subjected to a histamine inhalation provocation test, five of eight horses tested appeared to be hyperresponsive to histamine. The treatment decreased the histamine sensitivity of three of them; it also caused a significant decrease in maximal intrapleural pressure difference of all the horses. The treatment had no significant effects on the clinical signs, the mucociliary activity or the cytology of the bronchoalveolar lavage fluid of the horses.     

Lack of clinical efficacy of a phosphodiesterase-4 inhibitor for treatment of heaves in horses

Phosphodiesterase-4 (PDE 4) enzyme inhibitors have been shown to have anti-inflammatory properties in various animal disease processes and therefore could be effective drugs for the treatment of equine airway diseases. The purpose of this study was to evaluate the efficacy and adverse effects of the PDE 4 inhibitor L-826,141 in horses with heaves. In a blinded parallel design, horses with heaves exposed daily to moldy hay were given a placebo for 14 days and then administered either L-826,141 (n = 6; loading dose of 1 mg/kg IV followed by 0.5 mg/kg IV q48h) or dexamethasone (n = 6; 0.04 mg/kg IV q24h) from days 15 to 29 (study 1). Pulmonary function and bronchoalveolar (BAL) cytology were evaluated weekly from baseline (day 0) to 29 days. In study 2, horses were treated with L-826,141 (1.0 mg/kg IV q24h) for 8 days. Although ex vivo lipopolysaccharide-induced tumor necrosis factor (TNF)-alpha and LTB4 production by fresh blood were inhibited up to 90% after repeated administrations of L-826,141, this treatment failed to improve lung function. In contrast, dexamethasone (positive control) treatment resulted in significant improvement in lung mechanics and airway function in all horses. Neither drug had a significant effect on BAL total cell counts and differential cytology. Administration of the PDE 4 inhibitor L-826,141 for up to 14 days to horses with heaves was not associated with an improvement in airway function or inflammation. These findings suggest that the PDE 4 enzyme is not a key mediator of lung inflammation in heaves.     

In vitro allergen-induced degranulation of pulmonary mast cells from horses with recurrent airway obstruction (heaves).

OBJECTIVE: To determine the capacity of pulmonary mast cells (PMC) to degranulate in response to various potential allergens and other secretagogues in horses with recurrent airway obstruction (heaves) and clinically normal horses before and after exposure to moldy hay. ANIMALS: 5 horses with heaves and 5 clinically normal horses. PROCEDURES: Heaves was characterized as an increased clinical respiratory score and maximum change in transpulmonary pressure of > 20 cm H2O after exposure. Bronchoalveolar lavage was performed during each period. Washed and resuspended cells were exposed for 20 minutes at 37 C with whole reconstituted freeze-dried preparations of Aspergillus fumigatus, Alternaria tenuis, and Ambrosia elatior, fungal extracts of Aspergillus fumigatus, Alternaria tenuis, and Micropolyspora faeni; A23187; and compound 48/80. Histamine release (HR) was used as a marker of degranulation. RESULTS: Compared with clinically normal horses, HR was significantly greater from PMC from horses with heaves during remission and exacerbation in response to whole preparations and extracts of Aspergillus fumigatus and whole preparations of Alternaria tenuis. Extracts of Alternaria tenuis caused significantly greater HR from PMC from horses with heaves during exacerbation. Histamine was also released from PMC in response to A23187 and to changes in osmolality of the medium, but only as a result of cell lysis by compound 48/80. CONCLUSIONS: Increased degranulation of PMC after antigenic challenge may contribute to the pathogenesis of heaves in horses. CLINICAL RELEVANCE: Strategies for prevention and treatment that attenuate degranulation of PMC may assist in the clinical management of horses with heaves.     

Malignant lymphoma in three horses with ulcerative pharyngitis

Three horses were examined for ulcerative pharyngitis, which had been unresponsive to treatment. Biopsy specimens of the pharyngeal lesions were characterized histologically by a mixed population of lymphocytes and histiocytes, suggesting chronic inflammation. Only when biopsy specimens of regional lymph nodes revealed this cell population disrupting the lymph node architecture was the diagnosis of malignant lymphoma made.     

Septic arthritis in adult horses

Septic arthritis in horses is a serious disease which can become life-threatening. In case the infection can be eliminated before irreversible joint damage occurs, complete recovery is possible. This article gives an overview of the literature concerning etiology, diagnosis and strategies of therapy in cases of septic arthritis in adult horses, with special reference to novel options of treatment.     

In vitro comparison of three fixation methods for humeral fracture repair in adult horses

The stiffness, load to failure, and bending moments of adult intact equine humeri and humeri repaired with 3 fixation techniques were determined in vitro. Bones were tested in axial compression (30 pairs), mediolateral 3-point bending (15 pairs), and caudocranial 3-point bending (15 pairs). An oblique osteotomy of 1 humerus of each pair was performed to simulate the long spiral oblique fractures that occur clinically in horses. Bones were repaired in 3 ways: group 1--nylon band cerclage fixation (20 bones); group 2--multiple intramedullary pinning (20 bones); and group 3--nylon band cerclage fixation and multiple intramedullary pinning (20 bones). Intact bones were significantly (P less than 0.05) stronger than repaired bones in each testing mode. Bones repaired with bands only were significantly less stiff in bending than were bones repaired with pins only or with pins and bands. In compression, only specimens repaired with pins and bands were significantly stiffer than were bones repaired with bands only. Bones repaired with bands only required significantly less load to failure in compression and in caudocranial bending than did bones repaired with pins only or with pins and bands. Bones repaired with pins only deformed through the full displacement of the actuator (5 cm), and pins deformed plastically. Bones repaired with pins and bands were stiffer and had higher bending moments than did bones repaired with pins only, but the differences were not significant.     

Avian mycobacteriosis in three horses

The clinical, bacteriologic and pathologic findings of three adult horses suffering from avian tuberculosis are presented. Chronic weight loss and hypoproteinemia were pertinent clinical abnormalities in all three horses. Gross pathologic lesions were characterized by chronic enterocolitis with mesenteric lymphadenopathy in two horses and hepatic granulomas in the third horse. The microscopic diagnoses were chronic, non-caseating granulomatous enterocolitis, and necrotizing, non-mineralizing granulomatous hepatitis, respectively. All three horses had granulomatous lymphadenitis of mesenteric lymph nodes with varying degrees of non-mineralizing, coagulation necrosis. Various serotypes of the Mycobacterium avium-intracellulare complex were isolated from selected tissues and feces.