Effect of different doses of inhaled ciclesonide on lung function, clinical signs related to airflow limitation and serum cortisol levels in horses with experimentally induced mild to severe airway obstruction.

BACKGROUND: Inhaled corticosteroids are effective for the treatment of equine asthma but they induce cortisol suppression with potential side effects. OBJECTIVES: To study the efficacy of ciclesonide, an inhaled corticosteroid with an improved safety profile, on lung function, clinical signs related to airway obstruction, and serum cortisol levels in asthmatic horses exposed to a mouldy hay challenge. STUDY DESIGN: Cross-over placebo controlled, blinded, randomised experiment. METHODS: Sixteen horses were enrolled in three subsequent dose-titration studies (8 horses/study) to investigate the effects of inhaled ciclesonide administered for 2 weeks at doses ranging from 450 to 2700 µg twice daily or 3712.5 µg once daily. Systemic dexamethasone (0.066 mg/kg per os) was our positive control. A placebo group was also studied. Lung function and clinical scores were blindly performed before and after 7 and 14 days of treatment. Serum cortisol was measured before and after 3, 5, 7, 10, 14 days of treatment as well as 3 and 7 days post treatment. RESULTS: After 7 days, dexamethasone induced a significant reduction in pulmonary resistance (from 2.5 ± 0.6 at day 0 to 1.1 ± 0.7 cm H2 O/L/s), pulmonary elastance (5.0 ± 2.6 to 1.2 ± 1.0 cm H2 O/L), and of the weighted clinical score (14.8 ± 4.7 to 8.0 ± 4.4). Similarly, ciclesonide 1687.5 µg twice daily significantly improved pulmonary resistance (2.7 ± 1.1 to 1.6 ± 0.8 cm H2 O/L/s), pulmonary elastance (5.2 ± 3.1 to 2.2 ± 1.3 cm H2 O/L), and weighted clinical score (13 ± 2.9 to 10.8 ± 4.2). Serum cortisol suppression (<50 nmol/L) systematically occurred with dexamethasone from day 3 of treatment up to day 3 post treatment, but not with ciclesonide at any tested doses. Placebo did not exert any significant beneficial effect. MAIN LIMITATIONS: Experimentally induced asthma exacerbations in horses might respond differently to treatment than naturally occurring exacerbations. CONCLUSIONS: Inhaled ciclesonide is an effective treatment for horses with equine asthma. Serum cortisol was unaffected by treatment.

Clinical findings and prognosis of interference injuries to the palmar aspect of the forelimbs in Standardbred racehorses: A study on 74 cases.

BACKGROUND: Information on interference injuries in racehorses is lacking. OBJECTIVE: To describe clinical findings and prognosis of palmar forelimb interference injuries in Standardbreds. STUDY DESIGN: Retrospective cohort study. METHODS: Records of 74 racehorses sustaining palmar forelimb interference injuries were studied; 7 occurred during training and 67 during racing. The number of starts before injury, hind shoeing status, gait penalties and racing speeds in cases occurring during racing were compared with negative controls (67 age, sex and speed category matched horses) from the same races. The number of starts and racing speed in 30 racing days preceding recruitment were compared with those following recruitment (negative controls) or return to racing (cases). Clinical aspects and outcome in interference-induced superficial digital flexor (SDF) tendonitis were compared with 77 horses with overstrain-induced SDF tendonitis. RESULTS: In 89% of cases, there was SDF tendonitis and this was associated with a longer time to return to racing (6 months vs. 1 months; P<0.001). The presence of gait penalties (odds ratio (OR) 11.13; 95% CI 3.74, 41.64; P<0.001) and unshod hind feet (OR = 6.26, 95% CI 2.26, 19.62; P<0.001) increased risk of interference injuries. After recruitment/return to racing, horses with interference injuries participated in a lower number of races (24 starts per racing day, interquartile range [IQR] 20-32) compared with controls (49, IQR 43-55, P<0.0001). Interference-induced tendonitis cases (n = 58) had a shorter time to return to racing (245 ± 137 days) than overstrain-induced tendonitis cases (331 ± 118 days, P<0.001). MAIN LIMITATIONS: Data were collected retrospectively; time of ultrasonographic assessment varied and health status of the racing controls is unknown. CONCLUSIONS: SDF tendonitis is common with palmar forelimb interference injuries in Standardbreds and increases time to return to racing. Interference-induced SDF tendonitis has a better prognosis than overstrain-induced tendonitis.

Bronchoalveolar lavage fluid neutrophilia is associated with the severity of pulmonary lesions during equine asthma exacerbations.

BACKGROUND: The severe form of equine asthma is associated with pathological changes of the peripheral airways and pulmonary parenchyma that are only partly described. Also, the relationship between these structural alterations and the percentage of neutrophils found within the airway lumen, assessed by bronchoalveolar lavage fluid (BALF) cytology, remains ill-defined. OBJECTIVE: To examine the histological lesions associated with equine asthma during disease exacerbation and remission, and their relationship with lung function and BALF neutrophilia. STUDY DESIGN: Observational retrospective study. METHODS: Peripheral lung tissues, BALF cytology and lung function data from 61 horses (22 controls, 24 asthma exacerbations and 15 asthma remission) were obtained from an equine pulmonary tissue bank. Two pathologists semi-quantitatively assessed histological features, including airway wall inflammation, interstitial fibrosis, mucus cell hyperplasia, mucostasis, peribronchiolar metaplasia, presence of granuloma and the overall severity of these lesions. RESULTS: Mucostasis, mucus cell hyperplasia, peribronchiolar metaplasia and interstitial fibrosis were associated with disease exacerbation (P≤0.05), and these changes were all attenuated during remission. Airway wall inflammation was greater in horses with asthma in exacerbation compared with horses with asthma in remission and control horses (P≤0.05). Acute (neutrophilic) airway wall inflammation was more frequently detected in asthmatic cases compared with control horses (P<0.0001) and was associated with BALF neutrophilia >5% in control horses (P = 0.002). The degree of bronchiolar inflammation was higher in asthmatic horses in remission stabled and treated pharmacologically compared with those kept on pasture (P = 0.04). MAIN LIMITATIONS: Samples obtained from a convenient cohort of horses were studied. CONCLUSIONS: Severely asthmatic horses present parenchymal and peribronchial/peribronchiolar lesions possibly contributing to the obstructive nature of the disease.

Age associated changes in peripheral airway smooth muscle mass of healthy horses.

Peripheral airway smooth muscle (ASM) mass is increased in severe equine asthma, but no information is available on age related changes in ASM. In this study, peripheral ASM dimensions were determined in healthy horses of different ages. The thickness of the peripheral ASM layer was constant in horses of different ages, but ASM occupied a greater proportion of the inner wall area in young horses compared to older horses. This finding suggests that equine airways experience a decrease in the relative abundance of ASM with age.

Development of a Semiquantitative Histological Score for the Diagnosis of Heaves Using Endobronchial Biopsy Specimens in Horses.

BACKGROUND: Remodeling of the peripheral airways persists during the asymptomatic phase of heaves. Assessing the histology of large bronchi could facilitate the diagnosis of heaves during remission of the disease. HYPOTHESIS: Airway inflammation and remodeling in endobronchial biopsy (EBB) specimens differentiate horses with heaves from controls, independently of their clinical status (exacerbation or remission). ANIMALS: Fourteen healthy horses and 24 horses with heaves. METHODS: A 14-point scoring system assessing central bronchial wall inflammation and remodeling was developed. The score was validated by 2 pathologists using specimens obtained from 18 horses (6 controls, 6 with heaves exacerbation, and 6 with heaves remission) in which lung function had been assessed with impulse oscillometry. Clinical and research application of the score was evaluated using biopsy specimens obtained from 20 additional horses (8 controls, 6 with heaves exacerbation, and 6 with heaves remission). RESULTS: The score was repeatable (interclass correlation coefficient = 69%). It differentiated horses with heaves in exacerbation (mean ± SD: 6.2 ± 2.2) from those in remission (4.0 ± 1.0) and controls (3.6 ± 1.7, P < 0.0001). The histological scores of horses with heaves correlated with the ratio of respiratory resistance (R) at 5 and 10 Hz (R5 : R10 ratio, r = 0.65, P = 0.03), a parameter assessing airway obstruction. CONCLUSIONS AND CLINICAL SIGNIFICANCE: The proposed histological scoring system correlates with the degree of airway obstruction measured by impulse oscillometry. However, it does not discriminate horses with heaves in remission from controls. Evaluation of EBB specimens might be considered in future research and clinical studies of respiratory diseases in horses.

Endoscopic Evaluation of Angiogenesis in the Large Airways of Horses with Heaves Using Narrow Band Imaging.

BACKGROUND: Heaves is a severe debilitating condition of horses, characterized by lower airway inflammation and permanent structural changes of the bronchial wall. Chronic inflammation promotes the formation of new vessels, a phenomenon known as angiogenesis. Narrow band imaging (NBI) endoscopy is a noninvasive technique that enhances the visualization of submucosal vessels, and commonly is employed for the study of angiogenesis in human patients. OBJECTIVES: Using NBI, we aimed to determine whether or not the central airways of horses with heaves undergo angiogenesis. ANIMALS: Horses with heaves during exacerbation of the disease (n = 5) and healthy controls (n = 6). METHODS: A library of NBI images was established from previously recorded videoendoscopies. Images were acquired by an operator blinded to horse ID. Images were obtained from 3 sites: 130 from the trachea (14 ± 9.3 [mean ± SD] images per horse with heaves and 10 ± 5.4 from controls; P = .45), 58 from the carina (5.4 ± 3.2 from horses with heaves and 5.2 ± 2.8 fromn controls; P > .99) and 167 from the intermediate bronchi (17.8 ± 6.7 from horses with heaves and 13 ± 5.6 from controls; P = .17). Using dedicated stereology software (NewCAST, Visiopharm; Denmark), the volume density of superficial and deep vessels was calculated blindly by point counting at each site for all horses. RESULTS: In the trachea, the volume density of superficial vessels was increased in horses with heaves compared to controls (P = .02). No difference was found between groups for the volume density of both superficial and deep vessels at the carina or intermediate bronchi. CONCLUSION AND CLINICAL RELEVANCE: NBI imaging of the airways was easily performed in standing sedated horses.

Environmental heat and airborne pollen concentration are associated with increased asthma severity in horses.

REASON FOR PERFORMING STUDY: Clinical exacerbations of severe equine asthma (formerly recurrent airway obstruction [RAO]) are more frequently reported during winter when horses are exposed to airborne dusts during stabling. However, we have also observed a worsening of clinical signs on days during a heatwave. OBJECTIVES: To investigate the association between environmental temperature and humidity and clinical signs of asthma in horses during clinical exacerbation of the disease. STUDY DESIGN: Retrospective longitudinal study. METHODS: Historical data on 14 severe asthmatic horses exposed to a dusty environment and evaluated using a previously validated clinical scoring system were analysed. Barn temperature and relative humidity values were obtained and air enthalpy (h) calculated. Correlation tests were used to study the relationship between mean daily clinical scores of horses and environmental variables. Lung function parameters recorded at 4 day intervals during hot (25°C) and warm (18°C) barn conditions were compared using a paired t test. RESULTS: Significant positive correlations were observed between the mean daily clinical score and temperature (r = 0.58, P = 0.01) and air enthalpy (r = 0.55, P = 0.02). Maximal daily temperature correlated with airborne pollen concentrations (r = 0.51, P = 0.0002). In the absence of changes in the management of horses, higher barn temperature and enthalpy were associated with increased transpulmonary pressure (P = 0.005), pulmonary resistance (P = 0.008) and elastance values (P = 0.005). CONCLUSIONS: Providing a cold environment may help attenuate the severity of airway obstruction in uncontrolled exacerbations of severe equine asthma. Furthermore, variations in environmental heat and associated pollen concentrations should also be taken into account when evaluating the response to therapy in clinical or research settings.

Serum Surfactant Protein D and Haptoglobin as Potential Biomarkers for Inflammatory Airway Disease in Horses.

BACKGROUND: The identification of serum biomarkers of lung inflammation would facilitate the diagnosis of inflammatory airway disease (IAD) in horses. HYPOTHESIS: Horses with IAD have higher serum concentrations of markers of inflammation compared to controls. ANIMALS: Twelve horses with IAD and 10 control horses. METHODS: This was a prospective case-control study. Blood and BALF were collected from horses with IAD and controls. Serum concentration of surfactant protein D (SP-D), haptoglobin, serum amyloid A (SAA) and of the soluble form of triggering receptor expressed on myeloid cells 1 (sTREM-1) was measured using commercial ELISA tests. RESULTS: Horses with IAD had higher serum concentration (log-transformed values) of SP-D (mean ± SD: 1.773 ± 0.51), haptoglobin (6.657 ± 0.202) and SAA (0.128 ± 0.396) compared to controls (0.942 ± 0.226, 6.38 ± 0.22, -0.398 ± 0.319, respectively; P < .01 for all). Furthermore, the concentrations of SP-D and haptoglobin combined allowed differentiating the 2 groups (IAD: 8.43 ± 0.564, controls: 7.322 ± 0.249, P < .0001) with a sensitivity and specificity of 100% when a cut-off of 7.70 (log value) was employed. CONCLUSIONS AND CLINICAL IMPORTANCE: Surfactant protein D and haptoglobin serum concentrations could be a diagnostic aid in IAD. Further studies are necessary to establish the specificity of our findings before they can be applied in everyday practice.

PI3K and MAPKs regulate neutrophil migration toward the airways in heaves.

BACKGROUND: Neutrophils accumulate in the airways of horses with heaves. They likely play an important role in the disease pathogenesis. Understanding the pathways regulating their migration may help identifying new therapeutic targets. HYPOTHESIS: MAPK and PI3K pathways are involved in neutrophil migration toward the airway lumen in heaves. ANIMALS: Twelve heaves-affected horses and 4 healthy horses. METHODS: Migratory activity of bronchoalveolar lavage fluids (BALF) from horses with heaves and healthy horses was compared by means of a Boyden chamber. Involvement of MAPK and PI3K pathways in neutrophil migration was investigated by pretreating neutrophils with inhibitors of p38 MAPK, JNK, MEK1/2, and PI3K. The capacity of a p38 MAPK inhibitor at decreasing neutrophil chemotaxis toward the airways was also evaluated in vivo. RESULTS: BALF from symptomatic heaves-affected horses induced a greater degree of chemokinesis (P = .0004) than BALF from healthy horses. Although all pathways tested were involved in neutrophil migration, inhibition of PI3K was most potent in vitro. An inhibitor of p38 MAPK administered before challenge in horses with heaves did not alter BALF chemokinetic properties. BALF neutrophil percentage and BALF migratory activity were positively correlated after 14 and 35 days of antigen challenge in healthy (P = .05; R(2) = 0.82) and heaves-affected horses (P = .03; R(2) = 0.76), respectively. CONCLUSIONS AND CLINICAL IMPORTANCE: MAPK and PI3K pathways regulate neutrophil migration induced by BALF of horses with heaves. Inhibition of multiple pathways might be required to completely abolish BALF-induced neutrophil migratory activity and possibly inflammation in heaves.