Equine pulmonary disease: a case control study of 300 referred cases. Part 2: Details of animals and of historical and clinical findings

Effects of soaked hay on lung function and airway inflammation in horses with severe asthma

BACKGROUND

Reducing inhaled dust particles improves lung function in horses with severe asthma. Soaked hay is commonly used by owners, but its efficacy in improving lung function and inflammation has not been documented.

OBJECTIVES

To measure the effects of soaked hay and alfalfa pellets in horses with severe asthma.

ANIMALS

Ten adult horses with severe asthma from a research colony.

METHODS

Prospective controlled trial. Horses in clinical exacerbation were housed indoors and allocated to be fed either soaked hay (n = 5) or alfalfa pellets (n = 5) for 6 weeks. Soaked hay was immersed for 45 minutes and dried out hay was discarded between meals. Pulmonary function and clinical scores were measured before and after 2, 4, and 6 weeks. Tracheal mucus scores and bronchoalveolar lavages were performed before and after 6 weeks. Lung function was analyzed with a linear mixed model using log-transformed data.

RESULTS

Lung resistance decreased from (median (range)) 2.47 (1.54-3.95) to 1.59 (0.52-2.10) cmH2 O/L/s in the pellets group and from 1.89 (1.2-3.54) to 0.61 (0.42-2.08) cmH2 O/L/s in the soaked hay group over the 6-week period for an average difference of 1.06 cmH2 O/L/s for pellets (95% confidence interval [95% CI]: 0.09-2.04, P = .03, not significant after correction) and 1.31 cmH2 O/L/s for soaked hay (95% CI: -0.23 to 2.85, P < .001, significant).

CONCLUSION AND CLINICAL IMPORTANCE

Soaked hay can control airway obstruction in horses with severe asthma. The strict protocol for soaking and discarding dried-out hay in this study could however be considered too great of an inconvenience by owners.

Decision Making in Severe Equine Asthma-Diagnosis and Monitoring

Decision making consists of gathering quality data in order to correctly assess a situation and determine the best course of action. This process is a fundamental part of medicine and is what enables practitioners to accurately diagnose diseases and select appropriate treatment protocols. Despite severe equine asthma (SEA) being a highly prevalent lower respiratory disease amongst equids, clinicians still struggle with the optimization of routine diagnostic procedures. The use of several ancillary diagnostic tests has been reported for disease identification and monitoring, but many are only suitable for research purposes or lack practicality for everyday use. The aim of this paper is to assist the equine veterinarian in the process of decision making associated with managing SEA-affected patients. This review will focus on disease diagnosis and monitoring, while also presenting a flow-chart which includes the basic data that the clinician must obtain in order to accurately identify severely asthmatic horses in their everyday routine practice. It is important to note that European and American board-certified specialists on equine internal medicine can provide assistance in the diagnosis and treatment plan of SEA-affected horses.

Pathology, infectious agents and horse- and management-level risk factors associated with signs of respiratory disease in Ethiopian working horses

BACKGROUND

Respiratory disease is a common cause for presentation of working horses to clinics in Ethiopia and a priority concern for owners.

OBJECTIVES

To identify risk factors for and association of pathogens with respiratory signs in working horses.

STUDY DESIGN

Unmatched case-control study.

METHODS

Cases were those animals recently coughing (last 7 days) or observed with coughing, nasal discharge or altered respiration at the time of examination. A physical exam and respiratory endoscopy were performed including a tracheal wash sample to detect the presence of pathogens and serology performed on blood. An owner questionnaire was administered. Risk factors were determined using multivariable logistic regression.

RESULTS

Data on 108 cases and 93 unmatched control horses were obtained. Case horses often had underlying lower airway pathology and were significantly more likely to have Streptococcus zooepidemicus detected (OR: 12.4, 95% CI: 3.6-42.4). There was no evidence of a major role for viral respiratory pathogens. Risk factors included completion of strenuous work (OR: 2.7, 95% CI: 1.2-6.3), drinking from stagnant water sources (OR: 2.3, 95% CI: 1.0-5.2) or being housed on a cobbled floor (OR: 2.0, 95% CI: 1.1-3.8). There were increased odds of respiratory disease in young and old horses in this population.

MAIN LIMITATIONS

Samples for pathogen detection and cytology were only taken from the trachea.

CONCLUSION

S. zooepidemicus, a common commensal, may play a role in clinical respiratory disease in this population.

Equine Asthma: Current Understanding and Future Directions

The 2019 Havemeyer Workshop brought together researchers and clinicians to discuss the latest information on Equine Asthma and provide future research directions. Current clinical and molecular asthma phenotypes and endotypes in humans were discussed and compared to asthma phenotypes in horses. The role of infectious and non-infectious causes of equine asthma, genetic factors and proposed disease pathophysiology were reviewed. Diagnostic limitations were evident by the limited number of tests and biomarkers available to field practitioners. The participants emphasized the need for more accessible, standardized diagnostics that would help identify specific phenotypes and endotypes in order to create more targeted treatments or management strategies. One important outcome of the workshop was the creation of the Equine Asthma Group that will facilitate communication between veterinary practice and research communities through published and easily accessible guidelines and foster research collaboration.

Immunomodulatory asthma therapy in the equine animal model: A dose-response study and evaluation of a long-term effect

INTRODUCTION

Equine asthma represents a naturally occurring animal model for human allergic neutrophilic asthma. Inhalative nanoparticle-bound cytosine-phosphate-guanosine (CpG-GNP) immunotherapy, independent of specific allergens, has already shown promising clinical and immunological results in previous studies and offers the possibility to treat the underlying cause of the disease. This study analyses the relationship between dose and response, and evaluates a possible long-term effect.

METHODS

In the prospective, randomised, double-blind clinical field study, 29 horses suffering from equine asthma received 10 inhalation treatments with either 187.5 µg CpG-GNP (CpG single dose [CpGsd]; n = 11), 375 µg CpG-GNP double dose (CpG double dose [CpGdd]; n = 9) (q48h for 20 days) or 1600 µg beclomethasone (n = 9) (q24h for 10 days). Each horse was examined three times: before the treatment (I), immediately after the 10 inhalations (II), and 8 weeks after the final inhalation (III). The three groups were compared according to clinical and laboratory parameters. The study examined the sustainability of the long-term effect of the treatment after 8 weeks, as well as the tolerability of the formula as a double dose.

RESULTS

The CpGsd resulted in a significant improvement in 82% of the parameters, the CpGdd in 72%. In the long-term evaluation, the CpGsd showed a significant improvement in 100% of the parameters in comparison to the initial values, the CpGdd in 67%. On the immunological level, the bronchoalveolar lavage revealed a significant reduction of IL-4, IL-8, and interferon-γ.

CONCLUSION

Both CpG groups displayed significant improvements in clinical and laboratory parameters, especially regarding the long-term effect of CpGsd. Doubling the CpG dose did not result in any improvement in comparison to the original single dose. On the immunological level, an anti-inflammatory, as well as an immunomodulatory effect, apart from a Th2-dominated immune response, could be observed. This immunomodulatory inhalation treatment could indicate a new possibility for human allergic asthma therapy.

Association between inflammatory airway disease of horses and exposure to respiratory viruses: a case control study

Background

Inflammatory airway disease (IAD) in horses, similar to asthma in humans, is a common cause of chronic poor respiratory health and exercise intolerance due to airway inflammation and exaggerated airway constrictive responses. Human rhinovirus is an important trigger for the development of asthma; a similar role for viral respiratory disease in equine IAD has not been established yet.

Methods

In a case–control study, horses with IAD (n = 24) were compared to control animals from comparable stabling environments (n = 14). Horses were classified using pulmonary function testing and bronchoalveolar lavage. PCR for equine rhinitis virus A and B (ERAV, ERBV), influenza virus (EIV), and herpesviruses 2, 4, and 5 (EHV-2, EHV-4, EHV-5) was performed on nasal swab, buffy coat from whole blood, and cells from BAL fluid (BALF), and serology were performed. Categorical variables were compared between IAD and control using Fisher’s exact test; continuous variables were compared with an independent t-test. For all analyses, a value of P <0.05 was considered significant.

Results

There was a significant association between diagnosis of IAD and history of cough (P = 0.001) and exercise intolerance (P = 0.003) but not between nasal discharge and IAD. Horses with IAD were significantly more likely to have a positive titer to ERAV (68 %) vs. control horses (32 %). Horses with IAD had higher log-transformed titers to ERAV than did controls (2.28 ± 0.18 v.1.50 ± 0.25, P = 0.038). There was a significant association between nasal shedding (positive PCR) of EHV-2 and diagnosis of IAD (P = 0.002).

Conclusions

IAD remains a persistent problem in the equine population and has strong similarities to the human disease, asthma, for which viral infection is an important trigger. The association between viral respiratory infection and development or exacerbation of IAD in this study suggests that viral infection may contribute to IAD susceptibility; there is, therefore, merit in further investigation into the relationship between respiratory virus exposure and development of IAD.

Evaluation of coughing and nasal discharge as early indicators for an increased risk to develop equine recurrent airway obstruction (RAO)

Background

It is often assumed that horses with mild respiratory clinical signs, such as mucous nasal discharge and occasional coughing, have an increased risk of developing recurrent airway obstruction (RAO).

Hypothesis

Compared to horses without any clinical signs of respiratory disease, those with occasional coughing, mucous nasal discharge, or both have an increased risk of developing signs of RAO (frequent coughing, increased breathing effort, exercise intolerance, or a combination of these) as characterized by the Horse Owner Assessed Respiratory Signs Index (HOARSI 1–4).

Animals

Two half‐sibling families descending from 2 RAO‐affected stallions (n = 65 and n = 47) and an independent replication population of unrelated horses (n = 88).

Methods

In a retrospective cohort study, standardized information on occurrence and frequency of coughing, mucous nasal discharge, poor performance, and abnormal breathing effort—and these factors combined in the HOARSI—as well as management factors were collected at intervals of 1.3–5 years.

Results

Compared to horses without clinical signs of respiratory disease (half‐siblings 7%; unrelated horses 3%), those with mild respiratory signs developed clinical signs of RAO more frequently: half‐siblings with mucous nasal discharge 35% (P < .001, OR: 7.0, sensitivity: 62%, specificity: 81%), with mucous nasal discharge and occasional coughing 43% (P < .001, OR: 9.9, sensitivity: 55%, specificity: 89%); unrelated horses with occasional coughing: 25% (P = .006, OR = 9.7, sensitivity: 75%, specificity: 76%).

Conclusions and Clinical importance

Occasional coughing and mucous nasal discharge might represent an increased risk of developing RAO.

Qualitative and quantitative evaluation of equine respiratory mechanics by impulse oscillometry

REASONS FOR PERFORMING STUDY

The long-established conventional reference technique (CRT) for measuring respiratory mechanics in horses lacks sensitivity and there is a need for further refinement in new technology, such as the impulse oscillometry system (IOS).

OBJECTIVES

To evaluate the potential use of the IOS as a clinical respiratory function test and compare it to the current CRT in horses suffering from common upper and lower airway dysfunctions.

METHODS

Six healthy horses were tested before and after induction of a unilateral nasal obstruction (UNO) or transient left laryngeal hemiplegia (LLH). Six heaves-affected horses were tested in clinical remission and during a heaves crisis, before and after nebulisation of cumulative doses of a bronchodilator therapy (ipratropium bromide; IPB).

RESULTS

As opposed to the CRT, the IOS was able to detect partial upper airway obstruction (UAO) caused by UNO or LLH in resting horses, without differentiating both conditions. Upper airway obstruction caused an upward shift of resistance (R(rs)) from 5 to 35 Hz without altering reactance (X(rs)). As for the CRT, IOS respiratory parameters measured in heaves-affected horses in crisis differed significantly from values measured during remission. The difference in frequency-dependent behaviour of R(rs) and X(rs) allowed discrimination between upper and lower airway obstructions. Bronchodilator treatment induced significant dose-dependent changes in X(rs) at 5 and 10 Hz, from the first dose. Total pulmonary resistance (RL) and R(rs) at 5 Hz were affected from the second dose and displayed similar sensitivity. Although post treatment RL values were comparable to remission, R(rs) and X(rs) remained significantly different, characterising persistent peripheral obstruction.

CONCLUSIONS

The IOS was more sensitive than the CRT in detecting partial UAO in resting horses and persistent post treatment peripheral dysfunction in heaves-affected horses. The IOS is a sensitive test that provides graded quantitative and qualitative information on disease-induced respiratory dysfunctions as well as on treatment efficiency in horses.

POTENTIAL RELEVANCE

The IOS could represent a practical and sensitive alternative respiratory function test for routine clinical investigations of common airway obstructive diseases and therapy in horses.

Mixed inheritance of equine recurrent airway obstruction

BACKGROUND

Mode of inheritance of equine recurrent airway obstruction (RAO) is unknown.

HYPOTHESIS

Major genes are responsible for RAO.

ANIMALS

Direct offspring of 2 RAO-affected Warmblood stallions (n = 197; n = 163) and a representative sample of Swiss Warmbloods (n = 401).

METHODS

One environmental and 4 genetic models (general, mixed inheritance, major gene, and polygene) were tested for Horse Owner Assessed Respiratory Signs Index (1-4, unaffected to severely affected) by segregation analyses of the 2 half-sib sire families, both combined and separately, using prevalences estimated in a representative sample.

RESULTS

In all data sets the mixed inheritance model was most likely to explain the pattern of inheritance. In all 3 datasets the mixed inheritance model did not differ significantly from the general model (P= .62, P= 1.00, and P= .27) but was always better than the major gene model (P < .01) and the polygene model (P < .01). The frequency of the deleterious allele differed considerably between the 2 sire families (P= .23 and P= .06). In both sire families the displacement was large (t= 17.52 and t= 12.24) and the heritability extremely large (h(2)= 1).

CONCLUSIONS AND CLINICAL RELEVANCE

Segregation analyses clearly reveal the presence of a major gene playing a role in RAO. In 1 family, the mode of inheritance was autosomal dominant, whereas in the other family it was autosomal recessive. Although the expression of RAO is influenced by exposure to hay, these findings suggest a strong, complex genetic background for RAO.

Exhaled breath condensate hydrogen peroxide and pH for the assessment of lower airway inflammation in the horse

Measurement of hydrogen peroxide (H(2)O(2)) concentration and pH in exhaled breath condensate (EBC) is useful for detection and monitoring of asthma in humans. In contrast, limited information on the use of these parameters for the investigation of lower airway inflammation (LAI) is available for horses. Aims of the current study were to investigate the intra- and inter-day variations of EBC H(2)O(2) concentration and pH in horses and establish any relationship(s) with LAI. Both intra- and inter-day variability of EBC H(2)O(2) concentration were large, while those of pH were small. No significant difference in the intra-day or inter-day H(2)O(2) concentrations or pH measurements were found in control or LAI horses, except for inter-day H(2)O(2) concentration in horses with LAI (p=0.019). There was no significant difference in EBC pH or H(2)O(2) concentration between control and LAI horses, however a trend for a reduced pH in horses with LAI was observed.

Respirable dust concentrations in equine stables. Part 2: The benefits of soaking hay and optimising the environment in a neighbouring stable

The effect of soaking hay to minimise equine breathing zone respirable dust concentration (RDC) is unknown, as is the duration of soaking required. Additionally, the influence of the bedding and forage used in one stable on the mean and maximum RDC in a neighbouring stable within a common airspace is unknown. Consequently, in the management of equine environmental respiratory disease uncertainty remains about the necessity for optimising conditions in neighbouring stables. Investigations using a real-time continuous particle monitor revealed that when feeding hay, horses' mean breathing zone RDC was significantly reduced if the hay was immersed or soaked for a prolonged time, prior to feeding. There was no advantage in soaking for an extended time period. Implementing management changes in one stable (changing from straw bedding and hay feeding to wood shavings bedding and haylage feeding) significantly reduced mean and maximum background RDC in a neighbouring stable within a common airspace.

A survey of horse owners in Great Britain regarding horses in their care. Part 2: Risk factors for recurrent airway obstruction

REASONS FOR PERFORMING STUDY

Recurrent airway obstruction (RAO) is a commonly encountered respiratory condition of horses. Despite this, the epidemiology of this predominately manageable and reversible disease in Great Britain has been largely ignored.

OBJECTIVES

To estimate the prevalence of RAO in the general horse population of Great Britain and to investigate possible risk factors for RAO associated with management or early life.

METHODS

Horse owners were surveyed using a self-administered postal questionnaire that contained a risk-screening questionnaire (RSQ) designed to identify horses with RAO. These owners were randomly selected, following geographical stratification, using 2-stage cluster sampling of veterinary practices and their clients. Multilevel, multivariable logistic regression models were used to investigate risk factors for RAO in the selected horse population.

RESULTS

The estimated true prevalence of RAO in the selected horse population was 14.0% (95%CI 10.7-17.4%). Risk factors for RAO identified in a general horse management logistic regression model included increasing age and exposure to an urbanised environment. Recurrent airway obstruction has long been associated with mature horses while the association with an urbanised environment could be related to different management practices in these areas or possibly air pollution could be involved. The second model associated exposure to hay and respiratory infection in early life with a horse having RAO in later life. Challenges to the respiratory system in early life may be involved in the development of this disease.

CONCLUSIONS AND POTENTIAL RELEVANCE

Recurrent airway obstruction is a significant health problem in the horse population of Great Britain. This form of epidemiological investigation highlights potential risk factors for the disease.

Temporal regulation of cytokine mRNA expression in equine recurrent airway obstruction

Acute and chronic inflammation of the airway remains an important health problem for equids. "Heaves" or recurrent airway obstruction (RAO) remains one of the most commonly diagnosed conditions affecting the lung of older horses in Europe and the United States. The typical clinical signs of RAO include non-productive coughing, serous nasal discharge, labored expiratory effort, and flaring of the nostrils. Auscultation of the lungs of the affected horse often reveals abnormal respiratory sounds, described as crackles and wheezes, throughout the area of the lung field. These clinical signs occur secondary to an inflammatory response that results in bronchospasm, excessive mucus production and airway obstruction. This inflammatory response is characterized by the presence of excessive mucus and inflammatory cells, primarily neutrophils, in the small airways. Most evidence suggests that RAO is the result of a pulmonary hypersensitivity to inhaled antigens. Exposure of affected horses to hay dust, pollens, and mold spores leads to neutrophil accumulation in the lung and bronchospasm. The identification of allergen-specific IgE in bronchoalveolar lavage (BAL) fluid and sera of affected horses supports the involvement of a late phase, IgE-mediated, hypersensitivity reaction in the pathogenesis of equine RAO. The production of IgE antibodies is regulated by the cytokines IL-4 and IL-13. Using a quantitative PCR method we have reported that horses with RAO exhibit a modified Type 2 cytokine response characterized by the production of IL-4 and IL-13 mRNA, but not IL-5 mRNA in BAL cells. Interferon-gamma mRNA was also elevated, suggesting a mixed response. While these results are consistent with equine RAO being the result of an aberrant Type 2 cytokine response to inhaled allergens, others have failed to find any evidence of elevated Type 2 cytokine mRNA in BAL from horses with "heaves". It is likely that these disparate results could be the result of differences in the clinical stage of the affected animals or the timing of sample collection. Here, we report a diverse pattern of cytokine gene expression when sampling a group of affected horses over a period of time.

Climatic and aeroallergen risk factors for chronic obstructive pulmonary disease in horses

OBJECTIVE

To estimate the association between climate and airborne pollen and fungal factors and chronic obstructive pulmonary disease (COPD) in horses.

SAMPLE POPULATION

Data from 1,444 horses with a diagnosis of COPD.

PROCEDURE

The Veterinary Medical Database was used to identify records of horses admitted to veterinary teaching hospitals in the United States and Canada between 1990 and 1999. Rainfall, mean minimum and maximum temperature, and maximum monthly pollen and fungal spore (mold) counts recorded at the city closest to where the hospital is located were identified for each month data were reported to the Veterinary Medical Database. Associations between climatic and aeroallergen data and monthly prevalence of COPD were estimated by use of cross-correlation and logistic regression models.

RESULTS

Significant positive correlations were found between prevalence of COPD and rainfall 3 months previously, minimum temperature 1 and 2 months previously, total pollen counts measured 3 months previously, and total mold counts measured during the same month and 1 month previously.

CONCLUSIONS AND CLINICAL RELEVANCE

Outdoor aeroallergens and climatic factors may contribute to the occurrence of COPD in horses.

Inflammatory airway disease, nasal discharge and respiratory infections in young British racehorses

REASONS FOR PERFORMING STUDY

Respiratory disease is important in young Thoroughbred racehorses, but the variation in the rates of occurrence between different ages and training groups has not been characterised.

OBJECTIVES

To determine the rates of respiratory disease, particularly inflammatory airway disease (IAD), as well as evidence of infection, and their variation between age and group.

METHODS

Horses were examined monthly in 7 British flat training yards over a 3 year period. IAD was defined as increased mucus in the trachea with increased proportions of neutrophils in tracheal wash samples. Frequencies of disease outcomes were estimated from the data.

RESULTS

The prevalence of IAD was 13.8% and the incidence was 8.9 cases/100 horses/month. Rates varied with training and age groups, decreasing in older animals. The prevalence of nasal discharge (ND) was 4.1%. Rates of bacterial isolation were more common than viral infections. The incidence and prevalence of several bacterial species decreased with age.

CONCLUSIONS

IAD and ND were common in young racehorses, varying significantly between training groups and decreasing with age, consistent with infection playing a role in aetiology.

POTENTIAL RELEVANCE

The high prevalence of IAD in 2-year-old horses in Britain suggests that routine endoscopic examination may be helpful in providing early diagnosis and appropriate therapy. The transmission of bacteria and viruses within and between groups of young animals and the role of infection, stable environment and factors inherent to each horse, including their genetic make-up, in the multifactorial aetiology of the disease all merit further study.

Association between respiratory disease and bacterial and viral infections in British racehorses

Respiratory disease is important in horses, particularly in young Thoroughbred racehorses, and inflammation that is detected in the trachea and bronchi (termed inflammatory airway disease [IAD]) is more significant in this population in terms of impact and frequency than other presentations of respiratory disease. IAD, which is characterized by neutrophilic inflammation, mild clinical signs, and accumulation of mucus in the trachea, may be multifactorial, possibly involving infections and environmental and immunological factors, and its etiology remains unclear. This 3-year longitudinal study of young Thoroughbred racehorses was undertaken to characterize the associations of IAD and nasal discharge with viral and bacterial infections. IAD was statistically associated with tracheal infection with Streptococcus pneumoniae (capsule type 3), Streptococcus zooepidemicus, Actinobacillus spp., and Mycoplasma equirhinis and equine herpesvirus 1 and 4 infections, after adjustment for variation between training yards, seasons, and age groups. The association with S. pneumoniae and S. zooepidemicus was independent of prior viral infection and, critically, was dependent on the numbers of organisms isolated. S. pneumoniae was significant only in horses that were 2 years old or younger. The prevalence and incidence of IAD, S. zooepidemicus, and S. pneumoniae decreased in parallel with age, consistent with increased disease resistance, perhaps by the acquisition of immunity. The study provided evidence for S. zooepidemicus and S. pneumoniae playing an important etiological role in the pathogenesis of IAD in young horses.

Analysis of risk factors for recurrent airway obstruction in North American horses: 1,444 cases (1990-1999)

OBJECTIVE

To identify risk factors for recurrent airway obstruction (RAO) among horses examined at veterinary teaching hospitals in North America.

DESIGN

Retrospective case-control study.

ANIMALS

1,444 horses with RAO and 1,444 control horses examined for other reasons.

PROCEDURE

The Veterinary Medical Database was searched for records of horses in which RAO was diagnosed. A control group was identified by randomly selecting a horse with a diagnosis other than RAO that matched the institution and year of admission for each of the horses with RAO. Information obtained included hospital, admission year and month, age, sex, breed, and discharge status. The association between risk factors and diagnosis of RAO was estimated with logistic regression models.

RESULTS

The risk of RAO increased significantly with age, with horses > or = 7 years old being 6 to 7 times as likely to have RAO as were horses < or = 4 years old. Thoroughbreds were 3 times as likely to have RAO as were ponies. Horses were 1.6 and 1.5 times as likely to be examined because of RAO during winter and spring, respectively, than they were during summer.

CONCLUSIONS AND CLINICAL RELEVANCE

Results suggest that RAO was more likely to be diagnosed in females, horses > or = 4 years old, and Thoroughbreds and that RAO has a seasonal distribution.

Efficacy of montelukast in the treatment of chronic obstructive pulmonary disease in five horses

Five horses with moderate to severe chronic obstructive pulmonary disease (COPD) were treated with 0.11 (0.01) mg/kg bodyweight of montelukast, a cysteinyl leukotriene receptor antagonist, once a day for 26 days. The horses were evaluated clinically and endoscopically and subjected to arterial blood gas analysis and lung function tests before and after the period of treatment, and the plasma concentrations of montelukast were determined by high-performance liquid chromatography with fluorescence detection. The treatment did not result in statistically significant differences in the total scores of clinical and endoscopical signs, or in the difference in the arterioalveolar partial pressure of oxygen, maximal changes in pleural pressure, pulmonary resistance or dynamic compliance. The mean (sd) peak plasma concentration (C(max0) of montelukast was 12 (4) ng/ml and was reached 66 (13) minutes (t(max)) after its oral administration. The dose of montelukast per kg bodyweight was approximately the same as that for human beings, but the C(max) in the horses was 28 times lower and the t(max) was reached in one-fifth of the time, suggesting that its oral bioavailability may be lower.

Equine recurrent airway obstruction: pathogenesis, diagnosis, and patient management

Recurrent airway obstruction is a condition that affects some older horses maintained in confinement. Clinical signs range from exercise intolerance with occasional cough to dyspnea at rest. Bronchoalveolar lavage cytology is characterized by neutrophilic leukocytosis (15%-85%) and is recommended for making the diagnosis in horses with mild to moderate disease. Environmental management combined with periodic bronchodilator and antiinflammatory corticosteroid therapy yields the best prognosis for disease remission.

A long-term study of 277 cases of equine sinonasal disease. Part 1: details of horses, historical, clinical and ancillary diagnostic findings

The clinical and ancillary diagnostic findings in equine sinnasal disease were studied. The diagnoses in 277 referred (1984-1996) cases of equine sinonasal disease included the following (% all cases): 67 cases (24.2%) primary sinusitis, 61 (22.0%) dental sinusitis, 37 (13.4%) sinus cysts, 22 (7.9%) sinonasal neoplasia, 21 (7.6%) progressive ethmoid haematoma, 17 (6.1%) sinonasal trauma, 13 (4.7%) sinonasal mycosis, 11 (4.0%) rostral maxillary cheek tooth infection, 7 (2.5%) sinonasal polyps, 7 (2.5%) cases of nasal epidermal inclusion cysts and 14 (5.1%) miscellaneous sinonasal disorders. Many disorders showed similar clinical signs including nasal discharge (present in 88% of all cases) and facial swelling (46%). Most disorders were chronic, with a median duration of signs of 12 weeks (range 3 days- 6 years) prior to referral. Sinus cysts and sinonasal neoplasia were significantly (P<0.05) more frequently associated with gross distortion of the nasal passages and facial bones than the other sinonasal disorders. Endoscopic changes were detected per nasum in 91% of cases, but contributed to the exact diagnosis in only 20%. Radiography revealed abnormalities in 81% of cases but was diagnostically useful in only 36%. Sinoscopy was diagnostically useful in 70% of the 61 cases where used.

Clinical signs, evaluation of bronchoalveolar lavage fluid, and assessment of pulmonary function in horses with inflammatory respiratory disease

OBJECTIVE

To evaluate the association among clinical signs, results of cytologic evaluation of bronchoalveolar lavage (BAL) fluid, and measures of pulmonary function in horses with inflammatory respiratory disease.

ANIMALS

9 healthy horses, 5 horses with inflammatory airway disease (IAD), and 9 horses with chronic obstructive pulmonary disease (COPD).

PROCEDURES

Clinical examination, lung function tests, and BAL were performed on each horse.

RESULTS

Standard lung mechanics of horses with exacerbated COPD differed significantly from those of healthy horses; however, there were few differences among horses with IAD, horses with COPD during remission, and healthy horses. Most variables for forced expiration (FE) in horses with COPD or IAD differed significantly from those for healthy horses. Results of clinical examination had low to moderate sensitivity and predictive values for a diagnosis of COPD (range, 67 to 80%). Results of FE tests had high sensitivity, specificity, and predictive values for a diagnosis of COPD (79 to 100%), and results of standard lung mechanics tests had low sensitivity and predictive values (22 to 69%). Percentage of neutrophils in BAL fluid was highly sensitive (100%) but moderately specific (64%) for a diagnosis of COPD.

CONCLUSIONS AND CLINICAL RELEVANCE

Clinical examination is moderately accurate for establishing a diagnosis of COPD. Forced expiration tests can specifically detect early signs of airway obstruction in horses with COPD and IAD that may otherwise be inapparent. Cytologic evaluation of BAL fluid allows early detection of inflammatory respiratory disease, but it is not specific for COPD.

Tracheobronchial mucus viscoelasticity during environmental challenge in horses with recurrent airway obstruction

The goal of this study was to compare the rheological properties of mucus from horses with recurrent airway obstruction (RAO) to that from healthy controls during environmental challenge by stabling in stalls with straw as bedding and hay as feed. We determined viscoelasticity (log G* dyn/cm2, at 10 radian/s) and calculated mucociliary clearability index (MCI) and cough clearability index (CCI), which are derivative parameters of G* and the ratio of viscosity and elasticity measured at 1 and 100 radian/s, respectively. We also investigated the solids content of mucus, and cytology of bronchoalveolar lavage fluid (BALF). Samples were obtained before (0 h) and 6, 24 and 48 h after environmental challenge. The central findings were rheological changes in airway mucus, which occurred over time in RAO-affected animals, but not in controls. Mucus rheology was similar in both groups at 0 and 6 h. In RAO-affected horses, mucus viscoelasticity, as measured by log G*, increased from 2.49 +/- 0.18 dyn/cm2 (mean +/- s.e.) at 0 h to 3.05 +/- 0.13 dyn/cm2 at 24 h after environmental challenge, and was accompanied by significant decreases in MCI and CCI. Percent solids of mucus did not differ significantly between the 2 groups, nor over time. Rheological values did not correlate with BALF cytology. We conclude that viscoelastic properties of tracheal mucus samples from RAO horses in remission do not differ from those of normal horses. However, environmental challenge causes clinical signs of small airway disease and a concurrent increase in mucus viscoelasticity only in RAO horses. Therefore, we infer that unfavourable changes in mucus rheology may contribute to stasis and accumulation of mucus in RAO horses in exacerbation, but not in clinical remission.

Attitudes of Australian veterinarians about the cause and treatment of lower-respiratory-tract disease in racehorses

A questionnaire was administered to members of the Australian Equine Veterinary Association to investigate their attitudes and behaviours regarding the cause, diagnosis and treatment of lower-respiratory-tract disease in racehorses. The most-important perceived risk factors related to the level of exposure and resistance to infectious agents, whereas factors associated with racing and climatic factors were lower ranked. By far the most-commonly implicated primary cause of disease was respiratory viruses. However, specific diagnostic tests (such as viral serology or virus isolation) were rarely performed. By far the most-common diagnostic procedure was auscultation (without a rebreathing bag). The relative importance of diagnostic procedures was influenced by the proportion of total workload comprising horse work. Many respondents believed that bacteria become secondarily involved in disease; accordingly, antibiotic therapy was the most-commonly reported therapy. However, bacteriology of lower-airway-fluid samples was not commonly performed. The most-commonly used antibiotics were the potentiated sulphonamides (either alone or in combination with mucolytics or bronchodilators), followed by procaine penicillin and penicillin combined with gentamicin. Mainly, treatment would appear to be based on empirical beliefs rather than exhaustive investigation of individual cases.

Equine T-cell cytokines. Protection and pathology

The ultimate reason for better characterizing the immune response to infectious agents is the hope that this knowledge may lead to the development of better preventative or therapeutic measures. As more information becomes available, it becomes possible to incorporate these findings into the design of better vaccines and treatments. Likewise, attempts to either enhance or suppress specific helper T-cell responses may be required to control immunopathologic reactions. Although cytokine intervention in the clinical setting remains theoretic at this time, future manipulation based on the TH1/TH2 paradigm is probable.

Effect of a set stabled environmental control on pulmonary function and airway reactivity of COPD affected horses

The aim of this study was to evaluate the respiratory function of horses affected with chronic obstructive pulmonary disease (COPD) when maintained in a barn on wood shavings and fed grass silage for a period of 6 weeks. The mechanics of breathing, blood gas analysis and bronchial reactivity were examined on five horses with COPD at the end of the environment-controlled period (Period B) and the results compared with values obtained after 2 months at pasture (Period A) and after the onset of clinical signs of acute crisis (Period C). The results showed that clinical and functional parameters were similar in healthy horses and in COPD horses placed on pasture or stabled and fed grass silage. Moreover, the bronchial reactivity of COPD horses at pasture was similar to the bronchial reactivity of healthy horses. COPD horses fed grass silage however presented a bronchial reactivity intermediate between those measured after Period A and Period C which suggested they would be more susceptible to develop bronchoconstriction when in contact with inhaled irritants.

Environmental control to maintain stabled COPD horses in clinical remission: effects on pulmonary function

The objective of this study was to test the hypothesis that stabled COPD horses can be maintained in clinical remission by replacing hay by grass silage and bedding made of wood shavings (Period B) and of wheat straw (Period C) during 6 weeks, respectively. At the end of these different periods, the pulmonary function of the horses was assessed by mechanics of breathing and arterial blood analyses. These results were compared to those measured in clinical remission obtained after 2 months in pasture (Period A). No significant difference was observed between these 3 periods neither to values obtained for healthy horses placed during 6 weeks in a hay environment. For all that, COPD horses placed in contact with hay in the same barn developed within mean +/- s.d. 8+/-3 days clinical signs of heaves and significant alterations of pulmonary function parameters.

Equine pulmonary disease: a case control study of 300 referred cases. Part 1: Examination techniques, diagnostic criteria and diagnoses

Three-hundred adult horses, referred from 1990 to 1993 inclusively, for pulmonary examination were assessed using standardised history taking and clinical, intrapleural pressure, arterial blood gases and pH, bronchoscopic and tracheal and broncho-alveolar lavage fluid (BALF) cytological examinations. Two-hundred and thirty-five cases were referred with overt signs of pulmonary disease and the remaining 65 cases were referred for pulmonary examination because of reduced exercise (usually racing) performance or prolonged dyspnoea after racing. No pulmonary disease was detected in 30 cases. The 270 horses with pulmonary disease included 148 cases (54.8%) of chronic obstructive pulmonary disease (COPD), 45 (16.7%) of infectious or post infectious pulmonary disease, 7 (2.6%) of Streptococcus zooepidemicus pulmonary infection, 7 (2.6%) of lungworm infection, 16 (5.9%) of primary exercise induced pulmonary haemorrhage (EIPH), 9 (3.3%) of chronic idiopathic hypoxaemia, 20 (7.4%) of miscellaneous identified pulmonary disorders and 18 (6.7%) of undifferentiated pulmonary disorders. Two cases of primary summer associated obstructive pulmonary disease (SPAOPD) were observed, but 9.5% of COPD affected horses additionally suffered from SPAOPD.

Equine pulmonary disease: a case control study of 300 referred cases. Part 4: Treatments and re-examination findings

One-hundred and forty-seven of 270 (54.4%) horses suffering from pulmonary disorders were given at least one re-examination including, clinical, bronchoscopic, pulmonary function and cytological examinations after treatment and a further 83 of these horses (30.7%) had their clinical progress assessed by verbal or written reports. These examinations and progress reports showed high levels of partial or total recovery for most pulmonary disease categories, including chronic obstructive pulmonary disease, infectious, S. zooepidemicus and undifferentiated pulmonary disease and lungworm infection groups but not for the miscellaneous pulmonary disease (40% of these cases died), idiopathic chronic hypoxaemic or exercise induced pulmonary haemorrhage groups.

Equine pulmonary disease: a case control study of 300 referred cases. Part 3: Ancillary diagnostic findings

The majority of 270 adult horses with chronic pulmonary diseases had excessive volumes of respiratory secretions (RS) present in their trachea, elevated tracheal RS neutrophil ratios and lowered arterial oxygen partial pressures. Some control horses, had inexplicably elevated trachael RS neutrophil ratios. Only the chronic obstructive pulmonary disease (COPD) affected group had significantly elevated bronchoalveolar lavage fluid (BALF) neutrophil ratios. Maximal intrapleural pressure changes (max dPpl) were raised in 48% of COPD cases and rarely with other pulmonary disorders. Arterial pH or carbon doxide partial pressures values were seldom altered with any pulmonary diseases. Tracheal RS and BALF eosinophil ratios were raised with lungworm infection and idiopathic pulmonary eosinophilia.