Bronchoalveolar lavage fluid in Standardbred racehorses: Influence of unilateral/bilateral profiles and cut-off values on lower airway disease diagnosis

Bilateral bronchoalveolar lavage cytology profiles in a warmblood horse population during a 1-year period

BACKGROUND

Bronchoalveolar lavage (BAL) cytology results from 1 lung might not be representative of both lungs.

OBJECTIVES

To determine whether the lung site sampled would influence the horse's BAL cytology profile, and if a pooled BAL sample would be superior with regard to BAL cytology diagnosis in a cohort of healthy and subclinical asthmatic warmblood horses.

ANIMALS

Fifty-nine horses in 2021 and 70 horses in 2022, the follow-up included 53 of the same in each year.

METHODS

A cross-sectional study with follow-up included BAL cytology samples from individual lungs and from pooled BAL samples. The BAL samples were enumerated and differential cell count were applied to categorize the horses as control or with airway inflammation (AI).

RESULTS

Bronchoalveolar lavage mast cell count was higher in left lung compared to right lung (2021; median 1.6 [range, 0.6-3.3] vs 1.2 [0.7-1.5] P = .009, 2022; median 3.1 [2.1-4.2] vs 2.4 [1.7-3.4], P < .001) and compared to pooled samples (2022; median 2.6 [1.7-3.7], P < .001). Between year 2021 and 2022, 17 of the horses had changes in BAL cytology from control to AI or vice versa.

CONCLUSIONS AND CLINICAL IMPORTANCE

Pooled BAL sample was the least reliable for detecting AI, and was not representative of the overall lung condition.

Cytological diagnosis of exercise-induced pulmonary haemorrhage: Comparison of tracheal wash and bronchoalveolar lavage in standardbred racehorses

BACKGROUND

Cytology of airway samples is sensitive for diagnosis of exercise-induced pulmonary haemorrhage (EIPH), but the association between tracheal wash (TW) and bronchoalveolar lavage fluid (BALF) is unknown. The objective of this study was to determine whether diagnosis of EIPH, using haemosiderophages/macrophages (H/M) ratio, differs when based on TW or BALF.

METHODS

A prospective cross-sectional study was conducted on 102 standardbred horses in training. TW and BALF were collected concomitantly from all horses at rest (at least 24 hours after their last training or race), and their H/M ratios were calculated. Spearman's correlation, Cohen's kappa and Gwet's coefficient tests were performed to evaluate the association between TW and BALF samples.

RESULTS

With BALF, 21 horses met the cytological inclusion criteria for an EIPH diagnosis from individual and/or pooled samples. With TW, 20 horses had occasional (H/M < 10%) haemosiderophages, and nine, one and three horses had small (10%-25%), moderate (25%-50%) and large (>50%) proportions, respectively. Poor correlations and inconsistent concordances between TW and BALF were found for H/M ratio.

LIMITATIONS

Limitations include the use of a single staining method and the absence of a total haemosiderin score.

CONCLUSION

No association between TW and BALF was found for the cytological diagnosis of EIPH. Based on H/M ratio, BALF remains the sample type of choice for cytological diagnosis of EIPH.

Detection of fungi in the airways of horses according to the sample site: a methodological study

Fungal detection in equine airways may be performed on either tracheal wash (TW) or bronchoalveolar lavage fluid (BALF) by either cytology or culture. However, method comparisons are sparse. Our objective was to determine the prevalence of fungi in airways of horses according to the sample site and laboratory methodology. Sixty-two adult horses, investigated in the field or referred for respiratory disease, were included. Tracheal wash, and BALF collected separately from both lungs, were collected using a videoendoscope. Fungi were detected in cytologic samples examined by light microscopy, and by fungal culture. Hay was sampled in the field. Prevalence of fungi was of 91.9% in TW and 37.1% in BALF. Fungi were cultured from 82.3% of TW and 20.9% of BALF. Fungal elements were observed cytologically in 69.4% of TW and 22.6% of BALF. In 50% of horses, the same fungi were detected in both TW and hay, but fungi detected in BALF and hay differed in all horses. Poor agreement was found for the detection of fungi between TW and BALF and between fungal culture and cytologic examination (Cohen's kappa coefficient (κ) < 0.20). Moderate agreement was found between cytologic examination of left and right lungs (κ = 0.47). The prevalence of fungi detected cytologically on pooled BALF was significantly different (p = 0.023) than on combined left and right BALF. Fungi were more prevalent in the TW than BALF, and results suggest that hay might not be the primary source of fungi of the lower respiratory tract of horses.

Lipid species profiling of bronchoalveolar lavage fluid cells of horses housed on two different bedding materials

The lipidome of equine BALF cells has not been described. The objectives of this prospective repeated-measures study were to explore the BALF cells' lipidome in horses and to identify lipids associated with progression or resolution of airway inflammation. BALF cells from 22 horses exposed to two bedding materials (Peat 1-Wood shavings [WS]-Peat 2) were studied by liquid chromatography-tandem mass spectrometry (LC-MS/MS). The effects of bedding on lipid class and species compositions were tested with rmANOVA. Correlations between lipids and cell counts were examined. The BALF cells' lipidome showed bedding-related differences for molar percentage (mol%) of 60 species. Whole phosphatidylcholine (PC) class and its species PC 32:0 (main molecular species 16:0_16:0) had higher mol% after Peat 2 compared with WS. Phosphatidylinositol 38:4 (main molecular species 18:0_20:4) was higher after WS compared with both peat periods. BALF cell count correlated positively with mol% of the lipid classes phosphatidylserine, sphingomyelin, ceramide, hexosylceramide, and triacylglycerol but negatively with PC. BALF cell count correlated positively with phosphatidylinositol 38:4 mol%. In conclusion, equine BALF cells' lipid profiles explored with MS-based lipidomics indicated subclinical inflammatory changes after WS. Inflammatory reactions in the cellular lipid species composition were detected although cytological responses indicating inflammation were weak.

Effect of Lavage Solution Type on Bronchoalveolar Lavage Fluid Cytology in Clinically Healthy Horses

Equine bronchoalveolar lavage (BAL) is usually performed with 250-500 mL of isotonic saline at pH 5.5. The acidic pH of saline may cause an increase in airway neutrophil count 48 h after BAL. Other isotonic solutions such as Ringer's solution, phosphate-buffered saline (PBS) or Plasma-Lyte 148® have a neutral pH of 7.4 and might be a better choice for BAL by not provoking inflammation and the influx of neutrophils into airways. BAL was performed in four healthy horses in four different lung lobes using four different solutions in a randomized crossover design. In each lobe, BAL was performed twice with a 48 h interval using 250 mL of solution. Automated total nucleated cell counts (TNCs) were recorded, and differential cell counts in lavage fluid were determined by two investigators blinded to treatments. The mean volume of BAL fluid retrieved was 51 ± 14%. The mean neutrophil percentage (%N) increased from 1.5 ± 0.9% to 14.7 ± 9.6% at 48 h (p < 0.001) but was not significantly affected by the solution used or the lung lobe sampled. In conclusion, in this study, the influx of neutrophils into airways after BAL was independent of the type of isotonic solution used and the lung lobe sampled. Saline remains an appropriate solution for BAL in horses.

Medical causes of poor performance and their associations with fitness in Standardbred racehorses

BACKGROUND

Poor performance is a multifactorial syndrome of racehorses, commonly associated with subclinical disorders, which can be diagnosed by exercise testing.

OBJECTIVES

Describe the prevalence of medical causes of poor performance in Standardbreds unassociated with lameness, and evaluate their relationships with fitness variables measured by exercise treadmill test.

ANIMALS

Hospital population of 259 nonlame Standardbred trotters referred for poor performance.

METHODS

The horses' medical records were retrospectively reviewed. Horses underwent a diagnostic protocol including resting examination, plasma lactate concentration, treadmill test with continuous ECG and assessment of fitness variables, creatine kinase activity, treadmill endoscopy, postexercise tracheobronchoscopy, bronchoalveolar lavage (BAL), and gastroscopy. The prevalence of different disorders was evaluated, including cardiac arrhythmias, exertional myopathies, dynamic upper airway obstructions (DUAOs), exercise-induced pulmonary hemorrhage (EIPH), moderate equine asthma (MEA), and gastric ulcers (EGUS). The associations of these disorders with fitness variables were investigated individually and using multivariable models.

RESULTS

Moderate equine asthma and EGUS were the most common disorders, followed by EIPH, DUAOs, cardiac arrhythmias, and exertional myopathies. Hemosiderin score was positively correlated with BAL neutrophils, eosinophils, and mast cells; increased creatine kinase activity was associated with BAL neutrophilia, DUAOs, premature complexes, and squamous gastric disease. Treadmill velocity at a plasma lactate concentration of 4 mmol/L and at heart rate of 200 beats per minute was negatively affected by BAL neutrophilia, multiple DUAOs, exertional myopathies, and squamous gastric disease.

CONCLUSIONS

The multifactorial nature of poor performance was confirmed, with MEA, DUAOs, myopathies and EGUS representing the main diseases involved in fitness impairment.

A Scoping Review of Non-Structural Airway Disease as a Cause of Poor Performance in Racehorses

The association between poor performance and respiratory disease in Thoroughbred racehorses that do not have a structural abnormality of the respiratory tract, is often based on anecdotal evidence. The objective of this scoping review was to examine the scientific evidence for such associations. Publications were selected based on a search of three databases (PubMed, Scopus, and CAB Direct), in English and without date restriction, followed by a screening process to exclude non-relevant papers, duplicates, and reviews. This process identified 996 publications of which 20 were analysed using the Quality in Prognosis Studies (QUIPS) tool. The results indicated that the evidence supporting the relationship between proposed diagnostic indicators and poor performance is variable. There is a need for better quality evidence. In particular, there are conflicting reports relating to the impact of equine asthma and EIPH on athletic performance. Furthermore, a lack of standardisation in the measurement of racehorse performance makes it difficult to compare findings from different studies. The industry would benefit from high-level guidance concerning the design of controlled performance studies in Thoroughbred racehorses to collect comprehensive data and facilitate targeted interventions.

Cytologic scoring of equine exercise-induced pulmonary hemorrhage: Performance of human experts and a deep learning-based algorithm

Exercise-induced pulmonary hemorrhage (EIPH) is a relevant respiratory disease in sport horses, which can be diagnosed by examination of bronchoalveolar lavage fluid (BALF) cells using the total hemosiderin score (THS). The aim of this study was to evaluate the diagnostic accuracy and reproducibility of annotators and to validate a deep learning-based algorithm for the THS. Digitized cytological specimens stained for iron were prepared from 52 equine BALF samples. Ten annotators produced a THS for each slide according to published methods. The reference methods for comparing annotator's and algorithmic performance included a ground truth dataset, the mean annotators' THSs, and chemical iron measurements. Results of the study showed that annotators had marked interobserver variability of the THS, which was mostly due to a systematic error between annotators in grading the intracytoplasmatic hemosiderin content of individual macrophages. Regarding overall measurement error between the annotators, 87.7% of the variance could be reduced by using standardized grades based on the ground truth. The algorithm was highly consistent with the ground truth in assigning hemosiderin grades. Compared with the ground truth THS, annotators had an accuracy of diagnosing EIPH (THS of < or ≥ 75) of 75.7%, whereas, the algorithm had an accuracy of 92.3% with no relevant differences in correlation with chemical iron measurements. The results show that deep learning-based algorithms are useful for improving reproducibility and routine applicability of the THS. For THS by experts, a diagnostic uncertainty interval of 40 to 110 is proposed. THSs within this interval have insufficient reproducibility regarding the EIPH diagnosis.

Effects of low-dust forages on dust exposure, airway cytology, and plasma omega-3 concentrations in Thoroughbred racehorses: A randomized clinical trial

BACKGROUND

Racehorses commonly develop evidence of mild asthma in response to dust exposure. Diets deficient in omega-3 polyunsaturated fatty acids (Ω-3) might exacerbate this response.

HYPOTHESIS

To compare dust exposure, bronchoalveolar lavage fluid (BALF) cytology, and plasma Ω-3 and specialized pro-resolving mediators (SPM) concentrations amongst racehorses fed dry hay, steamed hay, and haylage.

ANIMALS

Forty-three Thoroughbred racehorses.

METHODS

Prospective clinical trial. Horses were randomly assigned to be fed dry hay, steamed hay, or haylage for 6 weeks. Measures of exposure to dust in the breathing zone were obtained twice. At baseline, week-3, and week-6, BALF cytology was examined. Plasma lipid profiles and plasma SPM concentrations were examined at baseline and week 6. Generalized linear mixed models examined the effect of forage upon dust exposure, BALF cytology, Ω-3, and SPM concentrations.

RESULTS

Respirable dust was significantly higher for horses fed hay (least-square mean ± s.e.m. 0.081 ± 0.007 mg/m³ ) when compared with steamed hay (0.056 ± 0.005 mg/m³ , P = .01) or haylage (0.053 ± 0.005 mg/m³ , P < .01). At week 6, BALF neutrophil proportions in horses eating haylage (3.0% ± 0.6%) were significantly lower compared with baseline (5.1 ± 0.7, P = .04) and horses eating hay (6.3% ± 0.8%, P < .01). Plasma eicosapentaenoic acid to arachidonic acid ratios were higher in horses eating haylage for 6 weeks (0.51 ± 0.07) when compared with baseline (0.34 ± 0.05, P < .01) and horses eating steamed (0.24 ± 0.02, P < .01) or dry hay (0.25 ± 0.03, P < .01).

CONCLUSIONS AND CLINICAL IMPORTANCE

Steamed hay and haylage reduce dust exposure compared with dry hay, but only haylage increased the ratio of anti-inflammatory to pro-inflammatory lipids while reducing BAL neutrophil proportions within 6 weeks.

Mild-moderate equine asthma: A scoping review of evidence supporting the consensus definition

Current consensus defines mild-moderate equine asthma (mEA; previously inflammatory airway disease) by a hierarchy of indicators of lung pathology: cough, poor performance, increased tracheobronchial mucus, inflammatory bronchoalveolar lavage (BAL) cytology and pulmonary dysfunction. Exclusion criteria include fever, systemic disease, or increased resting respiratory effort. The aim of this review was to inform future research by identifying gaps, strengths and weaknesses in the current body of evidence supporting this consensus-proposed definition. Objectives were to critique evidence supporting the inclusion of each diagnostic indicator in the case definition, by summarising and evaluating evidence for its association with higher-level indicators of lung inflammation. Searches of three databases identified 2275 articles relating to mEA or its diagnostic indicators, from which 298 full-text articles were screened and 45 reviewed in full. Studies (n = 44) had been performed worldwide in clinics, hospitals, racetracks, yards or research herds, in 6092 horses. Studies were predominantly opportunistic observational (n = 13/44: 29.5%) or cross-sectional (n = 11/44; 25%). The median number of horses per study was 74. Where breed and use were reported most were Thoroughbreds (58.2%; 2730/4688) and racehorses (72.8%; n = 3960/5439). Domains rated as high risk of bias in almost 50% of articles were 'study power' and 'masking'. Heterogeneity in clinical and laboratory measures precluded meta-analysis. Evidence was more consistent for certain pairwise relationships (e.g., between cough and tracheobronchial mucus) than others (e.g., BAL cytology and lung function). Findings highlight the need for increased standardisation of diagnostic methods and reporting to facilitate future systematic review and meta-analysis.

Bilateral thoracic radiographs increase lesion detection in horses with pneumonia or pulmonary neoplasia but do not bring any additional benefit for inflammatory or diffuse pulmonary disease

Published studies describing the effects of bilateral radiographic projections on the detection of equine pulmonary lesions are currently lacking. The objectives of this retrospective, single center, observational study were to compare unilateral and bilateral thoracic radiographic projections for the detection of pulmonary lesions in a group of horses. Based on their clinical diagnosis, 167 adults and foals with bilateral thoracic radiographs were classified as having pneumonia (n = 88), inflammatory or diffuse pulmonary disease (n = 72), and pulmonary masses (n = 7). After an initial interrater repeatability test, right-to-left and left-to-right projections were anonymized and independently interpreted by a radiologist blinded to the clinical diagnosis. Scores were attributed for each pattern/lesion (alveolar, interstitial, bronchial, nodules/masses, cavitary lesions) and each quadrant. Agreement between scores from each projection was evaluated with Bland-Altman plots. Lesions identified on one side but not on the contralateral projection were considered discordant. There was no preferential lateralization of pulmonary lesions. The prevalence of discordance was 14.4%, 9.0%, and 4.2% for alveolar pattern, nodules/masses, and cavitary lesions, respectively. Up to nine horses (10.2%) with pneumonia could have been misdiagnosed. A pulmonary mass would have been missed in one case. For inflammatory or diffuse disease, discordance was slight, and the addition of contralateral projections had no impact on radiographic interpretation. In conclusion, in horses with pneumonia or neoplasia, bilateral projections, or adding at least one contralateral caudoventral view, increased the probability of identifying pulmonary lesions. In horses with inflammatory or diffuse disease, bilateral thoracic radiography provided no additional benefit.

The Role of Thoracic Ultrasonography and Airway Endoscopy in the Diagnosis of Equine Asthma and Exercise-Induced Pulmonary Hemorrhage

Mild-moderate (MEA), severe (SEA) equine asthma and exercise-induced pulmonary hemorrhage (EIPH) are common respiratory disorders in horses. The present retrospective study aims to evaluate the role of ultrasonography and endoscopy in the diagnosis of these conditions. Three hundred and three horses were included and divided into SEA, MEA and MEA + EIPH groups, on the basis of history, clinical examination and bronchoalveolar lavage fluid (BALf) cytology; scores were assigned to lung ultrasonography, pharyngeal lymphoid hyperplasia (PLH), tracheal mucus (TM) and tracheal bifurcation edema (TB). These scores were compared between groups, and their associations with age, BALf cytology, tracheal wash microbiology and between endoscopic and ultrasonographic scores were statistically analyzed. Ultrasonographic scores were higher in the SEA and MEA + EIPH groups and associated with increased BALf neutrophils and hemosiderophages. The PLH score was higher in younger horses affected by MEA and EIPH and associated with increased eosinophils and hemosiderophages. TM and TB scores were greater in older horses affected by SEA, associated with increased neutrophils and inversely correlated with hemosiderophages. Moreover, TM grade was negatively correlated with mast cells. Thoracic ultrasonography and airway endoscopy can provide useful information about the inflammatory status of upper and lower airways in the horse.

Use of external nasal strip influences alveolar cell population of horses after exercise

ABSTRACT The nasal strip is widely used in horses during exercise, but effects of using a nasal strip are controversial and little is known about its effect on horses undergoing endurance events. The aim of this study was to determine whether the use of nasal strips influences alveolar cell population assessed by bronchoalveolar lavage (BAL), tidal volume, and nasal airflow rate. Six Arabian horses were subjected to two low intensity tests on a treadmill, with and without application of a commercial external nasal strip. Tidal volumes and airflow rates were measured during the test; two hours after the test, BAL was performed to assess cytology of pulmonary secretions. The lavage fluid showed increased neutrophil count after exercise in animals with the nasal strip (P<0.05). This suggests that turbulence of airflow through the nasal cavity may have diminished with nasal strip use, thus allowing larger particles to be deposited more distally in the respiratory system, inducing a more intense neutrophilic response. No differences in tidal volumes or airflow rates were observed between groups (with or without nasal strips) during the test (P>0.05). The use of nasal strips seems to influence alveolar cell population during and after exercise in horses after low intensity exercise tests. Further studies are needed to verify whether alveolar cell population is related to poor exercise performance in horses.

Application across species of a one health approach to liquid sample handling for respiratory based -omics analysis

Airway inflammation is highly prevalent in horses, with the majority of non-infectious cases being defined as equine asthma. Currently, cytological analysis of airway derived samples is the principal method of assessing lower airway inflammation. Samples can be obtained by tracheal wash (TW) or by lavage of the lower respiratory tract (bronchoalveolar lavage (BAL) fluid; BALF). Although BALF cytology carries significant diagnostic advantages over TW cytology for the diagnosis of equine asthma, sample acquisition is invasive, making it prohibitive for routine and sequential screening of airway health. However, recent technological advances in sample collection and processing have made it possible to determine whether a wider range of analyses might be applied to TW samples. Considering that TW samples are relatively simple to collect, minimally invasive and readily available in the horse, it was considered appropriate to investigate whether, equine tracheal secretions represent a rich source of cells and both transcriptomic and proteomic data. Similar approaches have already been applied to a comparable sample set in humans; namely, induced sputum. Sputum represents a readily available source of airway biofluids enriched in proteins, changes in the expression of which may reveal novel mechanisms in the pathogenesis of respiratory diseases, such as asthma and chronic obstructive pulmonary disease. The aim of this study was to establish a robust protocol to isolate macrophages, protein and RNA for molecular characterization of TW samples and demonstrate the applicability of sample handling to rodent and human pediatric bronchoalveolar lavage fluid isolates. TW samples provided a good quality and yield of both RNA and protein for downstream transcriptomic/proteomic analyses. The sample handling methodologies were successfully applicable to BALF for rodent and human research. TW samples represent a rich source of airway cells, and molecular analysis to facilitate and study airway inflammation, based on both transcriptomic and proteomic analysis. This study provides a necessary methodological platform for future transcriptomic and/or proteomic studies on equine lower respiratory tract secretions and BALF samples from humans and mice.

Evaluation of Treatment With Respiratory Gene Technology and Serum in a Group of Standard Bred Racehorses With Cytological Evidence of Mild Equine Asthma

Alternative treatment options to glucocorticoids for equine asthma is desirable due to withdrawal time. The objective was to evaluate if serum and Respiratory Gene Technology (RGT), a commercial kit to produce autologous conditioned serum, was effective in reducing bronchoalveolar lavage (BAL) neutrophils and mast cells in racehorses with cytological evidence of mild equine asthma . Thirty-six Standardbred trotters in active training were enrolled in this randomized clinical trial; a healthy control group (n=11), a RGT group (n=12) and a serum group (n=13). Endoscopy including tracheal wash (TW) and BAL was performed before (T0), after a 6-week treatment period including 12 intramuscular injections of RGT or serum (T6) and as a follow-up 10 weeks after treatment (T16). A significant decrease in BAL neutrophils for the RGT group was found between T0 and T6 (P = .002, d=-1.51, CI: -2.43;-0.59) and for the serum group between T0-T6 (P = .002, d=-1.36, CI: -2.26;-0.46). Further, a significant decrease in BAL mast cells between T0-T6 for the both the RGT group (P = .019, d=-1.23, CI: -1.22;-0.34) and the serum group (P= .004, d=-0.81, CI: -1.65;0.04), and further between T0-T16 (RGT P= .011, d=-1.55, CI: -2.62;-0.48; serum P= .044, d=-0.65, CI: -1.68;-0.37). No significant difference in TW cytology was found for any of the time-points. Pro- and anti-inflammatory cytokines were regulated according to treatment. The control group showed no cytological differences between any time-point. Study results showed that intramuscular treatment with both RGT and serum was effective associated with reduction of BAL neutrophils and mast cells in horses with cytological evidence of mild equine asthma. Further large-scale studies are necessary.

Comparison of Flowmetric Plethysmography and Forced Oscillatory Mechanics to Measure Airway Hyperresponsiveness in Horses

Airway hyperresponsiveness (AHR) is linked to airway inflammation and is considered a key manifestation of mild/moderate equine asthma (EA). The study purpose was to determine whether two modalities of non-invasive lung function testing (FOM-forced oscillatory mechanics vs. FP-flowmetric plethysmography) establish the same clinical diagnosis of AHR in horses, using histamine bronchoprovocation. Nineteen horses (3-25 years, 335-650 kg) with clinical signs suggestive of mild/moderate equine asthma were enrolled. FOM and FP testing was performed in each horse on two consecutive days, using a randomized cross-over design. AHR was defined by the histamine dose needed to double FOM baseline resistance, or to achieve a 35% increase in FP delta flow. Bronchoalveolar lavage fluid (BALF) was subsequently collected and stained with modified Wright's and toluidine blue stains. Binary statistical tests (related samples T-test, Mann-Whitney U, Chi-square analyses) were performed to compare study groups, with P < 0.05 considered significant. Abnormal BALF cytology confirmed EA in 14/19 (73.7%) horses. Both FOM and FP revealed AHR in 7/14 (50%) of these EA horses. An additional 4/19 (21.1%) horses showed AHR based on FP but not FOM, including two horses with normal BALF cytology. A diagnosis of AHR was more often associated with FP than FOM (P = 0.013), although the prevalence of AHR was significantly higher in EA vs. non-EA horses, regardless of testing methodology. The phase angle between thoracic and abdominal components of breathing did not differ between test groups. In conclusion, FP diagnosed AHR more frequently than did FOM, including horses with no other diagnostic evidence of EA. Without further evaluation, these two testing modalities of AHR cannot be used interchangeably.

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.

Conflict Between Direct Experience and Research-Based Evidence Is a Key Challenge to Evidence-Based Respiratory Medicine on British Racing Yards

Inflammatory airway disease (IAD) is a commonly diagnosed but variably defined syndrome of equine lower airway inflammation. The most recent American College of Veterinary Internal Medicine (ACVIM) consensus statement, informed by research evidence, recommends a case definition based on clinical signs (poor performance or occasional coughing of at least 3 weeks duration), increased endoscopically-visible tracheal mucus, and bronchoalveolar lavage cytology, and proposes that the condition should be termed ‘mild-moderate equine asthma' (mEA). In British Thoroughbred racehorses, research to date has focused on airway inflammation defined by increased tracheal mucus and inflammatory tracheal wash sample cytology. It has been unclear whether or to what extent the ACVIM consensus statement has influenced the practice of British racing veterinarians. The aim of this qualitative study was to characterize and understand rationales for current practices relating to diagnosing and managing airway inflammation in British racehorses. Audio-recorded focus group discussions were conducted with 25 participants from four veterinary practices in England. Practices were purposively selected to represent those responsible for different types of racehorse, in different geographical regions. Thematic analysis of transcripts identified (i) an over-arching theme of serving the racing industry within which two further themes (ii) disregarding of the consensus and (iii) the pragmatic clinician were nested. The requirement to serve the racing industry was a key driver of clinical approaches, strongly influenced in particular by the trainer. Participants widely disregarded the consensus case definition of IAD/mEA for British racehorses because of perceived differences in etiology, perceived lack of practicability, particularly of BAL sampling, and perceived lack of understanding of the British racing context by consensus authors. Participants shared a strong professional identity as pragmatic clinicians providing an individualized clinical approach based on direct experience, which was often prioritized as the most valuable evidence with which to inform clinical decision-making. Lack of alignment with international consensus presents a barrier to practicing and furthering evidence-based medicine. Improved dialogue and partnership in research would be valuable and further research tailored for this population, including continuing development of contextually acceptable diagnostic methods, may be required.

Asymmetrical Pulmonary Cytokine Profiles Are Linked to Bronchoalveolar Lavage Fluid Cytology of Horses With Mild Airway Neutrophilia

Few data on cytokine profiles in bronchoalveolar lavage fluid (BALF) are available for racehorses with mild/moderate equine asthma (EA); cytological diagnosis being most frequently made from only one lung. The purpose of the study was to compare cytokine mRNA expressions and protein concentrations in BALF from both lungs. As part of a larger study, 250 ml saline was randomly instilled in one lung and 500 ml in the contralateral lung of 30 clinically healthy Standardbred racehorses. This procedure was repeated 72 h later, inversing the volume per lung. Cytological cut-off values for diagnosis of mild EA was neutrophil proportions > 10% when instilling 250 ml. Eleven horses that exhibited unilateral mild inflammatory cytology [i.e., normal cytology (<10% neutrophils) in the other lung] were enrolled. Protein concentrations were not significantly different between lungs, for any of the investigated cytokines. Relative mRNA expression of IL-1β (3.887 ± 0.929) and IL-10 (3.225 ± 0.516) were significantly higher in BALF from mild inflammatory lungs when compared with non-inflammatory ones (1.408 ± 0.337 and 1.488 ± 0.420, respectively); and also significantly correlated with neutrophil proportions (R = 0.45 and R = 0.58, respectively). These findings suggest that specific inflammatory response and/or regulation locally occurs within the lower airways.

Efficacy of dexamethasone, salbutamol, and reduced respirable particulate concentration on aerobic capacity in horses with smoke-induced mild asthma

Background

Mild asthma in horses decreases racing performance and impairs gas exchange. The efficacy of treatment on performance is unknown.

Hypothesis

Treatment targeting lung inflammation improves V˙O₂peak in horses with mild asthma.

Animals

Thoroughbred polo horses (n = 12) with smoke‐induced mild asthma. Horses were exposed to increased ambient particulate matter (35.51 μg/m³ [PM_2.5]; day mean, centrally measured) from day −33 to 0, from bushfire smoke (natural model).

Methods

Prospective, randomized, placebo‐controlled, double‐blinded clinical trial. All horses completed 3 V˙O₂peak tests, measuring aerobic and anaerobic variables: day 0 ‐baseline; day 16 ‐after dexamethasone (20 mg IM q24h; DEX, n = 6) or saline treatment (SALINE, n = 6), under improved ambient PM_2.5 concentrations (7.04 μg/m³); day 17‐15‐30mins after inhaled salbutamol (1500 μg). Bronchoalveolar lavage and mucus scoring were performed on day −8 and day 20. Linear mixed effects models were used to examine the effects of timepoint and treatment group on BAL differential cell counts, mucus scores, aerobic and anaerobic variables.

Results

Horses’ mucus scores improved significantly from day −8 to 20 by 1.27 ± .38 (P = .01). There was a significant increase in V˙O₂peak of 15.5 ± 4.0 mL(min.kg)⁻¹ from day 0 to 17 (P = .002), representing an average (mean) increase in V˙O₂peak of 13.2%. There was no difference in V˙O₂peak between treatment groups (SALINE versus DEX) at any timepoint.

Conclusions and Clinical Importance

This study highlighted the key role of improved air quality on functionally important airway inflammation. Evidence provided is central to increasing owner compliance regarding improved air quality for the treatment and prevention of mild asthma.

The relationship between bronchoalveolar lavage fluid cytology and airway hyper-reactivity in a population of Australian horses presented for poor performance

OBJECTIVE

To investigate the relationship between bronchoalveolar lavage fluid cytology, particularly mast cells, and airway hyper-reactivity in athletic horses presented for poor performance that included a respiratory tract evaluation in two disparate locations in Australia.

DESIGN

Multi-centre, retrospective and prospective cross-sectional study METHODS: Eighty four adult horses underwent both pulmonary function testing and histamine bronchoprovocation with a commercial flowmetric plethysmography system. A bronchoalveolar lavage was performed four to twelve hours later. Bronchoalveolar lavage fluid cytology was categorised using two differing classification systems to define mild equine asthma. Statistical analysis was used to assess associations between bronchoalveolar lavage fluid relative inflammatory cell percentages, and airway hyper-reactivity and their associated categorisations.

RESULTS

Sixty four percent (54/84) of horses displayed airway hyper-reactivity, as defined by PC₃₅  < 6 mg/ml of histamine. A relative mastocytosis was the most common bronchoalveolar lavage fluid cytological abnormality. Horses with a sole mast cell response of ≥ 5% within their bronchoalveolar lavage fluid displayed airway hyper-reactivity at a lower dose of nebulized histamine than horses with normal bronchoalveolar lavage fluid cytology. Horses with mixed cell responses (relative mast cell percentage > 2% and/or relative neutrophil percentage > 5% and/or eosinophil relative cell percentage ≥ 1%) displayed airway hyper-reactivity at a lower dose of nebulized histamine than horses with normal bronchoalveolar lavage fluid cytology.

CONCLUSION

In the Australian context, recently revised increased bronchoalveolar lavage fluid cytology relative cell percentage cut offs appear appropriate for sole mast cell responses. The historical lower cut offs appear to be appropriate for mixed inflammatory cell responses.

Exercise-induced Pulmonary Hemorrhage: Is It Important and Can It Be Prevented?

Exercise-induced pulmonary hemorrhage (EIPH) occurs commonly in horses undergoing strenuous exercise. Reported risk factors include racing in cold temperatures and wearing of bar shoes. In horses with documented moderate to severe EIPH, increasing the interval between races and adopting a negative race pace strategy may reduce the severity of EIPH in subsequent races. EIPH seems to have an impact on performance only when moderate to severe. This occurs in a small number of starters, approximately 6%. EIPH often is erratic in severity from race to race, although across a population it is weakly progressive over increasing race starts.

Bronchoalveolar Lavage Cytology Characteristics and Seasonal Changes in a Herd of Pastured Teaching Horses

Equine asthma syndrome (EAS) is a common problem that affects horses of any age. Severe EAS is reported to affect 10-20% of adult horses in the northern hemisphere, while mild/moderate EAS is reported to affect 60-100% of adult horses, depending on the population and geographic region. For both severe and mild/moderate EAS, the presence of lower airway inflammation is attributed to airborne "triggers" such as dust, mold, and bacterial components that horses encounter in hay and stable-environments; and treatment recommendations for horses with EAS often include full-time pasture turnout. The caveat to this recommendation is horses with summer-pasture associated EAS (SP-EAS), who experience allergic lower airway inflammation when exposed to summer pasture. The prevalence of EAS in horses on pasture that do not have SP-EAS has not been reported. The purpose of this study was to use bronchoalveolar lavage (BAL) cytology to determine the prevalence of EAS in a herd of pastured, adult research horses with no history of respiratory disease. The horses were members of a teaching animal herd housed on pasture in the southeastern United States and fed round-bale Bermuda-grass hay. BAL fluid (BALF) cytology was analyzed in both summer (May-August 2017) and winter (November 2017-February 2018). Similar to previous reports, the prevalence of severe EAS in our study population was 10% in summer and 4.3% in winter. The prevalence of mild/moderate EAS was 60% in summer and 87% in winter. The high prevalence of mild/moderate EAS in this population was unexpected, given the 24-h, year-round pasture environment and the lack of history of respiratory disease. Additionally, 61.1% of horses with both summer and winter data had a different BALF cytology profile between the two seasons. To the authors' knowledge, this is the first study to use BAL cytology to diagnose, and monitor changes in, EAS phenotype in pastured adult horses. These results help to inform discussions regarding prevalence of EAS in pastured, adult horses in the southeastern region of North America.

The Effect of Race Training on the Basal Gene Expression of Alveolar Macrophages Derived From Standardbred Racehorses

Mild-to-moderate equine asthma is prevalent in young racehorses, particularly early in their training period. Although the precise etiopathogenesis remains undetermined, it is possible that the susceptibility of this population might partly reflect an exercise-associated immune derangement at the level of the airway. We performed a genome-wide basal gene expression scan on alveolar macrophages (AMs) isolated from Standardbred racehorses before and after commencement of competition race training with a view to identifying any exercise-associated gene expression modulation consistent with functional alterations, which might reflect training-associated immunological derangement. Microarray technology was used to analyze the basal gene expression profiles of bronchoalveolar fluid-derived AMs, harvested from six systemically healthy Standardbred racehorses before (T0) and after (T1) entry into training. In addition, AM lipopolysaccharide (LPS)-induced TNF-α and IL-10 release at T0 and T1 was assessed. Although the data revealed significant interhorse heterogeneity in relation to the magnitude of individual gene expression at each timepoint, within each horse, several inflammatory-related genes [e.g., chemokine ligands, interferons, and nuclear factor kappa-light-chain-enhancer of activated B cells (NFKB)] declined in expression from T0 to T1. Entry into training did not significantly alter AM LPS-induced TNF-α or IL-10 release. The data support a direct effect of training on AM basal gene expression, particularly with respect to immune-related genes. The pattern of training-associated differential gene expression may indicate relative downregulation of inflammatory-related genes, consistent with an immunosuppressive effect of training and an increased susceptibility to opportunistic pathogens.

Bronchoalveolar lavage fluid from both lungs in horses: Diagnostic reliability of cytology from pooled samples

Cytology of bronchoalveolar lavage fluid (BALF) from one lung may not predict findings in the contralateral lung of the same horse. The aim of this study was to determine whether a pooled BALF from both lungs was representative of corresponding individual samples. Fifty-one horses referred for poor performance and/or respiratory signs and for which a BALF was collected from both lungs, were included in the study. Cytology of pooled and individual BALF samples were performed using a masked protocol. Based on clinical signs and individual BALF cytologies, horses were classified as control (CTL), mild equine asthma (mEA), severe equine asthma (sEA) and/or exercise-induced pulmonary haemorrhage (EIPH). No significant difference was observed between pooled and individual BALF samples for all cell types (P>0.05). Correlations between pooled and individual BALF samples were good (r≥0.9) for neutrophil proportions and haemosiderophages/macrophages ratio, and moderate (r≥0.4) for metachromatic cell and eosinophil proportions. Similarly, intraclass correlation coefficient (ICC) were good (ICC≥0.9) for neutrophil proportions and haemosiderophages/macrophages ratio and substantial (ICC≥0.6) for metachromatic cell proportions. Based on threshold values for pooled samples as determined by receiver operating characteristic (ROC) analysis, categorical agreements were good (κ≥0.97) for diagnosis of mEA/sEA, and substantial (κ=0.74) for EIPH. Using a pooled BALF sample, only one horse was incorrectly classified as CTL instead of mEA and three horses were classified as EIPH instead of CTL. In conclusion, BALF cytology from pooled sample is representative of both individual lungs, and constitutes a valid method to diagnose EA.

The influence of hay steaming on clinical signs and airway immune response in severe asthmatic horses

Background

Avoidance of antigenic stimuli was found to significantly reverse airway obstruction of horses with severe equine asthma (sEA). To date, no published study investigated the influence of steaming hay on lower airway condition of sEA-affected horses. The objectives were to determine the clinical, cytological and cytokine respiratory responses of both sEA and control (CTL) horses experimentally exposed to steamed or dry hay.

Results

A cohort of 6 sEA horses and 6 CTL horses was involved in this field study. On day 0, both groups were fed with steamed hay for 5 consecutive days, followed by a wash-out period of 26 days prior to be fed with dry hay for 5 consecutive days. Investigations performed 2 days prior to and 5 days after each challenge included clinical score, tracheal mucus accumulation, and bronchoalveolar lavage fluid (BALF) cytology and cytokine mRNA expression. Feeding steamed hay significantly decreased its mould content (P < 0.001). Mucus score significantly increased when feeding dry hay (P = 0.01). No significant influence of challenge type was found on clinical score. Percentages of neutrophils (P < 0.001) as well as mRNA expression of IL-1β (P = 0.024), IL-6R (P = 0.021), IL-18 (P = 0.009) and IL-23 (P = 0.036) in BALF of sEA affected horses were significantly increased after both (steamed and dry hay) challenges. Relative mRNA expression of IL-1β, IL-6R and IL-23 in BALF were also significantly correlated to neutrophil percentages and both clinical and tracheal mucus score.

Conclusions

Steaming significantly decreased mould content but inconsistently influenced the respiratory response of sEA affected horses when fed hay. Based on BALF cytology and cytokine profiles, its relevance might be controversial as a non-medicinal therapy for sEA-affected horses.

Electronic supplementary material

The online version of this article (10.1186/s12917-018-1636-4) contains supplementary material, which is available to authorized users.

Bronchoalveolar lavage fluid cytology and airway hyper-reactivity in clinically normal horses

OBJECTIVE

To characterise the relationship between bronchoalveolar lavage fluid (BALF) cytology and pulmonary function testing with histamine bronchoprovocation (HBP) methods in a population of clinically normal horses.

DESIGN

Cross-sectional study METHODS: Clinically normal adult horses (n = 33) underwent pulmonary function testing and HBP with a commercial flowmetric plethysmography system. BAL was performed 1-5 days later. Statistical analysis was used to assess associations between BALF cell concentration, relative inflammatory cell percentages and categorisation, and airway hyper-reactivity (AHR).

RESULTS

AHR (PC₃₅  ≤ 8 mg/mL) was demonstrated in 17 (52%) of the horses. Using current definitions, BALF cytology was consistent with inflammatory airway disease in 14 (42%) of the horses and 7 of those demonstrated either mastocytic and/or eosinophilic responses. There was no correlation between total inflammatory cell counts or relative percentage and AHR. No statistical association was found between BALF inflammatory cell categories and AHR.

CONCLUSION

A direct association between cytological evidence of airway inflammation and AHR was not identified in this population of clinically normal horses. Determining the presence and measuring inflammatory cell mediators in BALF may more accurately reflect AHR. In addition, normal values for cell proportions in BALF may vary between different populations of horses and more appropriate regional reference ranges should be established.

An observational study of environmental exposures, airway cytology, and performance in racing thoroughbreds

Background

Mild equine asthma is presumed to arise in response to environmental exposures but the relative impact of differing inflammatory phenotypes upon performance are largely unexplored.

Hypotheses: Airway inflammation negatively affects performance and cytological phenotype varies with environmental exposure.

Animals

Thoroughbred racehorses in active training and racing.

Methods

Thoroughbreds were recruited 24‐48 hours before racing. Each horse was eligible for re‐enrollment with each race entry. Within one hour of race completion, physical examination, respiratory endoscopy, and BAL were performed. Respirable and inhalable dust, respirable endotoxin, and respirable β‐glucan exposures were measured at the breathing zone within one week after racing. Controlling for age, trainer, and pulmonary hemorrhage, the relationship between performance, bronchoalveolar lavage fluid (BALF) cytology, and measures of exposure were modeled.

Results

Performance and BALF data were collected on 64 individual horses from 8 stables for a total of 98 race performances and 79 dust exposure assessments. Evidence of mild equine asthma was found in 80% (78/98) of BALF samples from 52/64 horses. For each percent increase in BALF mast cell and neutrophil proportions, speed figures were reduced by 2.9 (P = .012) and 1.4 (P = .046) points, respectively. Respirable dust concentration was associated with BALF neutrophil proportions (P = .015). Bronchoalveolar lavage fluid mast cell proportions were only associated with respirable β‐glucan exposures (P = .030).

Conclusions and Clinical Importance: Mild equine asthma is common in racing horses and negatively impacts performance. The data support that respirable, rather than inhalable, dust exposure measures are pertinent to equine airway health.

Effect of a syringe aspiration technique versus a mechanical suction technique and use of N-butylscopolammonium bromide on the quantity and quality of bronchoalveolar lavage fluid samples obtained from horses with the summer pasture endophenotype of equine asthma

OBJECTIVE To evaluate the effect of 2 bronchoalveolar lavage (BAL) sampling techniques and the use of N-butylscopolammonium bromide (NBB) on the quantity and quality of BAL fluid (BALF) samples obtained from horses with the summer pasture endophenotype of equine asthma. ANIMALS 8 horses with the summer pasture endophenotype of equine asthma. PROCEDURES BAL was performed bilaterally (right and left lung sites) with a flexible videoendoscope passed through the left or right nasal passage. During lavage of the first lung site, a BALF sample was collected by means of either gentle syringe aspiration or mechanical suction with a pressure-regulated wall-mounted suction pump. The endoscope was then maneuvered into the contralateral lung site, and lavage was performed with the alternate fluid retrieval technique. For each horse, BAL was performed bilaterally once with and once without premedication with NBB (21-day interval). The BALF samples retrieved were evaluated for volume, total cell count, differential cell count, RBC count, and total protein concentration. RESULTS Use of syringe aspiration significantly increased total BALF volume (mean volume increase, 40 mL [approx 7.5% yield]) and decreased total RBC count (mean decrease, 142 cells/μL), compared with use of mechanical suction. The BALF nucleated cell count and differential cell count did not differ between BAL procedures. Use of NBB had no effect on BALF retrieval. CONCLUSIONS AND CLINICAL RELEVANCE Results indicated that retrieval of BALF by syringe aspiration may increase yield and reduce barotrauma in horses at increased risk of bronchoconstriction and bronchiolar collapse. Further studies to determine the usefulness of NBB and other bronchodilators during BAL procedures in horses are warranted.

Comparison of Tracheal Wash and Bronchoalveolar Lavage Cytology in 154 Horses With and Without Respiratory Signs in a Referral Hospital Over 2009-2015

Most equine lower respiratory diseases present as increased airway neutrophilia, which can be detected in tracheal wash (TW) or bronchoalveolar lavage fluid (BALF) cytology samples. The aim was to compare the TW and BALF results in a population of client-owned horses with and without clinical respiratory disease signs. A secondary aim was to determine the sensitivity (Se) and specificity (Sp) of TW and BALF neutrophilia in detecting respiratory disease. The cutoff values for neutrophils were also evaluated. Retrospective data from 154 horses of various breeds that had been subject to both TW and bronchoalveolar lavage (BAL) sampling at rest during 2009−2015 were used. The horses were divided into three groups based on the presenting signs, physical examination, and endoscopy mucus score. Neutrophil counts of >20% in TW and >5% in BAL were considered abnormal. Cytology results between groups, correlations between TW and BALF cell types, and tracheal mucus score were analyzed. Two graph receiving operating characteristic (ROC) curves of the neutrophil percentage values of TW and BALF were created to determine the optimal cutoff values and to calculate the diagnostic Se and Sp for diagnosing airway inflammation in horses with and without clinical respiratory signs. The Se and Sp of TW and BALF neutrophil percentages were further estimated using a two-test one-population Bayesian latent class model. The two tests showed substantial agreement, and only 17.5% of the horses were classified differently (healthy vs. diseased). The neutrophil percentage was found to correlate between TW and BALF. The Se and Sp of TW were generally higher than for BAL when estimated with area under the curve or Bayesian model. Cutoff values of 17.7% for TW and 7% for BALF were indicated by the ROCs. We conclude that TW is a more sensitive and specific method in our patient population. We suggest that the current neutrophil cutoff values of 20% for TW and 5% for BALF would still be appropriate to use in clinical diagnosis of airway inflammation. However, further studies with other cell types and in other populations are warranted to determine the best sampling method for individual horses.

Prevalence of Equine Hepacivirus Infections in France and Evidence for Two Viral Subtypes Circulating Worldwide

Like hepatitis C virus (HCV) in humans, the newly identified equine hepacivirus (NPHV) displays a predominating liver tropism that may evolve into chronic infections. The genomes of the two viruses share several organizational and functional features and are phylogenetically closest amongst the Hepacivirus genus. A limited amount of data is available regarding the spread of hepacivirus infections in horses. In this study, we asked whether in a more representative sample the prevalence and distribution of NPHV infections in France would resemble that reported so far in other countries. A total of 1033 horses sera from stud farms throughout France were analysed by qRT-PCR to determine the prevalence of ongoing NPHV infections and viral loads; in positive samples, partial sequences of NPHV's genome (5'UTR, NS3 and NS5B genes) were determined. Serum concentrations of biliary acids, glutamate dehydrogenase (GLDH) and L-gamma-glutamyl transferase (γ-GT) were measured for most horses. We detected NPHV infections in 6.2% of the horses, a prevalence that reached 8.3% in thoroughbreds and was significantly higher than in other breeds. The presence of circulating virus was neither significantly associated with biological disturbances nor with clinical hepatic impairment. Our phylogenetic analysis was based on both neighbour-joining and maximum-likelihood approaches. Its result shows that, like almost everywhere else in the world so far, two major groups of NPHV strains infect French domestic horses. Based on genetic distances, we propose a classification into two separate NPHV subtypes. Viral loads in the serum of horses infected by the main subtype were, in average, four times higher than in those infected by the second subtype. We hypothesize that amino acid substitutions in the palm domain of NS5B between NPHV subtypes could underlie viral phenotypes that explain this result.

Exercise-induced pulmonary hemorrhage: where are we now?

As the Thoroughbreds race for the final stretch, 44 hooves flash and thunder creating a cacophony of tortured air and turf. Orchestrated by selective breeding for physiology and biomechanics, expressed as speed, the millennia-old symphony of man and beast reaches its climax. At nearly 73 kilometers per hour (45 mph) over half a ton of flesh and bone dwarfs its limpet-like jockey as, eyes wild and nostrils flaring, their necks stretch for glory. Beneath each resplendent livery-adorned, latherin-splattered coat hides a monstrous heart trilling at 4 beats per second, and each minute, driving over 400 L (105 gallons) of oxygen-rich blood from lungs to muscles. Matching breath to stride frequency, those lungs will inhale 16 L (4 gallons) of air each stride moving >1,000 L/min in and out of each nostril - and yet failing. Engorged with blood and stretched to breaking point, those lungs can no longer redden the arterial blood but leave it dusky and cyanotic. Their exquisitely thin blood-gas barrier, a mere 10.5 μm thick (1/50,000 of an inch), ruptures, and red cells invade the lungs. After the race is won and lost, long after the frenetic crowd has quieted and gone, that blood will clog and inflame the airways. For a few horses, those who bleed extensively, it will overflow their lungs and spray from their nostrils incarnadining the walls of their stall: a horrifically poignant canvas that strikes at horse racing's very core. That exercise-induced pulmonary hemorrhage (EIPH) occurs is a medical and physiological reality. That every reasonable exigency is not taken to reduce/prevent it would be a travesty. This review is not intended to provide an exhaustive coverage of EIPH for which the reader is referred to recent reviews, rather, after a brief reminder of its physiologic and pathologic bases, focus is brought on the latest developments in EIPH discovery as this informs state-of-the-art knowledge, the implementation of that knowledge and recommendations for future research and treatment.

Inflammatory Airway Disease of Horses--Revised Consensus Statement

The purpose of this manuscript is to revise and update the previous consensus statement on inflammatory airway disease (IAD) in horses. Since 2007, a large number of scientific articles have been published on the topic and these new findings have led to a significant evolution of our understanding of IAD.

Cytokine concentrations in bronchoalveolar lavage fluid from horses with neutrophilic inflammatory airway disease

Background

Multiple cytological patterns occur in bronchoalveolar lavage fluid (BALF) of horses with inflammatory airway disease (IAD). Only few data on BALF cytokine profiles are available for horses with IAD, and are limited to mRNA expression.

Hypothesis/Objective

Cytological profiles of IAD are associated with different BALF immunological pathways. To investigate BALF cytokine concentrations in a large number of horses with neutrophilic IAD.

Animals

One hundred and thirty‐eight client‐owned Standardbred racehorses in active training.

Methods

Prospective observational study. BALF samples were obtained from left and right lungs. Interleukin (IL)‐4, interferon (IFN)‐γ, and tumor necrosis factor (TNF)‐α concentrations were determined by ELISA.

Results

Fourteen horses had normal BALF cytological profiles and 56 exhibited evidence of bilateral neutrophilic IAD. Twenty‐four horses showed BALF with, respectively, IAD‐ and CTL consistent cytology and were excluded; as were 44 horses because of evidence of pulmonary hemorrhage. TNF‐α (56 ± 115 pg/mL; P = .034) and IFN‐γ concentrations (104 ± 247 pg/mL; P = .044) were significantly higher for IAD horses, compared with controls (respectively 19 ± 41 and 80 ± 116 pg/mL). Horses with ‘neutrophil’ subtype had significantly higher IFN‐γ concentrations (110 ± 154 pg/mL), than ‘neutrophil/metachromatic’ (56 ± 54 pg/mL; P = .028) and ‘neutrophil/metachromatic/eosinophil’ subtypes (44 ± 23 pg/mL; P = .012).

Conclusions and Clinical Importance

Cytokine concentrations in BALF suggested that neutrophilic IAD is associated with activation of the innate immune system and a possible T‐helper (Th)‐1 polarized response. This study also suggested that immunological pathways vary according to cytological IAD subtypes.