Equine Lower Respiratory Tract Disorders PDF 2024/25

VMS3010 2024/25 EQUINE LOWER R E S P I R AT O R Y T R A C T DISORDERS DR NEZA MRZDOVNIK DVM MRCVS PHD LECTURER IN VETERINARY EDUCATION & TRAINING LEARNING OBJECTIVES Be able to: 1) Develop an understanding of the common conditions affecting the lower r...

VMS3010 2024/25 EQUINE LOWER R E S P I R AT O R Y T R A C T DISORDERS DR NEZA MRZDOVNIK DVM MRCVS PHD LECTURER IN VETERINARY EDUCATION & TRAINING LEARNING OBJECTIVES Be able to: 1) Develop an understanding of the common conditions affecting the lower respiratory tract of the horse. 2) Describe the different diagnostic modalities used to investigate respiratory conditions in horses and understand the benefits of each. 3) Outline the diagnosis, treatment and control of infectious respiratory disease in horse. 2 S I G N S O F A I RWAY D I S EA S E I N H O RS ES Cough Nasal discharge Abnormal breathing pattern/sounds 3 A B N O R M A L B R E AT H I N G PAT T E R N I N H O R S E S Normal breathing pattern in horses? → Normal respiration in the resting adult horse is slow (8–16 breaths/min) with minimal chest or abdominal wall movement N/B: Ponies may have a → Costo-abdominal (Slight movement of costal arch, followed by the slight end- slightly higher expiratory abdominal lift) resting respiratory rate (up to 20 → Slight movement of the nostrils. breaths/min). Abnormal: → The increased rate & depth, → and cahnged pattern of breathing should be noted, → as should any abnormal sounds associated with breathing 4  Prolonged and laboured expiration = exaggeration of the biphasic expiratory phase with Exaggerated expiratory contraction of the increased incorporation of the abdominal muscles → abdominal muscles producing an obvious biphasic or double expiratory Heave line in chronic cases Expiratory dyspnoea lift: ‘heave’ Rhythmic pumping of the anus Dilation of the nares throughout the respiratory Typical of small airway obstruction. cycle Extension of the head and neck = associated with a stertorous or stridorous noise during inspiration Prolonged and laboured inspiration Increased respiratory effort Indicative of upper airway obstruction. Dilation of the nares throughout the respiratory Inspiratory dyspnoea cycle Extension of the head and neck Occasionally, inspiratory dyspnoea may occur with severe restrictive lung diseases (e.g. pneumonia, interstitial disease, pneumothorax, rib fracture). Usually with tachypnoea. Combined inspiratory & = Suggestive of severe upper or lower airway Rapid and shallow breathing. expiratory dyspnoea obstruction, diffuse pulmonary disease or pleural disease. 5 U N D E R S TA N D I N G A B N O R M A L A U S C U LTAT I O N S O U N D S – C L I N I C A L I M P L I C AT I O N S Normal lung sounds Abnormal lung sounds Lung auscultation = vary depending on the body condition and INCREASED AUDIBILITY of normal breath sounds occurs with depth of breathing. hyperventilation and occurs focally over areas of consolidated lung tissue. → In fat horses, airflow sounds may be difficult to appreciate → can be accentuated → A generalized increase in the intensity of airflow sounds by using a re-breathing bag! is suggestive of lower airway disease such as SEA (= inflamed airways) © Equine Medicine, Surgery and Reproduction = most intense over the distal cervical REDUCED AUDIBILITY of normal lung sounds is common in trachea & at the area around the carina obese horses. Regional loss of lung sounds also occurs when © Color Atlas of Equine Pathology the pleural cavity contains air, fluid or abnormal tissue. → May be difficult to perceive at the lung periphery. → A localized absence of sounds may indicate a pulmonary or pleural abscess/tumour/mass. → Absence of sounds in the ventral thorax (may be bilateral) suggests a pleural effusion. → Absence of sounds in the dorsal thorax is suggestive of Inflamed trachea Normal trachea pneumothorax. ADVENTITIOUS SOUNDS: Adventitious breath/lung sounds = crackles abnormal sounds resulting from wheezes unusual airflow through the lungs. pleural friction sounds 6 ADVENTITIOUS SOUNDS CRACKLES WHEEZES PLEURAL FRICTION = ‘popping’ open of airways that were = musical notes produced by air flowing = ‘crunching/creaking’ sounds due to the closed during expiration; through narrowed airways rubbing together of inflamed pleural = ‘bubbling and crackling’ sounds caused → SEA, bronchopneumonia surfaces by air bubbling through excessive mucus → inflamed surfaces lose lubrication! in the airways → Pleuritis → SEA,acute obstructive pulmonary disease, pulmonary oedema © Color Atlas of Equine Pathology Inflamed trachea Normal trachea 7 E Q U I N E L O W E R R E S P I R AT O R Y T R A C T DISORDERS = ‘Mild/moderate equine asthma’ (MEA) Bacterial: = Parasitic: ‘Severe equine asthma’ (SEA) Viral: ©Equine Internal Medicine, 4th Ed 8 Diseases of the airways Asthma → Mild (also IAD = Inflammatory Airway Disease) → Severe (also RAO = Recurrent Airway Obstruction) Infectious airway diseases Diseases of the lung tissues Pneumonia → Bacterial → Sterile (Chronic Interstitial Inflammatory Infiltrates/pneumonitis) Equine Multinodular Pulmonary Fibrosis Neoplasia Other Exercise Induced Pulmonary Haemorrhage Congestive Heart Failure (pulmonary oedema) N.Mrzdovnik personal archive ©Equine Internal Medicine, 4th Edition 9 EQUINE ASTHMA Severe Equine Asthma (‘SEA’) Healthy horse → Equine Pasture Asthma (‘EPA’) Mild/moderate Equine Asthma (‘MEA’) Asthmatic horse © Bullone & Lavoie 2020 © Bullone & Lavoie 2020 10 MILD EQUINE ASTHMA (MEA) Clinical picture: Common in young performance horses Any age – young > old Subacute-chronic presentation poor performance Intermittent cough (only 38% of cases?) Nasal discharge? Lung auscultation – normal sounds Causation: Poor ventilation Dusty hay / bedding NH3,H2S etc,…. Infectious agents? 11 SEVERE EQUINE ASTHMA (SEA) Clinical picture: Essentially, SEA differs from MEA primarily in that Common in mature horses and ponies clinical signs of difficulty breathing are already → (usually > 7 years old) present AT REST in SEA. Subacute-chronic presentation Abdominal effort/nostril flaring Coughing “Wheezes and crackles” ©Boehringer Causation: Poor ventilation: → Dusty hay/straw bedding (moulds) → NH3, H2S,…. Seasonal environmental allergens? Pasture asthma 12 S E V E R E EQ U I N E A S T H M A - PAT H O P H Y S I O LO G Y 1. Airway hyperresponsiveness 2. Inflammation → Airway wall thickening Healthy horse → Neutrophil – rich airway secretions 3. Increased mucus production 4. Bronchospasm 5. Airway remodeling N.Mrzdovnik personal archive Asthmatic horse Key characteristic: REVERSIBLE AIRWAY OBSTRUCTION © Bullone & Lavoie 2020 13 N.Mrzdovnik personal archive 14  S E V E R E EQ U I N E A S T H M A – T R E AT M E N T A N D MANAGEMENT AIR HYGIENE – ‘DUST-FREE’ MANAGEMENT → Hay, straw, muck heap, general dust, dry cereals, Environmental neighbouring boxes (!),… No treatment will work if control the cause is still present – Summertime cases? air hygiene! → Pollens, moulds, pollutants,…? 1. Glucocorticoids → Systemic (Dexamethasone, Prednisolone) / Inhaled (Ciclesonide, Budesonide, Beclomethasone, Fluticasone) 2. β2 adrenergic agonists (Clenbuterol, Salbutamol, Salmeterol) Medical treatment 3. Muscarinic antagonists (Systemic: Hyoscine/butylscopolamine, Atropine; Inhaled: Ipratropium) 4. Furosemide E N V I R O N M E N TA L ( ‘ D U S T - F R E E ’ ) C O N T R O L 1. Manage from pasture - with no access to hay or straw. 2. Minimize dust levels in stable: Bedding: → shavings/shredded paper/peat/synthetic bedding/rubber mats/sand, etc. → maintain clean, dry bed (avoid deep litter). Ventilation: ensure adequate ventilation rates. Ensure horse is in a separate airspace (or else all horses in the same airspace must be managed under similar dust-free conditions). Avoid overhead lofts. Keep muck heap as far away from the stable as possible. Horse should be out of the stable when it is mucked out (and for 30 minutes afterwards). Feeding: If possible, feed an alternative to hay, e.g. ‘complete diet’ nuts, silage, vacuum-packed hays. → If hay is to be fed, it should be good quality and steamed or thoroughly soaked prior to feeding. → Soaking may decrease the nutritional content of the hay. Soaked hay should be fed in small quantities so it doesn’t dry out before it is consumed. Consider use of dust extractor in the box. 16 ©Equine Internal Medicine, 4th Edition  Link to the article Link to the article ‘RDC’ = respirable dust concentration = defined as the portion that is of a sufficiently small aerodynamic size (usually with Link to the article a diameter of old Acute presentation Cough/nasal discharge? Fever? Dull / inappetent? Causation: Viral: EHV, EIV, ERV, (EVA) Bacterial: Streptococci, Actinobacillus, Rhodococcus etc. Parasitic: Dictyocaulus ©Equine Internal Medicine, 4th Edition ©Equine Internal Medicine, 4th Edition 20 Equine Herpesvirus (EHV) all over the world. Of the four main types, EHV-1 and EHV-4 are the most common in the UK. EHV-1: can cause signs of respiratory disease in young horses (runny nose, coughing, raised temperature), abortion in pregnant mares (usually later in pregnancy and sometimes in large outbreaks involving multiple mares) and sometimes paralysis in horses (of all ages). EHV-4: minimal effect on breathing and can occasionally cause abortion EHV-5: unusual type of lung condition in adult horses Equine Influenza virus (EIV) Most common in horses commingled under stressful conditions Viral spread: through aerosolization of viral particles + fomites short incubation period (1 to 3 days) high fever, depression, paroxysmal and persistent coughing, nasal discharge (serous → ©Colour atlas of equine pathology mucopurulent), submandibular lymphadenopathy, myositis, anorexia Horses with influenza = at risk of secondary bacterial infection that may progress to bronchopneumonia and/or pleuropneumonia 21 Bacterial pneumonia → Initial colonization = primary airways Younger > older horses. (bronchitis). → Disease progression - extension beyond the airways to the surrounding Events that lead to suppressed endogenous immunity pulmonary parenchyma may result in bacterial colonization of the lower (bronchopneumonia). respiratory tract. ! → Further disease dissolution = most → A primary viral upper respiratory tract infection advanced progression of bacterial → General anesthesia colonization with extension to the → Long-distance transport pleural space and associated structures (pleuropneumonia). Bacterial pathogens isolated from the lower respiratory tract: opportunistic, environmental, or commensal organisms that are unable to initiate primary invasion. → The most frequently isolated organism from horses suffering from primary pneumonia is S. equi subsp. zooepidemicus. Treatment: Broad-spectrum antibiotic + general supportive care → When disease is severe or chronic or involves marked ©Colour atlas of equine pathology immunosuppression: guarded prognosis! 22 Rhodococcus equi Gram-positive, intracellular bacteria → causes chronic suppurative bronchopneumonia with abscessation Foals: 1–5 months of age. Clinical signs: mild and nonspecific early in the course of disease become more pronounced as pneumonia progresses cough, fever, lethargy, and increased respiratory effort – respiratory distress. Diagnosis: → culture of R. equi and identification via PCR (from transtracheal wash sample). → radiology and ultrasonography ©Merck Veterinary Manual Recommended treatment for foals with confirmed R equi pneumonia: → prolonged antimicrobial treatment. → oxygen therapy, steroids, NSAIDs. Prognosis: guarded. 23 ©Colour atlas of equine pathology PLEUROPNEUMONIA Will have separate lecture on pleural diseases ©Equine Internal Medicine, 4th Edition 24  INTERSTITIAL PNEUMONIA / CHRONIC INTERSTITIAL PNEUMONITIS Chronic interstitial disease, quite rare → Mycobacterial infections are occasionally recognized. → Other chronic interstitial pneumonias and inflammatory/fibrotic diseases of unknown aetiology also occur → (EHV-5 - Equine Multinodular Pulmonary Fibrosis) Clinical signs: May present with chronic but progressive dyspnoea/tachypnoea, weight loss, fever (persistent or recurrent). Auscultation – harsh lung sounds with variable wheezing and crackling. Diagnosis: 1. History and clinical signs. Lack of response to standard therapy for lower airway diseases. 2. Leukocytosis and hyperfibrinogenaemia. 3. Thoracic radiography – interstitial infiltrate 4. Endoscopy (Bronchoalveolar lavage = BAL) Treatment: There is no treatment. → Long-term antiinflammatory drugs or corticosteroids may be beneficial in chronic interstitial inflammatory diseases. → Acyclovir or valacyclovir may be helpful in early cases of EHV-5 infection (equine multinodular pulmonary fibrosis). 25  EQ U I N E M U LT I N O D U L A R P U L M O N A RY F I B RO S I S Uncommon/rare Weight loss, fever, respiratory distress Link to the article Can affect any age Diagnosed by radiography/ultrasound/ biopsy Commonly associated with EHV-5 infection (relevance?) Might respond to glucocorticoids (or vanciclovir?) if treated early ©Equine Internal Medicine, 4th Edition ©Colour atlas of equine pathology 26 THORACIC NEOPLASIA Primary lung tumours (5-10% of thoracic neoplasms): ©Colour atlas of equine pathology Granular cell tumour (myoblastoma) → By far the commonest primary tumour in horses. → Average age 13 y, but can be quite young (eg, 6 yo). → May cause chronic coughing, tachypnoea and weight loss. → Endoscopy/radiography: masses grow into bronchi and bronchioles. ©Colour atlas of equine pathology → Locally invasive but do not metastasise. → A benign and slow-growing tumour but may: o cause persistent coughing o block bronchus and cause focal pneumonia 27 THORACIC NEOPLASIA Metastatic tumours (>90% of thoracic neoplasms) Mediastinal lymphoma = commonest → Mature to elderly horses → Weight loss, lethargy, anorexia, brisket oedema, cough, respiratory effort, (lymphadenopathy) → Ultrasonography: often have non-septic pleural effusion → May see masses with radiography/ultrasound Other metastatic tumour types include: → Hemangiosarcoma → Adenocarcinoma → Melanoma → Squamous cell carcinoma ©Colour atlas of equine pathology 28 EXERCISE-INDUCED PULMONARY H A E M O R R H A G E ( ‘ E I P H ’, ‘ B L E E D E R S ’ ) CONSEQUENCES OF EQUINE ADAPTATION TO SUPREME ATHLETICISM: High pulmonary capillary pressure (~ 95 mmHg) is required to feed blood into the high pressure left atrium (~ 70 mmHg). Alveolar-capillary barrier further compromised by: - Highly negative airway pressures sucking air into alveoli; - Airway diseases → even more negative inspiratory pressures; → Eg: laryngeal hemiplegia, mild asthma - Arrythmias → occasional delayed beats with surges in cardiac output; → Eg: Atrial fibrillation … Leading to inevitable failure of capillary walls 29 EIPH: = Bleeding from the caudodorsal lung lobes during exercise Incidence depends on many risk factors Intensity/duration of exercise Fitness More starts/older Harder tracks (faster) Cooler temperatures Horses are less likely to bleed if they are…: Disease: → Lower respiratory – e.g. mild asthma Fitter → Upper respiratory – e.g.laryngeal hemiplegia Lighter → Cardiac – e.g. atrial fibrillation Have healthy, non-inflamed airways Have no respiratory obstructions (upper or lower) Have an even cardiac output (not atrial fibrillation) 30 EXERCISE – INDUCED PULMONARY HAEMORRHAGE (EIPH, ‘BLEEDERS’) Prevalence in racehorses Epistaxis 0.15% Tracheal endoscopy 26 - 77% Repeated endoscopy 82 - 95% Bronchoalveolar lavage 100% ©Colour atlas of equine pathology ©Colour atlas of equine pathology 31 CONGESTIVE HEART FAILURE Mitral insufficiency → pulmonary hypertension → oedema Rare in horses Likely to have tachycardia and severe left sided systolic murmur Might respond to digoxin/furosemide in short-term? Try benazepril? Pulmonary oedema – typical white frothy nasal discharge ©Equine Medicine, Surgery and Reproduction; 2nd ed 32 DIAGNOSTIC APPROACHES FOR LOWER T R A C T R E S P I R AT O R Y D I S O R D E R S I N HORSES Always requires a multifaceted approach! 1. History/signalment 2. Clinical signs 3. Blood tests 4. Endoscopy findings 5. Airway cytology 6. Airway microbiology 33 ©Equine Medicine, Surgery and Reproduction; 2nd Ed. C L I N I C A L E X A M I N AT I O N 1. Rectal temperature ? Normal? ? Abnormal? 2. Nasal discharge → Quality & Quantity! → may be swallowed! 3. Lymph nodes 4. Laryngeal squeezing → cough? 5. Auscultation → Tracheal sump – mucus accumulation → Lung fields ? crackles ? wheezes Why called ? silence ‘rebreathing’? → Rebreathing bag o Enhances sounds o Does it induce coughing? o Is it always safe? → Heart (cardiac failure rare but possible)) 34 35 C L I N I C A L D I F F E R E N T I AT I O N O F A I R WAY DISEASES 36 H A E M ATO LO GY / A C U T E P H A S E P R OT E I N S Asthma – usually no changes Infectious airway disease → Neutrophilia? → Neutropaenia? → Lymphocytosis? → Monocytosis? → Increased fibrinogen? → Increased SAA? 37 V I S UA L A S S ES S M E N T O F A I RWAY - E N D O S C O P Y LYMPHOID HYPERPLASIA May reflect infectious challenge What is normal/acceptable for age? 38 V I S UA L A S S ES S M E N T O F A I RWAY ≤ GRADE 1/5 can be found in normal horses ≥ GRADE 2/5 associated with poor performance in TBs 39 ©Gerber et al. 2004. Endoscopic scoring of mucus quantity and quality TW VS BAL - DIAGNOSTIC VALUE TW = tracheal wash → Not a question of either/or! BAL = bronchoalveolar lavage TW BAL Bacteriology Good if careful No good Wide reference ranges Precise reference ranges Poor preservation Excellent cellular identification Cytology Samples whole lung Samples small lung segment Poor association with Strong association with performance performance Poor association with one another 40 TW AND BAL CYTOLOGY IN DISEASE Infectious airway disease MEA SEA TW BAL TW BAL TW BAL Moderate to x Mild to moderate neutrophilic Moderate to severe severe inflammation neutrophilic inflammation neutrophilic inflammation Sometimes eosinophils Rarely eosinophils Sometimes mast cells Rarely mast cells Sometimes mixed Curschmann’s spirals? inflammatory cells 41 REFERENCES E. Davis (2018). Disorders of the Respiratory System. In S. M. Reed, W. M. Bayly, & D. C. Sellon (Eds.), Equine internal medicine (4th ed., pp. 313 – 386). Elsevier. Mair, T. S., & Rush, B. R. (2012). Lower respiratory tract. In Equine Medicine, Surgery and Reproduction (2nd ed., pp. 111- 132). Elsevier. Buergelt, C. D., & Del Piero, F. (2013). Color atlas of equine pathology. Wiley Blackwell. Bullone M, Lavoie JP. The equine asthma model of airway remodeling: from a veterinary to a human perspective. Cell Tissue Res. 2020 May;380(2):223-236. doi: 10.1007/s00441-019-03117-4. Couëtil, L.L., Cardwell, J.M., Gerber, V., Lavoie, J.P., Léguillette, R. and Richard, E.A., 2016. Inflammatory airway disease of horses—revised consensus statement. Journal of veterinary internal medicine, 30(2), pp.503-515. Couetil L, Cardwell JM, Leguillette R, Mazan M, Richard E, Bienzle D, Bullone M, Gerber V, Ivester K, Lavoie JP, Martin J, Moran G, Niedźwiedź A, Pusterla N, Swiderski C. Equine Asthma: Current Understanding and Future Directions. Front Vet Sci. 2020 Jul 30;7:450. doi: 10.3389/fvets.2020.00450. Dunkel, B. (2024) Respiratory emergencies in adult horses. Equine Veterinary Education, 00, 1–10. Available from: https://doi.org/10.1111/eve.13976 GERBER, V., STRAUB, R., MARTI, E., HAUPTMAN, J., HERHOLZ, C., KING, M., IMHOF, A., TAHON, L. and ROBINSON, N.E. (2004), Endoscopic scoring of mucus quantity and quality: observer and horse variance and relationship to inflammation, mucus viscoelasticity and volume. Equine Veterinary Journal, 36: 576-582. https://doi.org/10.2746/0425164044864525 Gerber V, Lindberg A, Berney C, Robinson NE. Airway mucus in recurrent airway obstruction--short-term response to environmental challenge. J Vet Intern Med. 2004 Jan-Feb;18(1):92-7. doi: 10.1892/0891-6640(2004)182.0.co;2. PMID: 14765737. 42  WITH ACKNOWLEDGEMENT AND THANKS TO ANDY D U R H A M FO R S O M E O F T H E S L I D ES’ M AT E R I A L Presentation Name | Date | Version 0.0 43