Inflammatory Airway Disease Flashcards
IAD and RAO represent a spectrum of chronic inflamm disease of the airways in horses resembling human asthma in many respects. It should not be interpreted as a disease continuum, in which horses with IAD necessarily develop RAO over time. What are the main differences between the two?
Age of onset - IAD can be seen at any age; RAO is usually older than 7 years
IAD has no increased resp effort at rest
What are some exclusion criteria for IAD?
Evidence of systemic signs of infection such as anorexia, lethargy, fever, hematologic abnormalities compatible with infection
Increased respiratory at rest
What contributes to the pathogenesis of IAD?
Noninfectious agents are likely central. High burdens of aerosolized particles and gases in a cumulative manner.
The presences of what cytokines in a BALF suggest a role for aeroallergens?
High eosinophil or mast cell counts and Th-2 cytokines such as IL-4 and IL-5
Metachromatic cells in IAD vs neutrophiic IAD are assoc. with what?
Metachromatic - airway hypersensitivity and subclinical pulmonary obstruction
Neutrophilic - cough and presence of tracheal mucus
Three criteria for diagnosis of IAD.
- Presence of clinical signs of lower airway disease (poor performance, cough)
- Documentation of lower airway inflammation based on excess mucus on endoscopy, BALF cytology or abnormal lung function
- Exclusion of severe equine asthma (RAO/heaves)
Describe the different grades for quantifying mucus accumulation in the trachea.
Grade 0 - no visible mucus
Grade 1 - single to multiple small blobs of mucus
Grade 2 - larger but nonconfluent blobs
Grade 3 - confluent or stream forming mucus
Grade 4 - pool forming mucus
Grade 5 - profuse amounts of mucus
What are BALF cytology results of a healthy horse?
TNCC - = 530 cells/uL
Neutrophils = 5%
Eosinophils = 1 %
Metachromatic cells = 2%
Due to many overlapping characteristics, what is a practical way to discriminate RAO from IAD?
Hay challenge - horses with IAD exposed to moldy hay may exhibit a worsening of coughing and pulmonary neutrophilia, but they do not develop increased respiratory efforts or lung dysfunction at rest, as RAO-affected horses.
List differentials for IAD and how they are ruled out.
RAO - lack of labored breathing at rest permits differentiation; RAO has severe exercise intolerance and pronounced BALF neutrophilia
Viral infection - more severe clinical signs referable to the respiratory tract as well as more severe clinical signs
Bacterial bronchitis and bronchopneumonia - weak evidence assoc. IAD and Strep. zooepidemicus; typically severe infections have systemic clinical signs
Lungworm infection - Dictyocaulus arnfieldi, eosinophilic inflamm is typically more severe and persistent in parasitic pneumonitis
EIPH - assoc with macrophagic bronchiolitis and fibrosis, potential assoc. between IAD and EIPH is controversial
Neoplasia - uncommon in horses, further diagnostics warranted
Upper airway diseases - presence of abnormal breathing soudns at rest or during exercise (strider, stertor), and the absence of mucopurulent secretions and inflammation in the lower airways should help differentiate these conditions from IAD
List some viral infections that could be listed as differential diagnoses for IAD.
Equine influenza Equine alpha-herpesvirus (EHV-1) EHV-4 Equine rhinitis A and B Equine adenovirus-1 EHV-5
How important are bronchodilators for treatment of IAD?
The degree of bronchodilators is too low to induce clinical signs at rest and has not been well documented at rest or during exercise.
Treatment should be done in conjunction with measures to decrease exposure to environmental dust so that exposure of lower airways to particulates is not increased.
Other than corticosteroids, systemic/inhaled, what are some novel treatments for IAD?
Mast cells stabilizers - sodium cromoglycate, improve clinical signs and decreases bronchial hyperresponsiveness
Low-dose interferon alpha - reduced neutrophilic inflamm of racehorses with IAD and reduced likelihood of relapse
Nanoparticles of cytosine-phosphate-guanosine oligonucleotides - induce a Th2/Th-1 shift, shown to decrease neutrophil percentages in TW
Polyunsaturated omega-3 fatty acids - Docosahexaenoic acid was shown, in addition to switching horses to a low-dust diet, was shown to provide more rapid improvement
Which is better for IAD horses, hay in a net or on the ground?
Hay in a net will result in greater than 4-fold increased exposure to respirable dust in the breathing zone, compared to feeding the same hay on the ground, regardless of background level in the stable.
