Equine Respiratory Diseases Flashcards
1
Q
Describe the anatomy of the equine guttural pouches.
A
- Paired air-filled diverticula of the eustachian tubes
- Divided into medial (2/3) and lateral compartments (1/3) by the stylohyoid bone
- Cranial nerves contained in the lateral compartment = 7, 9, 10, 11, & 12
- Also within the guttural pouch: cranial sympathetic trunk, internal carotid artery, and branches of the external carotid artery
- NOT a sterile environment
2
Q
Explain the relationship of the guttural pouches to surrounding important structures
A
- Ventral to the atlas, dorsocaudal to the pharynx, and rostrodorsal to the retropharyngeal lymph nodes
- Viborg’s triangle
o Tendon of the sternomandibular muscle
o Linguofacial vein
o Caudal boarder of the vertical ramus of the mandible
3
Q
What are the 4 equine respiratory viruses?
A
Influenza A
EHV 1,4 & 2,5
EVA
Rhinovirus A & B
4
Q
What is the incubation period of each of the four equine respiratory viruses?
A
Influenza A: 1-3 days
EHV 1,4 & 2,5: 1-3 days
EVA: 3-14 days
Rhinovirus A&B: 3-8 days
5
Q
What are the clinical signs associated with respiratory viral diseases?
A
High fever (up to 106)
Dry cough
Submandibular lymphadenopathy
Serous nasal discharge
Rapid spread among susceptible animals
Anorexia, depression
Secondary pneumonia
6
Q
How do you diagnose respiratory viral diseases?
A
History and clinical signs
CBC- leukopenia, lymphopenia, anemia
PCR
Virus isolation
Antibody detection (paired samples)
Not Practical: Virus isolation, Antibody detection (paired samples)
7
Q
What is the diagnostic of choice for respiratory viral diseases?
A
PCR-will tell you which virus horse has, there are panels
The four most infectious and most common: Flu, EHV 1&4 , and strep equi. Then you can get expanded panels with other ones like rhinovirus and EVA.
8
Q
What is the treatment for respiratory viral diseases?
A
Treatment is symptomatic.
Make sure theyre in a clean, well-ventilated, stress-free environment
Monitor for secondary bacterial infections
NSAIDS
Antiviral drugs (none are really known to be good)
REST –> 1 week for every day of fever and a minimum of 3 weeks
9
Q
What are some complications of respiratory viral diseases?
A
Bacterial infections, Pneumonia, Predisposes horse to asthma and/or EIPH, Pleuritis, Bronchitis, sinusitis, pharyngitis
Laryngeal hemiplegia
Pharygeal collapse
Soft palate paresis
10
Q
How do you prevent Influenza?
A
IN or IM vaccine every 6 months, booster 1-2 weeks before potential exposure
11
Q
How do you prevent EHV-1,4?
A
IM vaccine q 6 months
12
Q
How do you prevent EVA?
A
Identification of carrier stallions –> its testicular dependent so stallions can be chronic carriers
Vaccination
13
Q
How do you prevent Rhinovirus?
A
IM vaccine annually
14
Q
How should you perform a clinical exam of the equine lower respiratory tract?
A
Observation from a distance
Close-up exam
Auscultation of lung fields–> at rest and rebreathing exam
* Auscultate trachea too because sometimes you can hear stuff in there too
Percussion
15
Q
what is epistaxis?
A
Blood at the external nares
16
Q
Define Exercise Induced Pulmonary Hemorrhage.
A
Strenuous exercise associated with exudation of RBC from the pulmonary vasculature into the alveoli and airways of the caudodorsal lung segments
17
Q
T/F EIPH always causes epistaxis.
A
False, if a horse has epistaxis it doesnt always mean its EIPH
18
Q
What is the origin of epistaxis?
A
Nasal cavity, Paranasal sinuses, guttural pouch, pharynx, larynx, oral cavity, lungs
19
Q
What are some differentials for epistaxis?
A
o Nasal trauma
o Ethmoid hematoma
o Guttural pouch mycosis
o Chronic pulmonary disease
o Upper respiratory tract neoplasia
o Thrombocytopenia
o Pulmonary hemorrhage
o Many others!
20
Q
What are some differentials for pulmonary hemorrhage?
A
o EIPH
o Pulmonary abscess
o Fungal granuloma
o Trauma
o Pneumonia
o Foreign body
o Neoplasia
21
Q
What is the overall incidence of EIPH and epistaxis?
A
Overall incidence ~47%
Epistaxis ~4%
Increases with age
22
Q
What horses are affected by EIPH?
A
Steeplechasers>Flat racers
* Bc steeplechasers have greater chance of developing pulmonary hemorrhage when hitting ground
Females vs males –> Filly (young female horse) is overrepresented compared to geldings (castrated male)
Shorter races of higher intensity
23
Q
T/F A horse that is not used for intense riding and exercise is at a high risk of developing EIPH.
A
FALSE
24
Q
EIPH Pathogenesis 1: A mild infectious respiratory disease/chronic pulmonary disease/inflammatory airway disease leads to…
A
Intrathoracic airway obstruction resulting in negative alveolar pressure (increased pressure in alveoli) –> then hemorrhage
Basically ventilation abnormalities caused by small airway disease
Low evidence for this theory
25
EIPH Pathogenesis 2: Visceral constraint on the diaphragm due to pressure from the abdominal viscera leads to..
* Increase in mechanical forces developing in dorsal thorax then
* Parenchymal tearing and rupture of capillaries during inspiration
* Then Hemorrhage !!
26
EIPH Pathogenesis 3: Pulmonary hypertension
* This causes bleeding into the airway for a number of reasons
* It may result from high CO, lack of pulmonary vasodilation, and increased blood viscosity during exercise
* All this leads to stress failure of the pulmonary capillaries
* Then Hemorrhage
27
What are the clinical signs of EIPH?
Epistaxis FOLLOWING exercise (only a small #)
Exercise intolerance
Repeated swallowing during exercise
Labored breathing
Post exercise coughing
No signs at the time of examination
28
How do you diagnose EIPH?
1. History and clinical signs
2. Endoscopic examination --> within 90 min of intense exercise
* detection of frank blood within the trachea
1. BAL or TTW
2. Radiography
29
If we do a BAL or TTW for EIPH what would we see on cytology?
Hemosiderophages--> macrophages that have taken up RBC and broken them down
+erythrocytes
+intact/degenerating neutrophils
+/- intracellular bacteria
30
How do you treat EIPH after a bleeding episode?
Antibiotics if severe hemorrhage
Rest--> month or so but will likely reoccur once exercise resumes
Hyperbaric oxygen
31
How do you prevent EIPH?
Prevention, management and treatment of small airway disease
Appropriate rest during respiratory episode
Nasal strips: decrease alveolar & intrapleural pressures
**we want to open airways, decrease neg pressure, and allow for decreased resistance
32
How can Lasix be used as a prophylactic TX in EIPH?
* It aids in reducing EIPH
* Furosemide
* Administered to >92% of Thoroughbred racehorses on the day of racing in North America (400,000 doses/yr)
* 1mg/kg 4 hours prior to race
* **Does not prevent EIPH, but decreases severity up to 90%**
33
What is the mechanism of lasix when used for EIPH?
Diuretic --> **decreases **body weight --> **decreases **intravascular volume --> attenuation of exercise induced **increase** in pulmonary arterial pressure --> **decreased** incidence of alveolar capillary rupture --> **decreased **hemorrhage
34
What is the definition of pneumonia?
obstructive and restrictive disease of the lung characterized by inflammation and airway reaction to an inciting agent (bacterial, viral, parasitic, or foreign body).
35
What are the etiologic agents that can cause pneumonia in the lower respiratory system of horses?
Infectious: Bacterial, Viral, Fungal
Parasitic: Parascaris, lungworm
Foreign Body
36
What are the most common predisposing factors increasing risk of pneumonia in horses?
* Viral respiratory disease
* Athletic events
* Recent long trailer ride
* Immunologic compromise
* Anesthesia
* Stress
* Pharyngeal / laryngeal dysfunction
* EIPH
37
Why is a long trailer ride a predisposing factor for pneumonia?
Anything over 4 hours increases risk especially if head is tied because now they cannot put their head down to cough and expel material
38
Describe bacterial pneumonia.
* Bacteria are normally only transient contaminants within the lungs.
* The animal’s normal defense mechanisms can be overwhelmed due to: aspirated bacteria which can develop into a bacterial pneumonia or It can also be secondary to a viral disease.
39
What are common gram positive bacteria cultured from pneumonia of adult horses?
o Staphylococcus aureus
o Streptococcus pneumoniae
Streptococcus zooepidemicus --> common to upper airway but can cause problems if theres issues
40
What are common gram negative bacteria cultured from pneumonia of adult horses?
o Escherichia coli
o Klebsiella pneumoniae
o Pasteurella
o Actinobacillus
41
What are common anaerobeic bacteria cultured from pneumonia of adult horses?
o Bacteroides fragilis
o Clostridium spp.
o Fusobacterium
42
What are the clinical signs seen in bacterial pneumonia?
Literally anything, just depends on how bad and how chronic it is
* Fever --> Depression --> Anorexia ---> Exercise intolerance --> Tracheal sounds
* Cough --> Nasal discharge--> Tachypnea / Dyspnea --> Respiratory distress --> Weight loss
43
How do you diagnose bacterial pneumonia?
History and clinical signs
Bloodwork and Blood gas
Endoscopic exam (just to make sure we are missing something in the URT)
TTW/BAL
Cytology and Culture
Radiography & Ultrasound
Auscultation of thorax:
* Crackles- alveoli snapping open, typically on inspiration
* Wheezes- air passing over fluid (musical), typically on expiration but can be on both
* Absence of sounds- due to consolidation or fluid
| THERES MORE !!!!!!!!
44
What would you expect on clin path data in an animal with bacterial pneumonia?
o Hyperfibrinogenemia (most consistent finding) --> inflammation
o Neutrophilia +/- left shift
Neutropenia if its a GRAM NEG infection
o Hyperglobulinemia
45
What do you expect the blood gas analysis to be in bacterial pneumonia?
Acidic pH and hypoxic
Increased CO2 bc lung isnt functioning well enough to take in O2 and get rid of CO2
pHCO3 can be normal to increase --> depends on how chronic the pneumonia is and if it has had time to compensate or not
46
What would you expect to see on a TTW/BAL in a horse with Bacterial Pneumonia?
Degenerative neutrophils
Engulfed/free bacteria
Damaged epithelial cells
47
Difference between TTW and BAL? What would you choose to do for DX of bacterial pneumonia?
TTW- gets lower trachea and global view of the lung, and we miss somethings in the small airways. Its done steriley and can get a culture
BAL- allows us to get the small airways but its not sterile
If were worried about pneumonia --> do TTW because its sensitive and we can get a culture
48
In bacterial pneumonia what would we expect to see on radiography?
increased bronchial and/or interstitial pattern
Air bronchograms
49
What are we looking for on Ultrasound DX in bacterial pneumonia?
Comet tails (or b-lines)
Abscesses
Consolidation
Hepatisation
Pleural fluid
***only will see surface level things, US doesnt penetrate very deep and doesnt pass through air
50
Are comet tails specific for bacterial pneumonia?
NO, non-specific
This could be scar tissue, a tiny little abscess, or inflammation
51
How do you treat bacterial pneumonia?
Primary treatment – directed at the causative agent
Secondary Treatment – directed at response to causative agent
Supportive treatment- directed at the total patient
52
What is the primary treatment for bacterial pneumonia?
* Appropriate antimicrobial treatment ideally based on culture and sensitivity but may be based on knowledge of commonly encountered organisms or on trial and error.
53
For primary treatment for bacterial pneumonia with antibiotics what do we need to consider?
Dose, duration, interval and route.
*** Treatment is often prolonged and should extend 7-10 days past attenuation of clinical signs**
Common microbial agents
Broad vs narrow spectrum
Adverse effects
Frequently monitor clinical signs
54
What are some specific examples of antibiotics used to treat bacterial pneumonia?
o Aminoglycosides --> gram neg
o Beta-lactams (poor penetration systemically)
o Cephalosporins
^^gram pos
o Flouroquinolones
o Macrolides (foals only!!)
o Chloramphenicol
o Tetracyclines--> intracellular bacteria
o Potentiated sulfonamides--> oral 2x a day and commonly used so increased resistance is an issue
o Metronidazole (anaerobes)
55
When do you change primary treatment for bacterial pneumonia?
Temperature spikes after 24-48 hrs
No improvement of clinical signs
Adverse effects occurring --> renal compromine, diarrhea etc.
Lab support indicates resistance
56
What are the goals of secondary treatment in bacterial pneumonia?
1. Reduce and eliminate airway obstruction and undesirable inflammatory reaction
2. Improve alveolar-vascular oxygen exchange
3. Provide immune enhancement (occasionally)
57
# Secondary TX in Bacterial Pneumonia
How do we acheive mucolysis and expectoration in a horse with bacterial pneumonia?
This alter the consistency and quantity of secretion
We can do this by:
- Guaifenesin? not super helpful and not alot of evidence
- Nebulization: hydrates and dilutes (with saline), and you can add things like antibiotics, bronchodilators, DMSO, Acetylcysteine
58
# Secondary TX in Bacterial Pneumonia
What is bronchodilation and what drugs would we use to acheive this in a horse with bacterial pneumonia?
* Relaxation of bronchial smooth muscle to reduce airway obstruction
* B2 agonists- Clenbuterol (oral) or Albuterol (inhalant)
* Anticholinergics- Ipratropium bromide (inhalant)
59
# Secondary TX in Bacterial Pneumonia
What are some other secondary treatments of bacterial pneumonia?
Copage- Mechanical break up and movement of secretions, May be beneficial in the foal but not practical or effective in the adult horse
Anti-inflammatory therapy
Immunologic enhancement--> during an acute episode this may be helpful
Oxygen therapy by insufflation
60
What is some supportive treatment for a bacterial pneumonia horse?
* Rest – critical in the pneumonic patient
* Stress reduction – minimal handling and situations that cause unnecessary stress and anxiety, careful handling and planning
* Nutrition--> dont want them to colic
* Adequate ventilation
* Hydration
**keep them out of dusty environments
61
What are the 4 viral pneumonias that are significant in horses?
EHV-1,4
EHV-5- Equine Multinodular pulmonary fibrosis --> bad, probably exposed to this a long time ago and they had an immune reaction that caused their lungs to fibrose and form nodules, Looks like asthma horse, exercise intolerance, cough, and doesnt respond to typical TX
Equine Influenza virus
Equine Viral Arteritis
62
What are the primary pathogens causing Fungal Pneumonia?
* Blastomyces dermatitidis
* Coccidioides immitis
* Cryptococcus neoformans
* Histoplasma capsulatum
* Aspergillus spp. (opportunist)
* Pneumocystis carinii (opportunist) – CID foals (Arabians)
63
What are the contributory factors leading to fungal pneumonia?
* Exposure to large numbers of mycotic organisms in the environment
* Stabling of horses in a moist environment
* Prolonged administration of antibiotics
* Immunosuppression – CID foals, secondary to disease or drug administration
* Neoplasia
64
What are the clinical signs of fungal pneumonia?
* Chronic cough
* Anorexia
* Weight loss
* Exercise intolerance
* Nasal discharge
* Non-responsive to antibiotics
* Pleural effusion (coccidioidomycosis)
* +/- Tachypnea or respiratory distress
65
What leads us to believe a horse has fungal pneumonia vs bacterial pneumonia?
Initially we assume a horse has bacterial pneumonia because its more common but then it wont respond to antibiotic TX so... fungal pneumonia if all diagostics lead to that
66
How do you diagnose fungal pneumonia in a horse?
TTW
BAL--> hard to interpret
Radiographs
67
What are we looking for on a TTW in a horse with fungal pneumonia?
Degenerative neutrophils, yeast, bacteria
Interpret this with caution because we can get a small # of organisms as contaminants especially if the horse coughed during this
68
What are we looking for on a radiographs in a horse with fungal pneumonia?
Circular masses
Accenturated interstitial pattern
+/- pleural effusion
69
How do you treat fungal pneumonia?
* Long term (10-12 weeks) administration of antifungal medications
- Injectables: Amphotericin B, Nystatin, Natamycin --> have soo many side effects
- Oral: Miconazole, Ketoconazole, Itraconazole, Fluconazole (used the most)
| The drugs are not well absorbed in horses
70
Parascaris is common in what age of horses?
Horses 2 years or younger
71
What parasite is the the cause of parasitic pneumonia in equines?
Dictyocaulus arnfieldi
72
Whats the source of parasitic pneumonia?
Donkeys and mules are asymptomatic carriers and will transmit it to horses
***horses and donkeys do not have to be in the same field they just have to be close***
Foals>Adults
Prevalence
o Donkeys = 68-80%
o Mules = 29%
o Horses = 2-11%
73
Whats the pathogenesis of parasitic pneumonia caused by D. arnfieldi?
* Prepatent period 2-4 months
* Donkey --> Horse transmission
* Horse --> Horse transmission also possible
* Adults living in airways leads to inflammation --> makes horse cough, have bronchospasms and exercise intolerance
74
Lifecycle of D. arnfieldi?
* Ingestion of infective L3 from pasture
* Larvae migrate from intestine through the lymphatic system and blood to the lungs
* Maturation in the lungs
* Adult females lay eggs
* Eggs coughed up, swallowed, and passed in feces
* Eggs hatch almost immediately into L1s
75
What are the two ways that the larvae of D. arnfieldi can spread?
1. Earthworms:
* Ingest larvae and then move across the pasture
* Larvae pass through digestive system unharmed
* Now horse can ingest it
2. Fungus (Pilobolus):
* Develops on piles of manure
* Infective larvae disperse with the fungal spores
* When the fungus bursts it allows the larvae to travel long distances
76
What are the clinical signs of parasitic pneumonia?
None
* Chronic cough
* Bilateral nasal discharge
* Increased respiratory rate and effort
* Auscultation – crackles and wheezes (dorsocaudal lung fields)
* Similar to equine asthma
77
How do you Diagnose parasitic pneumonia?
TTW/BAL=eosinophils
**Peripheral eosinophilia is inconsistent**
ID of D. arnfieldi in the sediment of centrifuged mucus
Baermann fecal exam of patent infection
78
How do you treat and prevent horses with parasitic pneumonia?
Ivermectin or moxdectin
Separate horses from donkeys (unless known to be free of lungworms)
Also deworm the donkeys !!!
79
What is Rhodococcus equi?
Causes foriegn body pneumonia!!
* Gram-positive pleomorphic coccobacillus
* Chinese character formations – L and V clusters of organisms
* Facultative intracellular pathogen
80
Where will you find Rhodococcus equi in the body and what are the two forms of it?
o Persist in and destroy alveolar macrophages
o Virulent (VapA) and avirulent forms
**VapA – virulence factor expressed on the bacterial surface in a temperature-regulated manner
81
Define the Rhodococcus equi infection in horses.
is a suppurative bronchopneumonia with extensive abscess formation that is sometimes accompanied by ulcerative typhylocolitis and mesenteric lymphadenopathy. Occurs in foals 1-6 months of age.
82
What are some characterstics of Rhodococcus equi?
* Soil organism --> Once a farm has it were always worried about it
* Carried in the intestinal tract of foals up to 3 months of age where it can multiply
* Adult herbivores can harbor organism in the intestinal tract
* Transmission via inhalation of dust containing the bacteria (most common) or ingestion (worse in dry climates – i.e. Texas)
* Horses that ingest the organism can develop immunity through exposure via inhalation
* 1-6 month old foals (when maternally derived immunity is waning)
* Insidious disease – may have significant lesions prior to development of clinical signs --> by the time you see clinical signs you have probably been dealing with it for quite some time
83
What are the clinical manifestations of Rhodococcus equi?
Chronic suppurative bronchopneumonia
* Early --> mild fever, slight increase in respiratory rate when exercised or stressed
Anorexia, lethargy, fever
Nasal discharge +/- cough
Tachypnea, dyspnea, nostril flaring and abdominal breathing
* Subacute --> found dead or acute respiratory distress with no history of respiratory problems
84
What is the extrapulmonary manifestation of Rhodococcus equi?
Up to 66% of foals with bronchopneumonia
Intestinal manifestations
o Not often clinical
o Multifocal ulcerative colitis and typhylitis
o Suppurative inflammation of colonic and mesenteric lymph nodes
Polysynovitis
o 1/3 of the pneumonic cases
Other manifestations:
*Panophthalmitis, uveitis
* Guttural pouch empyema
* Pericarditis
* Sinusitis
* Hepatic and renal abscessation
* Anemia
85
How do you diagnose Rhodococcus equi?
Bloodwork: hyperfibrinogenemia, neutrophilic leukocytosis, +/- monocytosis
Radiographs: alveolar pattern, regional consolidation and/or abscessation
Ultrasound: BUT this is only for peripheral lesions **can easily miss deep abscesses**
86
Whats the gold standard DX for Rhodococcus equi (it has not previously been mentioned)? and whats one diagnostic that would not be reliable?
TTW with cytology and bacterial culture is gold standard --> bc horses are becoming resistant to many antibiotics
PCR is also good to do with TTW because it will come back quicker and has high sensitivity but susceptibility is not possible.
So interpret results based on overall case presentation
Whats not reliable is serology in individual patients, its mostly for herd level DX
87
What is the treatment for Rhodococcus equi?
Erythromycin (TID PO) + Rifampin (SID PO or BID PO)
Duration= 4-10 weeks
A static and synergistic combination
Decreases the likelihood of resistance
88
What are the side effects of the current treatment for Rhodococcus equi infections?
o Occasional self-limiting fecal softening
o Idiosyncratic hyperthermia and tachypnea
o Clostridium difficile enterocolitis in mares --> IF mare ingests some of the antibiotic it could die
89
What are some alternative treatments to erythromycin for rhodococcus equi infections?
* erythromycin is not used as much because of the side effects so alternatives...
* Azithromycin – once daily, then every other day
* Clarithromycin – twice daily
* Both also used in combination with Rifampin
90
In addition to antibiotics what are some others treatments for Rhodococcus equi infections?
* Oxygen support
* Supportive care: IV fluids, Nutrition
* HBOT
* Monitor fibrinogen and radiographs/ultrasound --> all these lag behind on clinical end
91
Whats the prognosis of Rhodococcus equi infection?
- 70-90% successful treatment
- Decreased with extrapulmonary manifestations of the disease
- Slightly decreased change of racing as an adult
- Performance of those that did race was not statistically different
92
What are our surveillace strategies for Rhodococcus equi infections?
1. Rectal temps daily
2. Fibrinogen levels every 2 weeks
3. White blood cell count every 2 weeks
4. Ultrasound every 2 weeks
Ideally we want to find it before theyre full of abscesses
93
What are the risk factors for Rhodococcus equi?
Heavily used farms, high animal density
Sandy, dusty soils, manure laden areas
94
How do you control for Rhodococcus equi?
o Pasture rotation
o Plant, irrigate dusty paddocks and pastures
o Surveillance strategies
95
How do you prevent Rhodococcus equi?
Hyperimmune plasma:
* Reduces illness and prevents mortality
* 1-2 liters within 48 hours of birth + 1-2 liters at 4-6 weeks of age
* Maintains high antibody levels for 30 days
* Guidelines may vary depending on challenge size, foals age, and farm location
Prophylactic administration of Azithromycin: controversial and not currently recommended
96
What are other names for equine asthma?
* Inflammatory airway disease (mild to moderate asthma)
* Recurrent airway obstruction (severe asthma)
* Heaves
* Broken wind
* Emphysema
* Chronic obstructive pulmonary disease (COPD)
* Pasture associated pulmonary disease
* Hyperactive airway disease
* Pasture associated pulmonary disease
97
What is the definition of equine asthma?
* Naturally occurring respiratory disease
* Periods of recurrent but reversible airway obstruction
* Neutrophil accumulation
* Mucus production
* Bronchospasm
^^last three things all lead to clinical signs
* Decreased compliance (how easily lung expands)
* Increased resistance
* Increased work of breathing --> works harder to get air out because air gets trapped
* Arterial hypoxemia
98
What horses are most at risk at developing equine asthma?
* Horses that are stalled and fed hay (esp dusty hay)
* ~5% are pasture associated
* Increased incidence with age
* **median age is 12 years**
* Familial tendency
99
If you had a young horse that presented with bronchospasm and mucus accumulation would equine asthma be high on your list of differentials?
Most likely not because typically equine asthma is more likely to be seen in older horses. An inflammatory disease would be more likely than asthma but its never impossible.
100
What is the pathophysiology of equine asthma?
1. Inhalation of dusts and molds leads to increased IL-8
2. IL-8 causes neutrophil accumulation
3. Resulting in small airway obstruction ----->> Causing: Inflammatory changes in the wall of the airway, bronchospasm, mucus accumulation
4. Small airway obstruction results in V/Q mismatch (ventilation/perfusion is low)
5. therefore there is inefficient gas exchange and hypoxemia
6. The horse will then compensate by increasing respiratory rate to try to get rid of CO2 while maintaining the same tidal volume
7. This results in abnormal breathing pattern
## Footnote
* Inhaling the same tidal volume in less time requires that the asthmatic horse develop a higher mean airflow rate in the face of airway obstruction
101
What is some important history to obtain from owners about a horse if you are concerned about Equine Asthma?
* Stalled horse eating hay
* Cough – may be only intermittent with no other clinical signs; may be elicited by tracheal palpation and/or exercise or during dusty times (feeding, stall cleaning, beginning of exercise)
* Exercise intolerance or prolonged recovery from exercise
* Intermittent to frequent serous to mucopurulent nasal discharge
* Occasional bouts of respiratory distress (seasonal?) with flared nostrils
102
What are the clinical signs of Equine Asthma?
Cough
Nasal Discharge
Flared nostrils
Increased respiratory rate
Rapid inspiration and forced prolonged expiration
Weight loss
Increased effort of breathing
Heave line
103
Whats a heave line?
hypertrophy of the external abdominal oblique muscle
104
What will you hear on pulmonary auscultation in horses with Equine Asthma?
* Quiet OR Increased especially in periphery
* Crackles in periphery on inspiration, Caused by the "popping open" of small airways and alveoli collapsed by fluid, exudate, or lack of aeration during expiration
* Wheezes-end expiratory --> most common, Heard when air moves through a narrow opening over fluid
* Tracheal rattle may be present
105
How do you diagnose Equine Asthma?
* History and clinical signs
* Routine Bloodwork will be NORMAL
* Arterial Blood gas
* BAL
* TTW-less reliable
* Radiographs
* Lung function test- need a high speed treadmill
* Atropine or Buscopan test
* Allergy testing
106
What are we looking for on arterial blood gas in a horse with Asthma?
Depends on the magnitude of respiratory compromise but: Chronic respiratory acidosis with hypoxemia, and can show the magnitude of respiratory compromise
107
What are we looking for on BAL in a horse with Asthma?
non-degenerative neutrophilic inflammation
o Negative culture for pathogens (can occasionally have secondary bacterial infection due to decreased mucociliary clearance of pathogens in advanced/untreated cases)
o Does not usually show engulfed or free bacteria
108
What are we looking for on radiographs in a horse with asthma?
Were trying to rule out other lung diseases
Increased bronchovascular and interstitial changes
Lung hyperinflation
109
Whats the atropine or buscopan test done in equine asthma?
anti-cholinergics
These are short lived bronchodilators
Used in dyspneic patients to determine the reversibility of bronchoconstriction
Reduction in dyspnea and respiratory rate should occur within 5 minutes --> they might look like theyre still breathing hard but wheezes usually stop with these tests
However they are associated with the development of ileus (atropine more than buscopan)
110
How is allergy testing done in horses with asthma?
takes serum and they do intradermal injections on neck
Its contraversial, not sure as to whether or not it correlates with lung issues
Used to determine to which allergens a patient is sensitive
*takes 1 year to initally hypersensitize them to the allergens then you will see the effects of the allergens.
111
What is the principal treatment for Equine Asthma?
1. Environmental control *this is a MUST*
2. Reduce inflammation
3. Relieve respiratory distress
All three used at all disease stages
112
How do you control the environment for a horse with asthma?
* First line of treatment for mild cases
* The goal is reduction of exposure to environmental allergens, irritants, and antigens
* House them outdoors 24/7 for improved ventilation
* bedding- paper or pelleted is less dusty, cardboard is great
* Diet- hay is a big problem so you can just soak hay so its less dusty or change to a pellet feed
113
Reduce inflammation in horses with asthma by using what?
* NSAIDs: contraindicated; decrease production of PGE2 which is a good protanoid that inhibits inflammation and prevents bronchospasm
* Corticosteroids: systemic or inhaled
114
What are some systemic corticosteroids you would give an asthma horse?
- Dexamethasone, Prednisolone, Triamcinolone
- Oral or injectable
- Side effects!!
- Use lowest dose possible and wean off ASAP
- Helps to prevent airway remodeling
115
What are some inhaled corticosteroids you would give an asthma horse?
- Beclomethasone, fluticasone
- Metered dose inhalers
- Not for use initially or in an emergency
116
In an emergent situation what would your treatment of choice be for an asthmatic horse if you needed to relieve symptoms ASAP?
Systemic corticosteroids
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Whats a corticosteroid you could add to a nebulizer to treat asthma horses?
Dexamethasone!
EX of nebulizer: Aservo Equihaler, this has absolutely zero systemic absorption but this inhaler is not replacable so you have to get a whole new one everytime you run out. lasts about 10 days
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How do you treat respiratory distress in horses with asthma?
You can relieve respiratory distress by using bronchodilators.
Three classes: Anticholinergics, Beta2-adrenergic agonists, Methylxanthines
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What are the two anticholinergic bronchodilators used for asthma horses?
- Atropine (IV) --> ileus and excitement with repeated doses
- Ipratropium (inhalation)--> used with aeromask, no side effects bc not absorbed
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What are the two Beta2 agonist bronchodilators used for asthma horses?
- Clenbuterol (oral or IV) --> Only one FDA approved bronchodilator for horses, $$$
- Albuterol (inhaled or nebulized, not well absorbed orally) --> inhaled via aeromask, getting to oral does that do help with breathing is hard because theyre almost always too toxic
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What is the methyxanthine bronchodilator used for asthma horses?
- Theophylline (oral) --> erratic absorption and narrow therapeutic index
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What are some other treatments used for asthma horses not previously mentioned?
* Mucolytic drugs?? Acetylcysteine, Saline nebulization
* Antihistamines?? Usually doesnt work
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How do you prevent Equine Asthma?
Clean, well ventilated housing
Proper treatment and manament of respiratory diseases
Prevention as far back as neonatal period
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Whats the prognosis of a horse with asthma?
* Dependent on the stage of the disease
* Reversal of chronic airway remodeling unknown
* Prevention of recurrences of airway inflammation is essential
* Rigorous measures necessary to maintain lung health – $$$
* Cessation of disease progression is good with proper management
| They typically will always have asthma
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What is Pleuritis/pleuropneumonia?
Inflammation of the linining of the thorax and covering of the thoracic organs with the eventual accumulation of excessive fluid in the thorax
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What causes pleuritis?
* Extension of pulmonary disease such as pneumonia or viral/bacterial diseases (most common) --> 2/3 to 3/4 of cases
* Trauma
* Esophageal puncture
* Congestive heart failure
* Neoplasia
* Hematogenous / septicemia – rare
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What are the oropharyngeal bacterial causitive agents of pleuritis?
* Streptococcus spp.
* Pasteurella spp.
* Actinobacillus spp.
* Escherichia coli
* Enterobacter spp.
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What are the anaerobic causitive agents of pleuritis?
* Bacteroides spp.
* Clostridium spp.
* Fusobacterium
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What are the risk factors that lead to increases in pleuritis?
* Long distance transport --> more than 4 hours with head tied
* Strenuous exercise
* Viral respiratory disease
* SX/GA
* Dysphagia
* Systemic Illness
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What is the pathogenesis of pleuritis?
1. Parenchymal inflammation increases
2. Increased permeability of the capillaries in the overlying visceral pleura
3. Out pouring of protein and cells leading to Fluid accumulation within the pleural cavity
4. Bacteria may also invade the pleural fluid
* Acute syndrome will usually produce copious amounts of thoracic fluid, unilateral or bilateral, purulent to serosanguinous
* Chronic syndrome may also produce large amounts of fluid, but the inflammation takes on a fibrinous nature, creating pockets and walled of areas of effusion
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What are the clinical signs of pleuritis?
* Fever
* Lethargy
* Nostril flaring
* Nasal discharge (mild)
* Shallow breathing pattern
* Guarded cough
* Painful silted gait
* Tachycardia
* Ventral edema
| Can be confused with colic or rhabdomyolysis
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What will be heard on ausculation in horses with pleuritis?
pleural friction rubs
ventral dullness
Cardiac sounds radiate due to fluid
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What is heard on percussion in horses with pleuritis?
Painful (pleurodynia)
Dullness
Decreased resonance ventrally
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How do you diagnose pleuritis?
History and clinical signs
Ausculation and percussion
Blood work
Ultrasound
Radiography
Thoracocentesis
Tracheal wash-culture and cytology
Thoracoscopy
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What are we looking for on bloodwork in horses with suspected pleuritis?
- Normal or toxic leukogram
- Neutrophilia or neutropenia if its gram neg
- Hyperfibrinogenemia
| If its chronic CBC might be normal
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Whats the best DX tool and what migh we be looking for on it for a horse with Pleuritis?
Ultrasound!
Pleural fluid, pulmonary abscesses, consolidation, gas echoes
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What are we looking for on radiographs in horses with Pleuritis?
Fluid line
Pneumothorax
Deep abscesses
Best to drain fluid before pictures
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A thoracocentesis as a diagnostic tool for pleuritis is considered..? What can you get from this? Also if theres a foul odor its from what?
- Diagnostic, prognostic, and therapeutic
- Cytology & culture
- Foul odor from anaerobic infection
- *something to remember: horses have fenestrated mediastinums
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What are our treatment goals for horses with pleuritis?
* Remove excess pleural fluid
* Inhibit bacterial growth
* Provide anti-inflammatory and analgesic medications
* Provide supportive care
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How do you drain pleural fluid in horses with pleuritis?
o Indwelling or intermittent
o Indwelling = 24-32 French chest tubes --> use HUGE tubes so they dont get clogged
o Avoid rapid removal of large volumes of fluid
o Heimlich valve
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What are indications for chest tube placement in horses with pleuritis?
- Large volumes of fluid
- Fluid has foul odor
- Horse responds poorly to intermittent drainage
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What are some complications of chest tube placement in pleuritis patients?
- Localized swelling
- Pneumothorax
- Lung laceration
- Hemothorax
- Cardiac arrhythmias
- Puncture of bowel, liver, or heart
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How can we inhibit bacterial growth in pleuritis patients?
o Parenteral Antibiotics: Based on results of culture / sensitivity, Broad spectrum is used
o Oral antibiotics: Switch in 10-14 days depending on response of the animal
o Treat for a total of 2-4 months
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What type of supportive care is given to horses with pleuritis?
o Nasal oxygen
o Anti-inflammatory medications
o Bronchodilators – nebulization of albuterol, clenbuterol
o Fluid therapy
o Nutrition
o Laminitis prevention
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What are common complications we see in patients with pleuritis?
* Antibiotic resistance
* Enteral / parenteral nutrition necessary
* Pleural adhesions
* Bronchopleural fistula leading to acute pneumothorax
- Abscesses requiring drainage via rib resection
- Constrictive pericarditis --> scars and wont expand
* Laminitis
* Jugular phlebitis / thrombosis
* Colitis
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Whats the prognosis of horses with pleuritis?
* Favorable if treated early
* Anaerobic infections have decreased prognosis
* 61% of thoroughbreds treated raced after recovery
* 56% of these horses won at least one race
* Expensive!!!
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What causes pleural effusion?
* Bacterial pneumonia
* Thoracic neoplasia
* Thoracic trauma
* Pericarditis
* Hypoproteinemia
* Congestive heart failure
* Liver disease
* Diaphragmatic herniation
* Equine infectious anemia
* Damage of the thoracic duct
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Whats the pathogenesis of pleural effusions?
Pleural fluid = interstitial fluid of the parietal pleura
1. Elevation of the hydrostatic pressure gradient
2. Decrease in the colloid osmotic pressure
3. Increased permeability of the capillary vessels
4. Decreased removal of fluid due to impaired lymphatic drainage --> main one for neoplasia ex: mediastinal neoplasia
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How do you treat pleural effusion?
* Treat primary cause
* Removal of pleural fluid if horse is having difficulty breathing
* Neoplastic conditions = poor prognosis
