Disorders of the Equine Lower Resp Tract 2 Flashcards
what are the differentials for coughing (13)
- severe equine asthma and SPA-SEA
- mild to moderate equine asthma
- URT inflammation/irritation/trauma
- influenza, equine herpes virus etc
- S. equi equi infection (Strangles)
- dysphagia
- bacterial or viral pneumonia
- parasitic pneumonia
- URT/LRT foreign body
- neoplasia
- pulmonary edema
- neoplasia
- smoke inhalation
when should you assume infectious respiratory disease
- pyrexia
- is the horse unwell?
- enlarged lymph nodes
- other animals effected
what is the difference between tracheal and bronchoalveolar lavage
what age of horse does mild to moderate equine asthma affect
young athletic horses but it can be any age
what are the clinical signs of horses with mild to moderate equine asthma (4)
- exercise intolerance/poor performance
- coughing
- increased resp secretions
- no increased expiratory effort (dyspnea) at rest –> but perhaps at exercise
what is the etiology of mild to moderate equine asthma (4)
- environmental dusts/organic particals/gases etc
- bacteria/virus
- genetics, immune status
- exercise induced pulmonary hemorrhage (EPIH)
how is mild to moderate equine asthma (5)
- history and clinical exam
- endoscopy
- cytology particularly of BAL
- pulmonary dysfunction
- pulmonary hypersensitiviy
how is mild to moderate equine asthma diagnosed on endoscopy
+/- tracheal mucus (often excessive)
TW with culture to rule out bacterial infection
what is seen on BAL cytology with mild to moderate equine asthma
neutrophilia
some may have increased inflammation 5-20% of differential count
how is mild to moderate equine asthma treated
similar to SEA
- low dust environment
- corticosteroids
what are the types of corticosteroids used to treat mild to moderate equine asthma
systemic
inhaled
how is the mild to moderate equine asthma response of treatment monitored
subclinical so need to repeat BAL cytology to confirm
how is mild to moderate equine asthma prevented in young horses
- low dust environment (feeding/housing/bedding) –>avoid peak concentrations, mucking out etc.
- good ventilation
what is the difference in signalment with mild/moderate vs severe equine asthma
MEA usually young adults
SEA > 7 years
what are the difference in clinical signs in mild/moderate vs severe equine asthma
MEA: no dyspnea at rest, may have tachypnea
what are the differences in BAL cytology in mild/moderate vs severe equine asthma
what is the difference in prognosis of mild/moderate vs severe equine asthma
MEA: short duration, can resolve spontaneously or with treatment, low risk of recurrence
SEA: long duration, recurrent
what is exercise induced pulmonary hemorrhage
common pulmonary disorder of the hrose
associated with strenous exercise
what is the pathogenesis of EIPH
unknown
stress failure of pulmonary capillaries
may be associated with mild/moderate equine asthma
low alveolar pressure?
upper airway obstruction?
mechanical forces associated with poor performance?
does EIPH cause poor performance
moderate to severe EIPH associated with reduced performance
BUT many horses have EPIH without impaired performance
what are the presenting signs of EIPH (5)
- none
- +/- post exercise/race epistaxis
- +/- poor performance
- +/- repeated swallowing post exercise/race
- +/- prlonged recovery post exercise/race
what are the clinical signs of EIPH
- none
- +/- epistaxis
- +/- abnormal lung sounds (rarely)
how is EIPH diagnosed
- endoscopy (30-60 min post exercise)
- BAL cytology: free red blood cells, hemosiderophages, +/- neutrophils
how is EIPH treated
aim to reduce hemorrhage, minimize sequelae (inflammation/fibrosis)
how can frequency of EIPH episodes
altered training
prophylaxis –> frusemide
what is interstitial lung disease
acute or chronic inflammatory process of primary alveolar walls and adjoining bronchiolar interstitium
what does acute phase interstitial lung disease
present in acute respiratory distress
how does chronic phase interstitial lung disease present
presents clinically like SEA
what are the causes of interstitial lung disease (3)
multifactorial
- toxic agents: mineral oil, silicosis
- infectious agents: bacteria, virus, parasite
- idiopathic
how is interstitial lung disease diagnosed
process of elimination and radiography
how is interstitial lung disease treated
treat infectious agent (if present) and anti-inflammatory therapy
what is equine multinodular pulmonary fibrosis (EMPF)
a progressive fibrosing lung disease associated with presence EHV-5
when is equine multinodular pulmonary fibrosis seen
typically in older horses
often intially suspected to be SEA or infectious bronchopneumonia
what are the signs of equine multinodular pulmonary fibrosis (EMPF) (4)
- tachypnea
- tachycardia
- weight loss
- pyrexia
what can be heard on auscultation with equine multinodular pulmonary fibrosis (EMPF)
wheezes and crackles
how is multinodular pulmonary fibrosis differentiated from SEA
prove it is NOT reversible –> administer short acting bronchodilator? buscopan
how is multinodular pulmonary fibrosis differentiated from infectious pneumonia
BAL cytology –> non septic neutrophilia
what is seen on BAL samples with multinodular pulmonary fibrosis
presence of EHV-5
what is seen on radiography with multinodular pulmonary fibrosis
diffuse, nodular interstitial pattern
what is seen on ultrasonography with multinodular pulmonary fibrosis
diffuse pleaural thickening
may identify nodules superficial in lung
biopsy
how is multinodular pulmonary fibrosis treated
fair to poor prognosis
dexamethasone, doxycyline, acyclovir
what causes lungworm
Dictylocaulus arnfieldi
what is a question you should ask when examining a horse to distinguish SEA from lungworm
has there been any contact with donkeys/mules
what is seen with horses on lungworm
- BAL cytology
- larvae in tracheal wash
- few eggs in feces as usually not patent infection in horses
how is lungowrm treated
oral ivermectin/moxidectin
what ascarids can migrate into the lung
Parascaris equorum
what does Parascaris equorum cause
larval migration in foals/yearlings –> lung inflammation and clinical signs
but can cause intestinal obstruction/intussusception
ill thrit and diarrhea
how long does it take for Parascaris equorum to cause an infection
3 months to become patent infeciton
relatively minor
how is Parascaris equorum diagnosed
fegal worm egg count when patent infection
how is Parascaris equorum prevented
deworming
what is bacterial pneumonia
bacterial infection of the lung parenchyma
bronchopneumonia with or without involvement of the pleural space
what is the etiology of bacterial pneumonia
bacteria (normal inhabitants) from nasal or oropharynx –> reach lower airways and overwhelm the defences
what gram positive species can cause a bacterial pneumonia
- Streptococcus equi ss zooepidemicus*
- Staphylococcus aures*
- pneumoniae*
what gram negative species can cause bacterial pneumonia (5)
- Actinobacillus*
- Pasteurella species*
- E. Coli, Klebsiella*
- pneumoniae*
- Bordetella bronchiseptica*
what obligate anaerobes can cause bacterial pneumonia (3)
- Bacteroides fragilis*
- Fusobacterium*
- Clostridial species*
can fungal species cause bacterial pneumonia
rarely
usually immune suppression or prolonged use of antimicrobials
what is the pathogenesis of bacterial pneumonia and what does the development require
transient contamination of LRT with URT bacteria common in healthy horses
potentially pathogenic and non-pathogenic bacteria (and fungi) can be isolated from tracheal washes from healthy horses
so development of pneumonia requires
- overwhelming bacterial challenge
- impairement of pulmonary defences
what events can cause an overwhelming challenge of LRT
- aspiration
- head elevation (transport)
- laryngeal/pharyngeal dysfunction
what aspiration events can cause bacterial pneumonia
- feed
- near drowning
- esophageal obstruction (choke)
what events can cause laryngeal/pharyngeal dysfunction which lead to bacterial pneumonia (4)
- surgery
- botulism
- myopathies
- cranial nerve dysfunction causing dysphagia (GP mycosis affected CN 9 and CN 10)
what events can cause impaired LRT defences (5)
- exercise
- prior viral infection
- transport
- GA and surgery
- environmental conditions
what exercise events can lead to impaired LRT defences causing a bacterial pneumonia
- aspiration of dirt (racetrack)
- impaired local and systemic immunity (stress of intense exercise)
how can prior viral infection cause impaired LRT defences
impaired mucociliary clearance
how does transport lead to impaired LRT defences (2)
- impaired mucociliary clearance
- impaired leukocyte function
how can environmental conditions lead to impaired LRT defences
- noxious gases, particulate matter, endotoxin
- ventilation, co-mingling, husbandry
what are the presenting signs of bacterial pneumonia (7)
- can be subtle initially
- pyrexia
- inappetence, signs of depresion (first signs)
- exercise intolerance
- cough: usually soft, moist
- nasal discharge: purulent, serosanguinous, malodorous
- tachypnea, hypopnea, resp distress
what are the systemic signs of bacterial pneumonia
Evidence of systemic inflammatory response syndrome (SIRS)
Tachycardia, mucous membranes, etc
Laminitis?
what are the signs of bacterial pneumonia with auscultation (3)
- Exudate in trachea
- Increased inspiratory noise with wheezes and crackles ventrally
- Reduced breath sounds ventrally? Pleural effusion?
what are most cases of bacterial pleuropneumonia extensions of
bacterial pneumonia
how does bacterial pneumonia cause bacterial pleuropneumonia and what can this lead to if left untreated
if inflammation extends to pleural space causing sterile fluid accumulation
If not treated bacteria migrate into the fluid and multiply
Septic exudate and fibrin production
what other things can cause bacterial pleuropneumonia
pulmonary abscesses
trauma
esophageal rupture
what are the signs of severe acute bacterial pleuropneumonia (6)
- tachycardia, toxic mucus membranes —> SIRS
- Pleural friction rubs on auscultation
- Pleural fluid (diminishes as fluid accumulates)
- Shallow breathing depth with increased rate
- May present with apparent colic signs (false colic)
- Pain on palpation of thorax, “grunt”, reluctant to move
what are the chronic signs of bacterial pleuropneumonia
intermittent fever/weight loss
how is bacterial pleuropneumonia diagnosed (7)
- history + clinical signs
- hematology + biochemistry
- endoscopy
- tracheal wash
- ultrasonography
- radiography
- thoracocentesis
what is seen on hematology and biochem with bacterial pneumonia/pleuropneumonia
- Leukocytosis with absolute neutrophilia: severe may have a neutropenia (gram negative bacteria?)
- Anemia of chronic inflammation
- Positive acute phase proteins: fibrinogen and serum amyloid A elevated (SAA goes up within hours of onset of infection)
- Negative acute phase protein: decreased albumin
- Increased globulins
what is seen on endoscopy with bacterial pneumonia/pleuropneumonia
Laryngeal/pharyngeal abnormality?
Mucopus in trachea
what is seen on tracheal wash cytology with bacterial pneumonia/pleuropneumonia
culture for aerobic and anaerobic
cytology:
- Increased neutrophils >40% but up to 100% possible
- Degenerate neutrophils and bacteria (intracellular)
what is seen on ultrasonography with bacterial pneumonia/pleuropneumonia
- Comet tails —> pleural thickening
- Lung consolidation
- Abscesses
- Pleural fluid, fibr
where are most ultrasonographic findings found with bacterial pneumonia/pleuropneumonia
ventral
why are most ultrasonographic findings found ventrally in bacterial pneumonia/pleuropneumonia
because aspiration follows gravity –> ventral lung fields most affected
how is the lung field scanned in bacterial pneumonia/pleuropneumonia
caudal to cranial
dorsal to ventral
identify end of lung field within each IC space
which side of the thorax is more affected with bacterial pneumonia/pleuropneumonia
right hemithorax –> more direct route
how is bacterial pneumonia/pleuropneumonia treated
broad spectrum antimicrobial therapy in interim while waiting for culture and sensitivity
what antimicrobials are used in bacterial pneumonia/pleuropneumonia
Penicillin + gentamicin +/- metronidazole
(Ceftiofur?/cefquinome? +/- gentamicin +/- metronidazole)
how long are antimicrobials indicated usualyl for bacterial pneumonia/pleuropneumonia
6-8 weeks or longer usually
then eventually switch to oral depending on sensitivity: TMPS/enrofloxacin/doxycycline
what else can be used to treat bacterial pneumonia/pleuropneumonia (2)
- nebulize antibiotics (gentamicin, cefquinome, ceftiofur)
- Saline: breaks up the pus and gets rid of it
what supportive therapy can be used to treat bacterial pneumonia/pleuropneumonia (8)
- Bronchodilation: clenbuterol (also helps with ciliary clearance)
- NSAIDs: flunixin meglumine (endotoxins floating around)
- Remove plural fluid: chest drain (lavage?) –> especially if in respiratory distress
- Fibrinolytics (tissue plasminogen activators) within pleural space
- Hydration: IV fluids, correction of fluid and electrolyte derangements
- Good ventilation
- Low dust environment
- No stress
how can the response to treatment be monitored in bacterial pneumonia/pleuropneumonia (4)
Expect improvement within 48-72 hours
- Clinical exam: important in determining response to treatment –> are respiratory parameters returning to normal? Is body temperature within normal limits? Chest fluid level decreasing? (ultrasonography)
- Hematology: acute phase proteins –> fibrinogen and serum amyloid A (may be a guide when to stop antimicrobial therapy)
- Ultrasonography
- Radiography
what complications can occur in bacterial pneumonia/pleuropneumonia (8)
- abscess formation
- pleural adhesion/abscess
- Cranial mediastinal mass/abscess
- Laminitis
- Broncho-pleural fistula
- Thrombophlebitis
- Pneumothorax
- Pulmonary necrosis
what agents can cause bacterial pneumonia/pleuropneumonia in foals
Streptococcus zooepidemicus most common
Also Rhodococcus equi (also known as Rhodococcus hoagii/Prescotella equi)
at what age can foals be affected by bacterial pneumonia/pleuropneumonia in foals
1-6 months
infected by inhalation
what type of bacteria is Rhodococcus equi
gram positive faculatative intracellular organism
where is Rhodococcus equi found
in the environment
wildlife reservoir
at what age are foals affected by Rhodococcus equi
3 weeks to 6 months
how are foals infected with Rhodococcus equi
inhaled
what can Rhodococcus equi cause in foals
can be insidious and can progress to acute resp distress and death
Suppurative bronchopneumonia with abscesses
how is Rhodococcus equi diagnosed (4)
- Auscultation
- Hematology and biochemistry
- Ultrasonography/radiography
- TW wash culture and cytology
how is Rhodococcus equi treated in foals (2)
- Antimicrobial needs to have high volume of distribution –> good penetration as intracellular & long duration 4-9 weeks
- Supportive therapy: intranasal oxygen and IV fluids
what antimicrobials are effective in treating Rhodococcus equi
Rifampin plus a macrolide (work really well together)
Rifampin and azithromycin
Rifampin and clarithromycin
Rifampin and erythromycin (used less often now —> diarrhea in mare and foal because mare eats feces of foal and can cause colitis)
what are other causes of pleural effusions (6)
- Thoracic neoplasia: second most common
- Congestive heart failure: especially right sided
- Thoracic trauma: pleuritis, hemothorax
- Hypoproteinemia
- Coagulopathy (rare)
- Chylothorax (rare)
what is the pathogenesis of pleural effusion (4)
- Increased permeability in capillary vessels:
- Increased in hydrostatic pressure:
- Decrease in osmotic pressure:
- Decrease in fluid removal:
what is the pathogenesis of increased permeability of capillary vessesl that can lead to pleural effusion
infection
inflammation
neoplasia
what is the pathogenesis of increased hydrostatic pressure that can lead to pleural effusion
- congestive heart failure
- portal hypertension
what is the pathogenesis of decrease in oncotic pressure that can lead to pleural effusion
- hypoproteinemia
what is the pathogenesis of decrease in fluid removal that can lead to pleural effusion
- impaired lymphatic drainage or obstruction –> neoplasia
- pleural or parenchymal infiltration –> neoplasia
what is the most common neoplasia that can cause pleural effusion
lymphomas
how are lymphoma neoplasias classifed (4)
multicentric, alimentary, cutaneous, mediastinal
when is lymphoma neoplasia common in horses
More common in young adult horses (but rare overall)
5-10 years
are lymphoma neoplasias in horses leukemic
not usually
what is most common neoplasia in thorax
Most common neoplasia of thorax: mediastinal
Primary thoracic neoplasia
Often cranial mediastinal mass
Associated with pleural effusion
what are other neoplasias that can cause pleural effusions (3)
- Mesothelioma: primary thoracic tumour
- Pulmonary granular cell tumours: primary lung tumour –> may be diagnosed as SEA. Bright red nodules may be visible in airways
- Metastatic neoplasia: adenocarcinoma, melanoma, hemangiosarcoma, squamous cell carcinoma
