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Equine - 608 > Respiratory > Flashcards

Respiratory Flashcards

1
Q

Explain your diagnostic approach to respiratory disease in horses.

A
  1. History + signalment
  2. Clinical signs + physical exam results
  3. Problem list
  4. Differential diagnosis list
  5. Diagnostic testing
  6. Revised problem list and DDx
  7. Additional diagnostic tests
  8. Diagnosis
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2
Q

What history is important to note when investigating a case of possible respiratory disease?

A

Duration and progression of clinical signs
Any in-contact horses and if they have the same clinical signs
Recent travel
Poor or reduced performance
Exercise intolerance
Changes in management
Vaccination status
Previous or concurrent illness/co-morbidity

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3
Q

List the clinical signs that localise to the upper respiratory tract.

A

Respiratory noise - stertor or stridor
Asymmetrical airflow from nares
Enlarged regional lymph nodes
Guttural pouch enlargement
Facial deformity
Ocular discharge
Unilateral nasal discharge

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4
Q

List the clinical signs that localise to the lower respiratory tract.

A

Adventitious lung sounds
Cough
Bilateral nasal discharge

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5
Q

List the clinical signs that localise to the respiratory tract but not specifically to upper or lower.

A

Increased respiratory effort
Nostril flare - just suggests increased respiratory effort (if bilateral)
Tachypnoea, dyspnoea
Nasal discharge
Epistaxis

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6
Q

List the clinical signs that suggest systemic involvement.

A

Dullness, lethargy
Inappetence
Congested mucous membranes
Tachycardia
Tachypnoea
Pyrexia >38.4 degrees C

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7
Q

What aspects of the physical examination are especially important for a workup of suspected respiratory disease?

A

Demeanour
Head position, facial expression, gait
Respiratory rate
Pattern of breathing
Respiratory effort + noise
Nasal discharge - character, frequency, volume, lateralisation
Symmetry of airflow
Facial deformity - epiphora or ocular discharge
Sinus percussion
Lymphadenopathy, guttural pouch abnormalities
Laryngeal palpation +/- slap test
Tracheal pinch test
Thoracic auscultation - bronchial sounds, vesicular sounds, adventitious sounds

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8
Q

Where would you expect to hear crackles on lung auscultation and what is your interpretation of these noises?

A

Lung fields
Air bubbling through and causing vibration within respiratory secretions

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9
Q

Where would you expect to hear wheezes on lung auscultation and what is your interpretation of these noises?

A

Lung fields
Air flowing through narrowed, vibrating airways, may indicate consolidation

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10
Q

Where would you expect to hear an absence of lung sounds on lung auscultation and what is your interpretation of these noises?

A

Ventrally
Pleural effusion or pulmonary consolidation

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11
Q

Where would you expect to hear pleural friction rub on lung auscultation and what is your interpretation of these noises?

A

Lung fields
Frictional resistance from inflamed pleurae rubbing together

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12
Q

Where would you expect to hear cardiac sounds on lung auscultation and what is your interpretation of these noises?

A

Ventral lung fields
Pleural effusion

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13
Q

What is your interpretation of dullness over the ventral thorax?

A

Pleural effusion
Percussion of lung fields may also elicit a cough or pleurodynia

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14
Q

List the diagnostic tests you can use to investigate equine respiratory disease cases.

A

Physical examination
Rebreathing bag examination
CBC + biochemistry
Blood-gas analysis
Ultrasound
URT endoscopy
Guttural pouch endoscopy
Dynamic endoscopy
Tracheal wash
Tracheal aspirate
Bronchoalveolar lavage (BAL)
Nasopharyngeal swab
Radiography
PCR
C&S
Cryptococcus antigen test
Sinus trephination
Sinoscopy
Thoracocentesis
Lung biopsy

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15
Q

Explain how to do and interpret a rebreathing bag examination.

A

Place a bag over the nares and mouth for 3 minutes - during this time you can listen to areas of suspicion, if there is any coughing during the exam this is an abnormal finding
It should take 30-45 seconds to increase depth of respiration, if its faster than this then suspicion of lower respiratory tract disease

Once the bag comes off a normal horse should recover within 3 breaths

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16
Q

If we are suspicious of an infectious respiratory disease where do we want to swab?

A

Nasopharyngeal swab, tracheal wash, guttural pouch wash
Send off for equine respiratory PCR

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17
Q

Explain the difference between a tracheal wash and tracheal aspirate and when its appropriate to use each.

A

Tracheal wash - done through endoscope, not sterile procedure, appropriate for non-infectious disease process
Tracheal aspirate - direct sampling from the trachea using a cannula and catheter, sterile procedure, appropriate if suspicious about an infectious disease process

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18
Q

Explain how a bronchoalveolar lavage is performed and what testing you submit the samples for.

A

Pass a tube either blind or via endoscope and push up to 300ml saline into the airway (can do 150ml aliquots and make sure you still get surfactant coming back) - then suck the fluid back and submit it for CYTOLOGY (not culture as its not a sterile procedure)

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19
Q

What is the primary cell type found in a NORMAL bronchoalveolar lavage?

A

Lymphocytes and macrophages (both 40-60% each)

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20
Q

What is the primary cell type found in a NORMAL tracheal wash or tracheal aspirate?

A

Macrophages

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21
Q

Which testing should you do if the horse has a history and clinical signs of infectious respiratory disease?

A

Trans-tracheal aspirate (preferrably), but can also do trans-tracheal wash if you can’t do TTA

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22
Q

Which testing should you do if the horse has a history and clinical signs of non-infectious respiratory disease?

A

Bronchoalveolar lavage (BAL)

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23
Q

Which testing should you do if the horse has a history and clinical signs of non-infectious respiratory disease, however the signs have progressed?

A

Trans-tracheal wash + BAL

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24
Q

What probe size and frequency is ideal for thoracic ultrasound?

A

7.5-15MHz linear probe - depth of 5-6cm
If deeper penetration is required then 2.5-5MHz curvilinear or phased array probe will work better

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25
Q

Describe the thoracic ultrasound findings you might find with respiratory disease.

A

Disruption to the pleural surface (bright white line)
Superficial abscessation or consolidation (hepatised lung)
Pleural effusion
B-lines, comet tails

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26
Q

What diagnostic tests should you send thoracocentesis samples for?

A

Cytology and bacterial C&S

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27
Q

When is a lung biopsy indicated and what testing do we send the sample off for?

A

Only indicated if it changes the treatment plan - treat them vs euthanise
Send sample for histopathology + culture

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28
Q

Name the infectious agent of strangles.

A

Streptococcus equi subspecies equi

29
Q

List the clinical signs of strangles infection.

A

Initially - depression, reduced appetite, pyrexia, unilateral or bilateral mucopurulent nasal discharge, pharyngitis, laryngitis, cough

Later - suppurative lymphadenopathy (submandibular - rupture spontaneously, retropharyngeal - drain through the guttural pouches), purulent nasal discharge, dysphagia, asphyxiation

30
Q

Discuss the onset and progression of signs from infection with strangles.

A

Initial clinical signs occur 3-14 days after exposure
Lymph nodes enlarge 2-4 days after the onset of fever
Lymph node drainage occurs 7-14 days after onset of clinical signs
Lesions are typically healing 20-30 days after the onset of disease

31
Q

How do we diagnose strangles?

A

History and clinical signs - often more than 1 horse affected
Culture
PCR
Serological testing - ELISA

32
Q

Describe the treatment for a horse with strangles that has abscessed lymph nodes with no airway obstruction.

A

Local therapy to facilitate drainage - submandibular vs retropharyngeal
Flushing
NSAIDs
No antibiotics as may delay resolution

33
Q

Describe the treatment for a horse with strangles that has early clinical signs (fever and cough) but no lymph node abscessation.

A

Procaine penicillin G 22mg/kg IM BID
NSAIDs

34
Q

Describe the treatment for a horse with strangles that has been exposed to an infected animal but without any clinical signs.

A

Monitor for an increase in rectal temperature
+/- Procaine penicillin G 22mg/kg IM BID

35
Q

Describe the treatment for a horse with strangles that has retropharyngeal lymph node abscessation resulting in airway compromise.

A

Procaine penicillin G 22mg/kg Im BID +/- Rifampicin
NSAIDs
Tracheostomy
US-guided drainage or endoscopic drainage through the guttural pouch

36
Q

How can we kill off the causative agent of strangles in the environment?

A

Rest pasture for 4 weeks
Organism killed by heat, povidone iodine, chlorhexidine, bleach

37
Q

Describe the preventative measures for strangles.

A

Immunity after natural infection
Vaccination

38
Q

Discuss the management of an outbreak of strangles.

A
  1. Separate horses into 3 groups - red for horses with clinical signs, amber for horses exposed to the red group but with no clinical signs, green for horses not exposed to the red group
    Each group should have its own equipment and all handling and feeding should be done with the green group first then amber then red
  2. Screen for carriers - if in green or amber groups do an ELISA blood test, if negative then they are not a carrier, if positive then do guttural pouch sampling PCR + culture to confirm carrier status or false positive result. If they are in the red group then go straight for guttural pouch sampling PCR + culture.
    Any carriers should be treated based on the clinical presentation.
  3. Dealing with horses entering the property - take a blood sample for ELISA on entry, if negative then quarantine for 2-3 weeks and retest to confirm no rising titre, if negative they can enter the herd, if positive then guttural pouch sample for PCR + culture
    If positive ELISA on entry then go straight for guttural pouch sampling and treat if confirmed carrier
39
Q

Explain what a carrier of strangles is, how and when do we test for them?

A

Most horses will shed the bacteria for 4-6 weeks after infection, approx. 25% will shed for months or years after the infection
Can identify carriers 6-8 weeks after the resolution of clinical signs
Swab from guttural pouches and send for culture + PCR
Treat positive animals with penicillin and test again after treatment to check for resolution

40
Q

How do we treat strangles carriers?

A

Repeated guttural pouch lavage
Local benzyl penicillin in the lavage + systemic benzyl penicillin IV

41
Q

Name the sequelae of strangles caused by immune complex binding to neutrophils and mast cells that leads to the release of cytotoxic products. Is it common?

A

Purpura haemorrhagica
Rare - occurs in 1-2% of Strangles cases 2-4 weeks post acute infection

42
Q

Describe the diagnosis and treatment of purpura haemorrhagica.

A

Diagnosis - history of recent infection or vaccination for strangles, clinical signs (warm, painful oedema), ELISA, skin biopsy (perivasculitis, immune complexes), response to treatment

Treatment - corticosteroids, cold hosing, pressure wraps, antibiotics to cover against persistent antigen release

43
Q

Name 4 factors that increase the risk of broncho or pleuropneumonia and explain how that relates to the pathophysiology.

A
  1. Racehorses
  2. Stressful incidents
  3. Viral respiratory disease
  4. Long distance transportation

Most offending organsisms are ubiquitous to horses environment, but cause disease when pulmonary defense mechanisms are impaired or overwhelmed

44
Q

List the clinical signs common to bronchopneumonia and pleuropneumonia.

A

Moist, soft inducible cough or spontaneous cough in pleuropneumonia
Increased respiratory rate
+/- nasal discharge
Ventral oedema and weight loss more chronically

45
Q

Discuss the presentation of pleurodynia and in wha disease it manifests with?

A

Pleuropneumonia

Presents as low head carriage, abducted elbows, stilted gait, resentment of thoracic percussion, tachycardia, camped under posturing

46
Q

Name the most common aerobic bacteria that causes broncho or pleuropneumonia.

A

Streptococcus equi subspecies zooepidemicus

47
Q

Which anaerobic bacteria can cause pleuropneumonia and how does this affect the prognosis?

A

Bacteroides, Clostridium, Peptostreptococcus, Eubacterium
Prognosis is much poorer

48
Q

Discuss the treatment plan for a case of bacterial pleuropneumonia.

A

Antimicrobials - broad spectrum while waiting for C&S results to return (5 day turn around)
Penicillin 22mg/kg BID IM (procaine) QID IV (benzyl)
Gentamicin 6.6mg/lg SID (IV or IM)
Metronidazole 20-25mg/kg BID PO
Course length depends on improvement in condition - use US, resolution of pleural effusion, clinical signs, repeat CBC to look for improvements

Anti-inflammatories - flunixin 1.1mg/kg IV BID (+ anti-endotoxaemic effect), PBZ 2.2mg/kg or opioids like morphine

Pleural drainage via thoracocentesis - place a thoracic drain (US-guided) if a moderate to large volume of fluid is present

Supportive therapy - nutrition, supplement IV fluids spiked with electrolytes + dextrose; may be hypovolaemic so fluids help with that too
Laminitis support - ice boots, possibly use LMW heparin to reduce microthrombi

Monitor for nephrotoxicity using biochem and urinalysis
Nebulisation of bronchodilators or mucolytics may help if there is parenchymal disease present

49
Q

What are possible sequelae of broncho or pleuropneumonia?

A

Pulmonary abscessation
Cranial mediastinal abscessation
Bronchopleural fistulae/pneumothorax
Laminitis
Endotoxaemia

50
Q

Name the common causative agent of fungal pneumonia in Western Australia and the 2 forms it causes.

A

Cryptococcus gatii

Granulomatous form and miliary form

51
Q

Discuss the treatment of fungal pneumonia.

A

Amphotericin B short term (first week)
Fluconazole long term (months)
Monitor using latex agglutination titre or lateral flow - looking for decreasing titres

52
Q

List the clinical signs of respiratory tract disease in foals.

A

Nasal discharge
Tachypnoea, dyspnoea
Abnormal thoracic auscultation
+/- coughing

Systemic - quiet, lethargic, increased periods of recumbency, inappetence/mare’s bag is hard and dry, reduced suckle reflex, petechiae, tachycardia, congested + tacky MM, prolonged CRT, pyrexia

53
Q

Which diagnostic tests are going to be most useful when investigating foal respiratory disease?

A

CBC + biochem
Blood gas analysis
Thoracic ultrasound
URT endoscopy
Tracheal aspirate
Radiography
C&S

54
Q

Discuss the management of pneumonia in foals.

A

Treat the underlying cause

Antimicrobials - based on cytology, C&S, severity of dx, etc

Supportive therapy - oxygen therapy via nasal insufflation, nebulisation, bronchodilators
Fluid support to maintain tissue perfusion
Nutrition - enteral preferrably but can do parenteral
Good nursing care

55
Q

In a foal younger than 4 weeks old what are the most common causes of pneumonia?

A

Secondary to sepsis is most common
Bacteria for primary pneumonia
Aspiration of either milk or meconium are also possibilities

56
Q

In a foal between 1 to 12 months old what are the common causes of pneumonia?

A

Bacteria - Strep equi subsp. zooepidemicus, Rhodococcus equi, Pasteurella, Bordetella bronchiseptica, Actinobacillus, Salmonella, Klebsiella, Pseudomonas, anaerobes
Viral
Mycoplasma
Parascaris equorum
Fungal

57
Q

Describe the characteristics of Rhodococcus equi including how it is transmitted.

A

Gram positive facultative intracellular pathogen of macrophages
Lives in the soil and is found in faeces
Endemic bacteria
Zoonotic
Transmitted to foals via inhalation (aspiration) or ingestion
Most commonly seen in foals from 3 weeks old to 6 months old

58
Q

List the clinical signs of Rhodococcus equi infection in a foal.

A

Bronchopneumonia signs, pyrexia, tachypnoea, dyspnoea, +/ cough +/- nasal discharge
Extrapulmonary disorder (EPD) - diarrhoea, polysynovitis, intra-abdominal abscessation, abdominal lymphadenitis, uveitis, osteomyelitis, IMHA
GI signs - weight loss, colic, diarrhoea
MSK signs - lameness associated with septic synovitis, non-septic polysynovitis
Ataxia due to spinal abscessation or osteomyelitis

59
Q

Discuss how to diagnose Rhodococcus equi infection in foals.

A

CBC + biochem - mature neutrophilia, anaemia of chronic disease, hyperfibrinogenaemia, hyperglobulinaemia, increase in serum amyloid A
Thoracic US - abscessation, comet tails
Tracheal aspirate - cytology, PCR positive to VapA gene, positive culture for R. equi
Thoracic radiography - abscessation, consolidation

60
Q

Explain the appropriate management and treatment of a foal with Rhodococcus equi infection.

A

A majority of foals (88%) with subclinical lesions recover without treatment
Screen using thoracic US and selectively treat those with clinical signs and/or lesion scores >10cm
Perform physical exams on each foal daily including temperature checks and screen with US once a week

Combination antimicrobials for 2-12 weeks
Erythromycin 25mg/kg PO q6-8h OR azithromycin 10mg/kg PO q24h for 7 days then EOD OR clarithromycin 7.5mg/kg PO q12h OR doxycycline 10mg/kg PO q12h
PLUS rifampicin 5mg/kg PO q12h OR 10mg/kg PO q24h (keep in mind that the addition of rifampin reduces bioavailability of macrolides)

Supportive care if severe illness - may need IVFT, active cooling, etc.

61
Q

Describe how to prevent Rhodococcus equi infections in foals.

A

Impossible to eliminate R. equi from the environment and it is not associated with poor hygiene or management, there is also no vaccine
Limit stocking density
Manage pastures to reduce faecal contamination
Segregate clinical cases to reduce aerosolised R. equi and faecal contamination
Screen - $$
Commercial hyperimmune plasma - $$$$

62
Q

Describe the characteristics of equine influenza virus.

A

Orthomyxoviridae, Influenza A
RNA virus classified by surface glycoproteins H and N - subtyping H7N7 (A Equine 1) and H3N8 (A Equine 2)
Short incubation period
Viral shedding starts 24 hours after infection and lasts 4-10 days
Transmission via aerosolized droplets + fomites
No carrier state

63
Q

List the clinical signs and average duration of infection for equine influenza virus.

A

Pyrexia (often severe), peaks at day 2-4
Complete refusal of feed
Dry non-productive + painful cough
Lymphadenopathy
Nasal discharge serous to mucoid after 3-4 days
Stiffness
Poor performance
Secondary bacterial infection indicated if pyrexia lasts more than 5 days and/or purulent nasal discharge present

64
Q

Discuss the diagnosis of equine influenza virus.

A

CBC - non-specific initial lymphopaenia then neutrophilia
Antigen detection
Virus isolation
Immunoassays
PCR
Antibody detection

65
Q

How do we manage and treat horses with equine influenza virus?

A

Contact the Emergency Animal Disease Watch hotline

NSAIDs
Rest - typically 3-4 weeks minimum, 1 week out of work for every day of fever (training break)
+/- antimicrobials if secondary bacterial infection

66
Q

Name the 2 most important subtypes of equine herpes virus and which sorts of disease they cause?

A

EHV-1 - abortion, neurological, perinatal disease, respiratory disease
EHV-4 - respiratory disease

67
Q

Discuss the diagnosis and prevention of equine herpes virus.

A

Diagnosis - virus isolation, nasopharyngeal swab, antibody detection by serology, PCR antigen detection

Prevention by vaccine

68
Q

Differentiate between the clinical signs of equine rhinitis virus A and B.

A

A - fever for 5 days, nasal discharge, moist cough, mild regional lymphadenopathy
B - slight pyrexia, very mild respiratory signs

69
Q

List the clinical signs of equine viral arteritis.

A

Primary vascular lesion affecting multiple tissues including lung + placenta
Pyrexia - up to 41 degrees C
Conjunctivitis, periorbital oedema
Cough + nasal discharge
Body + limb oedema

Equine - 608 (8 decks)

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