Eqine respiratory conditions Flashcards
Which lymph nodes can we feel around the head for lymphadenopathy
Submandibulars
cannot feel retropharyngeals externally
What type of virus is equine influenza
ssRNA orthomyxovirus type A
CLinical signs of equine influenze
Pyrexia, inappetance, lethargy, nasal discharge
Dry persistent cough very noticeable often
Diagnosis of equine influenza
Do nasopharyngeal swabs while animal is sick
How does vaccination against equine influenze help
Reduces shedding and severity but does not prevent infection
Vaccine schedule for influenza
First vaccine
Then second one within 21-60 days
Third one 120-180 days
Then booster 6-12 monthly
How to deal with equine influenza case
Isolation for 14 days
Long rest and recovery
NSAIDs
Only do antibiotics if there is a secondary infection
What is the cause of strangles and what type of bacteria is it
Streptococcus equi v equi
= gram +ve cocci
Pathogenesis of strangles
Bacteria enter oro-nasal cavity and enter cryp cells of tonsil –> spread to regional lymph nodes and cause lymphadenopathy
Then a few days later get lymphoid hyperplasia and abscessation
From 7 days + can get rupture of the LN which causes infectious pus to come out of nose via floor of guttural pouch
How can we try and isolate horses before LN rupture in strangles
They have pyrexia before the rupture so isolate them then
Should do 2X daily temperature checks for any in contacts of a confirmed case
Can we get endemicity of strangles
Yes because a small % remain persistently infected
Why is strep equi v equi so important
Can be fatal via asphyxiation or by high cost of treatment
Can spread easily in residential premises
What aerosolises more out of influenza and strangles
Influenza
(strnalges does not aerosolise much)
Clinical signs of strangles
Pyrexia, lethargy, mucopurulent nasal discharge, submandiular/retropharyngeal lymphadenopathy, inappetance/dysphagia
+ less commonly, higher resp rate and effort, stridor, can mimic choke with water/food down nose
Which LNs are located near the floor of the guttural pouch
Retropharyngeals
Why can horses with strangles be dysphagic
1) Physical obstruction due to enlarged LNs
2) Some neuropraxia because enlargeds LNs are interfering with nerves on floor of guttural pouch
Are horses with strep equi v equi chondroids a large risk to population
Not really bceause chondroids usually PCR negative
If they have empyema though they are
What should we consider if we see empyema but negative strangles test
Probably still strangles
What is an appropriate screening test for strangles i.e pre-movement
SCoping guttural pouch and submitted aspirates
ELISAs are NOT useful if there is no clinical suspicion
How does strangles survive in the environment
Not well; especially not in summer
So leaving horses outside with it is a good idea
What can mild strangles look like
Unexplained pyrexia, mild cloudy nasal discharge
In any unexplained pyrexia should check the guttural pouches
What is bastard strangles
Where there is haematogenous or lymphoid spread of strep equi v equi
Leads to purulent material and abscessation wherever the bacteria go
e.g meningitis, skin swelling, mesenteric abscessation
Which animals do we typically see bastard strangles in
Very ill animals that haven’t been given antibioitics
What is purpura haemorrhagica
Severe vasculitis triggered by illness such as strangles
Requires high steroid doses
What does the strangles ELISA detect (and when might it be low or high)
SEM
May not be expressed in persistently infected genomes
Very high titre with purpura haemorrhagica
What are some potential complications of strangles
- Bastard strangles
- Purpura haemorrhagica
- Myopathies
Treating strangles
NSAIDs +/- paracetamol
Give penicillin if horse is persistently pyrexic, dull and miserable, if there is dysphagia or stridor
Flush out guttural pouch via scope or foley catheter (may instill penicillin here)
WHat must we advise owners when giving antibiotics for strangles
Can get poorer seroconversion and may get flare up of abscess after therapy
But if they need it must give
What types of viruses are EHV1,4
alpha herpesviruses
Characteristics of equine herpes virus infection
~80% infected as youngsters
Pyrexia, nasal discharge, cough, lethargy
Abortion may be first clue
Get latency in trigeminal ganglion; rarely get recrudensce
Do we need to isolate latently infected herpes cases
No
What is gold standard for diagnosing equine herpes virus
Virus isolation (but it is slow)
Vaccination schedure for EHV1/4
1st one from 5 months, then another 4-6 weeks later, boost at 6 months
Then give at 5, 7 and 9 months gestation to mares
NB: this vaccine reduces shedding and severity but not prevent abortion or neuro signs; it is licensed for respiratory disease
How does EHV1,4 enter body and proliferate
Enters respiratory epithelial cells, goes to monocytes/lymphocytes then to blood vessels/LNs
Get a cell associated viraemia and replicatino in vessel endothelium
How much rest to give pyrexic horses
1 week for every day of pyrexia
What type of virus is equine viral arteritis
RNA alpha-arterivirus
What does equine viral arteritis cause
Pyrexia, inappetence, conjunctivitis, vasculitis so oedema, abortion
= can be maintained in carrier stallions so should not be kept for breeding
What is the use of a rebreathing exam
Increases the inspired CO2 of horses, making them breathe more heavily and improving sensitivity of auscultation
Becomes easier to hear harsh sounds, crackles from fluid
Or areas of no nosie
What can bloods be useful for in a respiraotry work up
Systemic inflammation is indicative of pneumonia
vs in asthma, the bloods will look normal
What tests is BAL best for
Cytology
What method can be used for resp secretion culture
Tracheal wash if a triple lumen catheter used
Or transtracheal wash is best
What areas do BALs vs TW samples and what does this make them good at identifying
BALs sample just a single region of lung; so good at identifying diffuse disease
TWs sample everything
How to do a BAL
Place long tube up ventral meatus
Use opioid to suppress cough (+ may ahve LA)
Instill ~300ml saline and aspirate back (discarding first syringe)
Place in EDTA tube
What is an indication of a good BAL sample
It is foamy due to surfactant from alveoli
How do we do a tracheal wash
requies endoscopy
Use catheter to instill 20-30ml sterile saline and reaspirate
For culture use plain tube
For cytology use EDTA tube
What bacteria are likely to be contaminants if seen on tracheal wash
pseudomona, S aureus, Bacillus
What is the difference between recurrent airway obstruction and inflammatory aidway disease
RAO = severe asthma i.e increased resp effort at rest, lifelong condition, see coughing too - tend to be >7y/o
IAD = mild/moderate asthma; no signs at rest but occasional cough or exercise intolerance; tends to resolve; generally young
What do asthma BAL results look like
High percentage of neutrophils
- Normal is 5%
- In IAD see >10
- In RAO see >25
Tend to see elevated mast cells in IAD (mild-moderate asthma) as feature of airway hyperresponsiveness
Management of asthma
Low dust; dust extracted bedding, soaked hay, maximum turn out time, improve ventilation, no straw at all
Medication: steroids, bronchodilators
What is exercise induced pulmonary haemorrhage
Where horses undergoing very strenuous exercise get rupture of pulmonary capilaries (thin walled and get low airway pressures and very high vascular pressures in exercise)
If severe can affect performance
What is a fading horse often a symptom of and how do we diagnose
Exercise induced pulmonary haemorrhage
Need to scope in 30-120 mins after exercise and score 0-4 based on blood in airway
IF we see haemosiderophages on BAL what does this suggest
There has been historic exercise induced pulmonary haemorrhage snce this is digested blood
But note this does overestimate prevalence
What should we do if horse has suffered exercise induced pulmonary haemorrhage
Rest and steroids
Want to avoid new bleeds
Can give furosemide before training to prevent bleeding occuring
What area does the following affect: interstitial pneumonia, bronchopneumonia, pleuropneumonia
Interstitial = parenchyma
Bronchophneumonia = parenchyma and bronchi
Pleuropneumonia = parenchyma + bronchi + pleural space
What are risk factors for bacterial pneumonia
Long distance travel because means head not let down for long periods
Cross tying (prevents head going down)
Resp tract disease
Apiration e.g from oesophageal pbstructions, dysphagia
Which cause of bacterial pneumonia has the worst prognosis
Those due to aspiration as have a much larger range of aspirated bacteria vs normal commesnals strep zooepidemicus
If anaerobes involved = worse prognosis
What is the most common bacteria to isolate on TW from bacterial pneumonia
Strep zooepidemicus
Clinical signs of bacterial pneumonia
Tachypnoea, weight loss, pyrexia, cough, nasal discharge
If they have fetid breaths suggests anaerobes involved (worse prognosis)
What would we see on bloods with bacterial pneumonia
leucocytosis +/- left shift, increased SAA, anaemia
What is a good antibiotic selection for bacterial pneumonia
Penicillin + gentamycin + metronidazole
What are some possible complications of bacterial pneumonia
Abscessation
Broncho-pleural fistulae
Pericarditis
Thrombophlebitis
Laminitis
What two types of fungal pneumonia are there
Primary pathogens e.g histoplasma, coccidiodes, cryptococcus
Or those secondary to immunocompromise e.g aspergillus, candida
What might a neurophilic/eosinophilic tracheal wash point towards
Parasitic pneumonia
Signs of interstitial pneumonia
- Exercise intolerance
- Increased effort at rest
- Pulmonary hypertension/cor pulmonale
What can cause interstitial pneumonia
OFten not clear
- Viral e.g EHV, influenza, EVA
Smoke inhalation
What can cause pneumothorax
- Bronchopleural fistulae secondary to pneumonia
- Penetrating thoracic injuries
- Oesophageal peforations
Can be well tolerated if unilateral
What is equine multinodular pulmonary fibrosis
= interstitial fibrosis associated with EHV-5 by unclear pathogenesis
See large discrete or multiple coalescing opacities on radiography
Diagnosis of exclusion
Poor prognosis
Is presumed asthma is not responding to treatment what other condition should we think about
Equine multinodular pulmonary fibrosis
At what temperature should we isolate a horse
38.5
Ideally measure temperature twice per day to get baseline normal temperature and account for diurnal variation
What is the difference between quarantine and isolation
Quarantine = isolation of animals potentially incubating infections; minimum 2-3 weeks
Isolation = separation of animal with known disease to prevent transmission
What does effective quarnatine mean
Physical separation of >10-20m from resident animals or more if influenza
Separate staff and equipment
What are the three types of disease caused by herpes viruses
Respiratory
Abortion
Neurological
How does complement fixation test work
Where antibodies bind to complement, preventing complement from causing RBC haemolysis so we see a pellet or RBCs rather than haemolysis
If we see a horse with heart rate over 60 what does this suggest
Not just related to being in pain; should consider shock
What is our primary concern with a pony which has travelled for a long time and is now pyrexic, high heart rate, high resp rate and effort
Pleuropneumonia
- Because head not down for long periods of time
What is our approach to a case with suspected pleuropneumonia
Don’t need to isolate the horse
Pain relief; paracetamol + fluids
- Ideally check kidneys before NSAIDs
Ultrasound
Pengentmet
What do we need to be aware of when giving an alpha-2 agonist to a horse with a temperature
They look very poor with panting and sweating for ~15 mins after giving sedation; just be aware of this
Treating pleuropneumonia
- Antibiotics; penicilling, gentamcin, metronidazole
- Drain fluid if needed
- Use tissue plasminogen activator to break down fibrinour nets in lungs in some cases
What are haemosiderophages and what do they tell us
Macophages with digested blood in them
Tells us that there is some chronicity to the exercise induced pulmonary haemorrhage; i.e these aren’t from this incident as take time to appear
When should we ideally scope a horse after it has pulled up from a race to tell if EIPH is the cause of this
With 30 mins to 2 hours
- Then grade it on scale; if high at same time as fading episode means likely to be the cause
What condition can lead ot high pulmonary pressures in exercise and epistaxis/pulling up
Atrial fibrillation
Treatment for EIPH
Must have rest; no fast work
Steroids; start with oral prednisolone then move to inhalers as it works more
What type of cells do we see on a tracheal wash from horse with EIPH
Very high neutrophils count
Haemosiderophages
What is a BAL contraindicated
if the horse is struggling the breathe already
If a tracheal wash shows plant material and bacteria what does this suggest
Aspiration pneumonia secondary to choke
What is a heave line
hypertrophy of external abdominal oblique due to increased resp effort
What does severe equine asthma mean
Showing obvious signs at rest; coughing, tachypnoea
Treatment for acute asthma (rescue and maintenance)
Rescue therapy = IV atropine/buscapon, IV dexamethasome
Maintenance; oral preds, oral clenbutor, then inhaled steroids/bronchodilators
Treatment of asthma after acute episode controlled
Management is mainstay
+ steroids; oral prednisolone or IM dex for some owners
Beta-2 agonists?
What are the advantages of the flexineb
Better tolerance from the horse vs baby spacer
Medication cheap to refill once purchase made
Better amount of drug breathed in
Out of tracheal wash and BAL which is better for cytology vs bacteriology
TW = better for bacteriology because no exposure to commensals on way down
BAL = better for cytology
WHat is a normal amount of neutrophils on BAL vs TW
TW: <20%
BAL: <5-10% neutrophils
Which cell type predominates in equine asthma
Neutrophils (NB this is different to humans)
Why are anti-histamines not routinely used in equine arthma
Poor bioavailability
Treatment of fungal pneumonia
Azoles
AMphotericin B (NB: can get phlebitis, anorexia, dysrhythmias, anaemia)
How long to give antibiotics for bacterial pneumonia
4-6 weeks
+ want stall rest and gradual return to exercise
What causes guttural pouch mycosis and what is the treatment
Aspergillus
Topical azoles e.g enilconazole
Could do systemic intraconazole
Treatment of strangles
Symptomatic mostly; NSAIDs, soft foot, hot packing abscesses
Can use antibiotics in some cases
When might we use antibiotics in a strangles case and which do we pick
High fever/malaise
Severe lymphadenopathy causing respiratory distress
Metastatic abscessation
Purpura haemorrhagica requiring glucocorticoids
Choose penicillin
NB: impairs immunity to stranlges developing
Can we use prophylactic antibiotics in a stranlges outbreak
NO
What to do with carrier status strangles animals
Treat with antiibotics
Chondroids require endoscopic removal?
Treatment of influenza
Sympatomatic; rest, hydration, NSAIDs, paracetamol
+ if showing signs of resp distress more than 10 days later can give anitbioics due to high risk of secondary infection
What is key when returning to work after influenza
Do not do too early; can end up with coughing and inflammation for weeks
What antiviral drug would we use in influenza outbreaks or to deal with neurological disease in herpes virus
Valacyclovir
