Respiratory Flashcards
what is the difference in how you feel when you have infectious vs non-infectious disease? (strangles vs asthma…)
infectious - under the weather, lethargic, inappetent…
non-infectious - just difficulty breathing
what are the three classic clinical signs of infectious disease?
group is affected
pyrexia
dullness
what changes on haematology would indicate an infectious disease?
increased white cells
increased acute phase proteins
what are the most commonly used acute phase proteins in horse used to identify infectious disease?
serum amyloid A (rapid increase)
fibrinogen
what is the main issue with using antibodies to detect infectious disease?
there is a lag - have to wait for them to increase in response to the pathogen
what are the subtypes of equine influenza based on?
glycoprotein surface antigens
haemagglutinin (H)
neuraminidase (N)
why are vaccines not great at preventing equine influenza outbreaks?
strong antigenic drift (especially H3N8)
how do the ciliated epithelial cells appear 6 days after equine influenza infection?
completely stripped of cilia
what is the incubation period of equine influenza?
5 days
what are the clinical signs of equine influenza?
fever, cough, oedema/hyperaemia (URT), nasal discharge, lethargy
how long is recovery of equine influenza usually complete by?
3 weeks (unless secondary infection)
what sort of cough is described with equine influenza?
dry/hacking that turn moist
how does the nasal discharge of horses with equine influenza appear?
serous that turn mucopurulent
what is initially found on haematology of equine influenza cases?
lymphopaenia
neutropenia
what occurs on haematology in equine influenza after the initial lymphopaenia and neutropenia?
monocytosis
neutrophilia
hyperfibrinogenaemia
how can serology be used to diagnose equine influenza?
looking for a rising antibody titre (x4) over 2-4 weeks
when is the best time after infection to swab for equine influenza?
2-5 days post infection (when clinical signs are showing) - most shedding
what are the treatment options for equine influenza?
supportive - hydration, NSAIDs…
(antibiotics is secondary infection)
how long do horses with equine influenza require off work?
1 week for every day of pyrexia
why are mortalities associated with equine influenza more common in foals?
more susceptible to developing myocarditis, secondary pneumonia and acute respiratory distress syndrome
how does the equine influenza vaccine help?
reduces the severity of clinical signs and duration of virus shedding
how long can equine influenza survive in the environment?
36 hours (killed easily by cleaning/disinfectant)
what do most foals do when infected with EHV 1/4?
seroconvert to become latently infected, this is then reactivated under stress
what are the forms of EHV ?
respiratory
abortion
neurological
where is EHV 1/4 found latently?
trigeminal ganglia
lymph nodes
how severe is the respiratory disease caused by EHV1?
mild
what happens on haematology in the acute phase of EHV1 respiratory disease?
decreased neutrophils and lymphocytes
after the initial decrease in neutrophils/lymphocytes in EHV1 cases, what happens to the haematology?
increased lymphocytes
what is done to treat EHV1?
symptomatic/supportive - rest, NSAIDs…
antibiotics for secondary infection
what age horse is Rhodococcus equi seen in?
3 weeks to 6 months old
what is Rhodococcus equi also known as?
rattles
what type of pneumonia is caused by rattle?
pyogranulomatous
what disease is rattles similar to in people?
Tb
how is rattles treated?
prolonged antimicrobials - macrolides and rifampin
why is Rhodococcus equi so effective and difficult to treat?
lives intracellularly in macrophages (hard to reach with antimicrobials)
what is strangles caused by?
Streptococcus equi var equi
is Streptococcus equi var equi an obpportunistic or obligate pathogen
obligate
where do carrier animals harbour Streptococcus equi var equi?
guttural pouch
what is the incubation period of strangles?
3-14 days
how do animals present in the incubation period of strangles?
asymptomatic
normally aren’t infectious
when do clinical signs appear in relation to shedding of the bacteria of strangles?
depression and fever appear 2-3 days before shedding
what are the clinical signs of strangles?
depression, fever
mucoid nasal discharge
slight cough
anorexia and difficulty swallowing
mild pharyngeal swelling
when monitoring horses in a strangles outbreak, what is done?
monitor their temperatures daily, as soon as this rises you isolate them before they begin to shed
what are the clinical signs of persistent strangles that has been present for more than a week?
purulent nasal discharge
lymph node enlargement and purulent discharge
retropharyngeal LN swelling
what do ruptured strangles abscesses of the retropharyngeal lymph nodes cause?
guttural pouch empyema
what can guttural pouch empyema from strangles lead to?
chondroid formation
why do we avoid cutting into the guttural pouch externally to remove chondroids from strangles?
carotid arteries, veins, cranial nerves (all of them easily damaged)
what are some possible complications of strangles?
cellulitis and local tissue damage
pneumonia and abscessation
immune mediated myositis/myocarditis
purpura haemorrhagica (vasculitis, type II hypersensitivity)
metastatic abscesses (bastard strangles)
where can you take a sample from to PCR for strangles?
nasopharyngeal swabs/lavage
guttural pouch wash/aspirate
aspirate from abscess
how can you confirm a horse is free from strangles?
nasal swabs - 3 negative in a week for 3 weeks
guttural pouch wash - one needed
what treatment is used for strangles?
symptomatic - NSAIDs, soft/wet food…
flush abscesses
tracheostomy if in respiratory distress
are antibiotics indicated for strangles?
not if an abscess is developing in the lymph nodes as it slows its maturation
give in outbreak when monitoring temperature (give on onset of pyrexia)
what is the best antibiotic to use for strangles?
penicillin
what is the best way to prevent strangles?
quarantine
what effect do the strangles vaccines have?
reduction of clinical signs and complications
what is inflammatory airway disease?
mild/moderate equine asthma (with slight infectious component)
what factors relating to the oxygen pathway contribute to the successful performance of the equine athlete?
gas exchange
haemoglobin concentration
heart size
skeletal muscle properties
is anaerobic or aerobic respiration faster at making energy?
anaerobic (aerobic is cleaner)
is anaerobic or aerobic respiration more efficient?
aerobic
how fast can horses reach VO2max?
20 seconds (compared to 2 minutes in humans)
what is VO2max?
the maximal aerobic metabolic rate (closely related to performance ability)
does aerobic or anaerobic respiration contribute more in an exercising horse?
aerobic dominance
what is the primary function of the respiratory system?
gas exchange
what are the secondary functions of the respiratory system?
humidification, filtering, warming air
thermoregulation
phonation and olfaction
acid-base regulation
blood filtering and defence mechanism
what does tidal volume times breaths/minute equate to?
minute ventilation
what is anatomical dead space in the respiratory system?
anything where gas exchange isn’t happening - trachea, bronchus, non-perfused alveoli
what does the rate of diffusion of gas into blood depend on?
pressure gradient
thickness of alveolar capillary barrier
why does the horse have a very thick alveolar capillary barrier?
due to extremely high pressure in the pulmonary capillaries
what three factors increase removal of oxygen from blood into the tissue?
increased temperature
decrease pH
increased carbon dioxide
how is horses breathing described?
they are obligate nasal breathers
how much does the minute ventilation increase in an exercising horse?
massively (from 80L/min at rest to 1800L/min)
how is ventilation increased during exercise?
increased tidal volume, frequency and decreased physiological dead space
how is diffusion of gases increased during exercise?
increased gradient and blood flow
hypercapnia, acidosis and hyperthermia
how can a horse increase its oxygen carrying capacity?
contracts its spleen to increase haemoglobin concentration
how is respiration and stride linked?
expire when feet hit the floor (pressure on diaphragm)
inspire when feet off the floor
what factors can decrease pulmonary gas exchange?
increased pulmonary resistance
decreased alveolar/pulmonary compliance
dynamic airway collapse
respiratory muscle/chest wall disease
decreased cardiac output
decreased haemoglobin
what is exercise induced pulmonary haemorrhage?
haemorrhage into the airway that occurs in horses that are exercising at high intensity
when does EIPH become epistaxis?
EIPH - just one nostril
epistaxis - both nostrils
what is used to diagnose EIPH?
endoscopy post exercise
how does EIPH present on the lung on post mortem?
blue discolouration to caudal lung due to haemosiderin pigment
how is grade 1 EIPH defined?
flecks of blood extending less than a quarter of the tracheal length
what is grade 2 EIPH defined as?
continuous stream of blood extending at least one half of the tracheal length
how is a grade 3 EIPH defined?
multiple streams of blood covering more than one third of the tracheal surface
what is a grade 4 EIPH defined as?
pooling and abundant blood covering the tracheal surface
what are some possible causes of EIPH?
extremely high vascular pressure
high inspiratory pressure
inflammation
locomotory shockwaves
how does the prevalence of EIPH change with age?
increases as the horse gets older
does EIPH effect performance?
grade 1 and 2 do not (doesn’t effect welfare either)
grade 3 and 4 are associated with poor performance (welfare concerns)
why does EIPH lead to inflammation?
blood is removed slowly - initially neutrophils dominate but then macrophages get involved
how is EIPH treated?
rest and anti-inflammatories
what is the only agent proven to reduce EIPH?
fireside - reduces blood volume and pressure
what is inflammatory airway disease and recurrent airway obstruction (heaves) now known as?
equine asthma
what can cause allergic asthma?
holds, bacteria/endotoxins, mites, plant debris, inorganic dust, noxious gases
what is the mediator of equine asthma after the particle enters the airway?
inflammatory mediator release
what effects does the release of the inflammatory mediator due to an allergic particle entering the airway have? (equine asthma)
increase blood flow and vascular permeability (oedema…)
airway smooth muscle tone increases
cell accumulation/activation
increased mucus production
neural reflex mechanisms increase
antibacterial activity
what receptors are activated on the smooth muscle by the inflammatory mediators?
muscarinic receptors (bronchoconstriction)
what receptors are inhibited on the smooth muscle by the inflammatory mediators?
beta2 adrenergic receptors
what contributes to the narrowing of airways in equine asthma cases?
mucosal hyperplasia and oedema
increased mucous production and decreased clearance (mucociliary escalator)
increased inflammatory cells
(chronic - fibrosis)
how is equine asthma usually subdivided?
mild-moderate
severe
what age is severe asthma seen in?
horses older than 5 year
what are the clinical signs of mild-moderate asthma?
occasional coughing and poor performance - usually seen at exercise
how long does mild-moderate asthma last for?
often self limiting with reoccurrence low
what four things occur in cases of chronic asthma?
mucus plugging
smooth muscle hypertrophy
epithelial cell hyperplasia
peribronchiolar fibrosis
what does mucus plugging, smooth muscle hypertrophy, epithelial cell hyperplasia, peribronchiolar fibrosis causes to happen in the lung/airway?
airway remodels and lung function becomes progressively impaired
what clinical signs are associated with severe asthma that has been going on for some time?
tachypnoea, increased expiratory effort, cough, nostril flare and discharge
is the dyspnoea associated with severe asthma inspiratory or expiratory?
expiratory
what does the increased expiratory effort from severe equine asthma cause?
heave line
what is found when the airway of a horse with equine asthma is endoscopes?
excessive mucous
when airway cytology is carried out on a horse with equine asthma, what is found?
increased neutrophils and eosinophils
is it best to use a tracheal aspirate or bronchoalvelar lavage to diagnose equine asthma?
BAL
what percentage neutrophils on a BAL would correlate with a horse having equine asthma?
> 25%
what is the most common adventitious respiratory sound caused by URT stenosis?
inspiratory wheeze
what are the three factors used to treat equine asthma?
environmental control
corticosteroids
bronchodilators
what is the aim of environmental control to manage equine asthma?
reduce respirable particles (dust, moles, fungi…) - increase airflow and time outside
what form of asthma is it difficult to control using environmental management?
summer pasture associated pulmonary disease (allergy to pollen…) - get worse when turned out
how can feed be managed to control equine asthma?
wet concentrates
eat from floor
(feed wetter foods)
how can housing be managed to control equine asthma?
remove horse around mucking out
put them outside
low dust bedding
no deep litter system
consider other horse stables
what effects do corticosteroid have to control asthma?
reduce cell accumulation/activation
reduce vascular changes
reduce bronchoconstriction
what systemic corticosteroids can be given for equine asthma?
prednisolone
dexamethasone
how can corticosteroids be administered for controlling asthma?
topically (inhaled)
systemically
what types of drugs can be used as bronchodilators for equine asthma?
beta2 adrenergic agonists
muscarinic antagonists
what are the indications for using bronchodilators in asthma cases?
emergency (rescue) therapy in flare up
before other inhaled medication
before exercise
what are some beta2 agonists used as bronchodilators?
clenbuterol
salbutamol
salmeterol
what are some muscarinic antagonists used as bronchodilators?
atropine
buscopan
ipratropium bromide (inhaled)
what are dembrexine and saline nebulisation used for in asthma cases?
mucolytics (soften mucous)
what lung lobes are most effected by bacterial colonisation?
right ventral lobes
what are the clinical signs of bronchopneumonia?
dyspnoea (tachypnoea), systemic illness, adventitious lung sounds, cough
what are the clinical signs of pleuropneumonia?
reduced ventral lung sounds and dull on percussion
what are the three stages of pleuropneumonia?
acute exudative stage
fibrinopurulent stage
organisational stage
what happens in the acute exudative stage of pleuropneumonia?
inflammation of lung/pleura produces a sterile protein rich pleural exudate
what happens in the fibrinopurulent stage of pleuropneumonia?
bacteria invade and multiply in pleural fluid and fibrin is deposited on the pleural surface
what is used to treat broncho/pleuralpneumonia?
broad spectrum antibiotics - penicillin, gentamicin, metronidazole
anti-inflammatories
supportive therapy
is the equine lungworm called?
Dictyocaulus arnfieldi
what conditions has to be met for a horse to get lungworm?
must cograze with donkeys (donkeys are asymptomatic carriers)
what is used to treat equine lungworm?
ivermectin
what is equine multi nodular pulmonary fibrosis associated with?
EHV 5
