Approach to the coughing horse

What are the clinical signs of respiratory disease?

cough- specific indicator

nasal discharge ± lymph node enlargement

alterations in rate, pattern or effort of respiration

respiratory noise

altered airflow at nostrils

poor performance

weight loss

What is the diagnostic approach to a coughing horse?

detailed history provides vital info

routine examination

provisional diagnosis

therapeutic trial- management, medication

further investigation if required

prognosis

What are important signs to find out about during a history?

cough

nasal discharge

changes in respiration- dyspnea/increased effort

poor performance- progressive loss?, prolonged recovery time?, epistaxis at exercise?

systemic signs- pyrexia, inappetence, weight loss

What is important extra info to find out about a cough?

duration, frequency

character

nasal discharge at any stage

cough related to feeding

cough related to exercise

cough related to stabling

eating and drinking normally

dewormed recently

in contact with donkeys

What is important extra info to find out about nasal discharge?

duration

quantity increasing or decreasing

unilateral or bilateral

clear, mucoid, purulent, or bloody

malodorous

related to feeding or head posture

any change in facial contours

associated cough

What is important extra info to find out about dyspnea?

normal at rest?

if only at exercise, what speed does is occur

nasal discharge or cough

if apparent at rest is it related to housing

seasonal?

worsened by feeding?

What are respiratory signs to find out about during history?

duration- infection vs allergic cause

health of individual- previous episodes?

recent travel

health of cohorts

environment and seasonality- changes in management, severe equine asthma

Why is the breed important to find out about?

idiopathic tachypnea of clydesdale foals

laryngeal disease less common in ponies

miniature horse/pony: tracheal collapse

mild-moderate equine asthma: thoroughbred and standardbred

What should you observe about the environment?

mucopus on floor

bedding/forage

location of forage and bedding storage/muck heap

ventilation

What should of observe about the horse before you start clinical exam?

breathing at rest

rate- 8-16 breaths per min

pattern regularity

increased effort?

What could cause rapid deep breaths?

respiratory distress

may be caused by hypoxemia due to cardiorespiratory compromise

severe anemia

hypovolemia

endotoxemia

What could cause rapid shallow breaths?

pain

particularly pleural pain

What could cause slow deep breaths?

underlying pathology such as severe equine asthma

What are signs of upper respiratory tract obstruction during clinical examination?

predominately inspiratory

often associated with noise ie stertor or stridor

severe trauma/swelling/edema of head/nasal passages

pharyngeal obstruction

severe laryngeal dysfunction

What should you check during clinical examination of the head and neck?

nasal discharge- color, volume, uni or bilateral odor

uniform air movement at nostrils

lymph nodes- submandibular and retropharyngeal

swellings/asymmetry of head

eyes- conjunctiva, epiphora, nasolacrimal duct

tracheal palpation and sensitivity

URT noise

What are differential diagnosis of epistaxis at rest?

guttural pouch mycosis

ethmoidal hematoma

nasal polyp

What is ddx for epistaxis after exercise?

exercise induced pulmonary hemorrhage

What is ddx of epistaxis after trauma?

sinus hemorrhage

ethmoidal: post nasogastric intubation

Where do you auscultate during a thoracic auscultation?

palpation of thorax

lung fields- both sides

trachea

What are you assessing on thoracic auscultation?

audibility and distribution of breath sounds

are adventitious sounds audible- wheezes, crackles, or friction rubs

What is a rebreathing test for?

exacerbation of lung sounds

always use if nothing abnormal on normal ausculation

no need if abnormal sounds at rest, avoid if severely dyspnoeic

accentuates focal pathology or mucus accumulation in small airways

What are the alterations in density of intrathoracic structures during thoracic percussion?

normal lung- resonant

pneumothorax- hyper-resonance

pleural effusion/lung infiltration- dull

if pain, consistent with pleuritis

What are ancillary diagnostic tests?

infectious disease sampling- nasopharyngeal swab

endoscopy

lower respiratory tract sampling

ultrasonography

thoracocentesis

radiology

Could be infectious respiratory disease if they answer yes to any of which questions?

pyrexia?

is the horse unwell?

enlarged lymph nodes?

other animals affected?

What viral respiratory disease should you consider?

equine influenza A

equine herpes virus types 1 & 4

equine rhinitis virus

equine adenovirus

equine viral arteritis

What are characteristics of acute disease from streptococcus equi (strangles)?

highly contagious- particularly young

entry via nose or mouth

pyrexia, pharyngitis and then lymph node abscessation

often not treated with antimicrobials

most abscesses rupture, followed by a full recovery

What happens in carrier state (and chronic disease) of streptococcus equi?

retropharyngeal lymph nodes can rupture pus into guttural pouch

a proportion of horses fail to clear this pus and become ‘carriers’

many possible complications/chronic disease post infection

How do you sample streptococcus equi?

aspiration and culture from abscessed lymph nodes

nasopharyngeal swab (or lavage)- bacterial culture and PCR

guttural pouch lavage- bacterial culture and PCR

serology

How do you sample for viral respiratory disease/

nasopharyngeal swab- virus isolation/culture, PCR, ELISA

serology

What is the pathogenesis of equine influenza?

neuraminidase glycoproteins break down mucocilliary protection giving viral access to underlying epithelial cells

hemaggultinin glycoproteins is then responsible for viral attachment to host cells

replicate in respiratory epithelial cells

cell necrosis and desquamation- irritant receptors exposed

impaired ciliated clearance system

norma architecture takes 6 weeks to recover

What is the epidemiology of equine influenza?

high morbidity (low mortality)

respiratory transmission- direct or indirect contact

occurs worldwide

reduced morbidity/severity with improved immune status- ie prior infection or vaccination

What are clinical signs of equine influenza?

short incubation period 3-5 days after virus exposure

extreme pyrexia 39-41 degrees C

upper respiratory tract signs- serous or mucopurulent nasal discharge, may see lymphadenopathy

anorexia and depression

How do you diagnose equine influenza?

history and clinical signs

viral detection

serology- not all will serconvert

viral culture and isolation- nasopharyngeal swabs (least sensitive)

real time PCR detection - nasopharyngeal swab- early in clincial course but if late consider swabbing in contacts

rapid antigen detection tests- nasopharyngeal swab, useful in epizootic

What is the treatment for equine influenza?

prompt isolation of affected and all contacts

symptomatic

minimize stress and prolonged rest- if severe, up to 50-100 days

antibiotics if suspect secondary bacterial infection

vaccination

How do you prevent and control equine influenza?

effective boundaries between equine premises

avoid single air spaces in stables

prolonged journey risk factor for horses in UK

HBLB operates a surveillance scheme

mandatory racehorse vaccination since 1980 in UK and USA

What does OIE recommend for vaccines?

should contain both clade 1 and clade 2 viruses of the Florida sublineage

What are the BHA rules on influenza vaccination regimen?

first vaccination- influenza and tetanus

1 month later, second vaccination- influenza and tetanus

5 months later, third vaccination- influenza

6 months later, 6 monthly boosters, influenza and tetanus every 2 to 3 years

What kind of immunity do horses get from equine herpes virus?

short term

prone to repeat infections

What might immuno-suppression of equine herpes virus lead to?

reactivation

from corticosteroids, ‘stress’, transport, husbandry

What are clinical signs of EHV 1 and 4?

similar to EI (less severe)

less marked cough

severity depends on age, immune status, strain, dose

sub-clinical infections- especially in older horses

slow rate of viral spread

EHV1 respiratory signs can be superseded by abortion, neurological disease

How do you diagnose EHV 1 and 4?

serology

virus isolation

PCR

How do you manage and control EHV 1 and 4?

vaccination- diff regimens for respiratory prevention vs abortion

management principles similar to EI

avoid contact with broodmares

What are ancillary diagnostic tests for infectious respiratory diseases?

infectious disease sampling- nasopharyngeal swab, serology

endoscopy

lower respiratory tract sampling- tracheal wash, bronchoalveolar lavage

ultrasonagraphy

thoracocentesis

radiology

What are viewing on endoscopy?

visualize normal/anatomical abnormalities

nasal passage

ethmoid turbinates

sinus drainage angle

pharynx and larynx

guttural pouches

trachea and carina

proximal bronchi

What grade of tracheal mucus has clinical significance?

1-5

they are associated with poor athletic performance