Coughing in horses Flashcards
DDx fore coughing - foals and weanlings
URT disease: EHV1 and 4, EIV, Strep. equi equi
LRT disease: EHV 1&4, EIV, undifferentiated respiratory tract infection, Strep. zooepidemicus, Rhodococcus equi, Strep equi equi, Parascaris Equorum
What is the most common cause of pneumonia in foals and weanlings?
BACTERIA - Strep zooepidemics (UK) and Rhodococcus equi (USA) most commonly. Also Actinobacillus, Klebsiella, Staph aureus, Bordatella, Mycoplasma
CS - infectious pneumonia - weanling - 3
+/- auscultable changes
Mild pyrexia
Cough
How to make a diagnosis - weanling bacterial pneumonia
History, CS, further diagnostic tests:
- ) Endoscopy - mucopurulent exudate in trachea
- ) Radiography - bronchointerstitial pattern
- ) Cytology (BAL or tracheal aspirate) - increased degenerate neutrophils and intracellular bacteria
How is inflammatory non-infectious disease different to inflammatory infectious disease?
INFLAMMATORY NON-INFECTIOUS: non-degenerate neutrophils, no bacteria
INFLAMMATORY INFECTIOUS: degenerate neutrophils, intranuclear bacteria
DDx- coughing - adult horses
INFECTIOUS versus NON-INFECTIOUS
List infectious causes of adult horse coughing
URT disease: EIV, EHV1&4, EVA, ERV, Strep equi equi
LRT disease: EIV, EHV1&4, ERV, Strep zooepidemicus, Strep pneumonia, Pasteurella/actinobacillus, Strep equi equi
Epidemiology - URT versus LRT disease as coughing in adult horses
- +URT: less common that LRT, mainly young horses (1-2 years)
- LRT: common in all racing age groups (esp 2yo flat yards and 4yo in NH yards)
- Bacterial > viral (both can occur in combination
CS - infectious cause of coughing - adult horses
- URT: fever, nasal discharge, coughing, enlarged submandibular LNs
- LRT: fever, nasal discharge, coughing, mucoid tracheal secretion, +/- haemorrhage, poor performance
- May be subclinical
Site of latency for EHV1&4? 3
Bronchial LNs
Submandibular LNs
Trigeminal ganglia (i.e. CNS)
What causes ENH reactivation?
Stress
EHV2 possibly
Sequence of events to be determined
When are horses exposed to EHV1&4?
Foals and weanlings
Source = lactating mares or foal to foal
Immunity to EHV?
Short lived (3-5 months) so become reinfected (breeding or racing career) via respiratory secretions, fomites or aborted material. Vaccine can’t improve immunity rate. Re-exposure usually causes mild or inapparent infection (except broodmare where it causes abortion in the last trimester).
Pathogenesis - EHV1&4
EHV1&4 inhalation. Incubation 3-7 days. Replicates in URT epithelium. EHV-1 only then disseminates to LRT. Transported to other organs in T lymphocytes. Viraemic for up to 3 weeks. Vasculitis – neurological disease, abortion, chorioretinopathy. May be accompanied by secondary bacterial infection. May be subclinical.
What age of horses does EIV usually affect?
most commonly racehorses 2-3yo. worldwide occurence (except Australia and NZ)
Spread - EIV
Highly infectious, spreads by aerosol for distances of >30m. Spreads rapidly through susceptible populations. Spread by inhalation.
Vaccine - EIV
Vaccinated animals are susceptible to infection within 2-3 months. Partial immunity may suppress CS but allow virus shedding.
What does EIV infect? What does this lead to?
epithelial cells or URT and LRT –> laryngitis, tracheitis, bronchitis and bronchiolitis –> loss of ciliated epithelium, compromised mucocillary mechanism. May be associated with secondary bacterial infection.
T/F: EIV has no viraemia.
True - there are no CS reflecting other organs. Diagnosis is ONLY possible via respiratory secretions.
Outline bacteria that cause LRT infection in adult horses
Strep. zooepidemicus
Strep pneumoniae
Pasteurella/actinobacillus
Inhaled and overcome defence mechanisms –> LRT signs only. May occur secondary to viral infection OR non-infectious airway disease.
How can a respiratory infection be identified? adult horses
URT: clinical signs (viruses only)
LRT: clinical signs/loss of performance, Endoscopy and LRT samples (mucous, increases in degenerate neutrophils), Haematology (neutropaenia early, neutrophilia late, lymphopaenia early, lymphoctyosis late, hyperfibrinogenaemia marker of inflammation)
How can EHV1&4 be definitively diagnosed?
VIRUS ISOLATION: blood (30mls, heparinsied), nasopharyngeal swab (PCR).
SEROLOGY: paired samples (10-14d apart)
How can EIV be diagnosed?
SEROLOGY - paired samples, 10d apart,
VIRUS ISOLATION (weeks)
PCR (quicker)
ELISA (quicker) vs. nucleoprotein from nasopharyngeal swab
treatment - viral infection
Isolate. Symptomatic and supportive. Limit stress. Maintain hydration. NSAIDs (limit pyrexia and improve appetite). REST. Specific anti-viral therapy (Acyclovir or IFN). Monitor for secondary infection.
Treatment - bacterial infection
**AB and rest **
Also if not improving with the above, improve environment, dust free management, anti-pyretics, mucolytics, bronchodilators
Are vaccines available for the current bacterial respiratory pathogens in horses?
No
Outline EIV vaccination
Present-day threat is from H3N8 Equi-2 Florida strains which are divided into Clades 1 and 2. But vaccines are effective against H7N7 and H3N8. There may be some cross-protection and the adjuvants have a significant effect on increasing immune responses.
What are the Jockey Club rules for EIV?
1st EIV vaccination
2nd = 21-92 days later
3rd = 150 to 215 days from 2nd vaccination. Thereafter annually with the last permissible day being the same date as the previous year’s vaccination. Horses may not race until the 8th day after the day of vaccination.
How do the FEI rules relate to the Jockey Club?
As for the Jockey club except since 2005, they require a booster within 6 months and 21 days of the competition/
Outline EHV-1 and 4 vaccination
Short-lived immunity (likewise natural infection)
Strains are Ag distinct and variation between strains
May not stimulate adequate CMI and mucosal immunity.
TYPES: modified live or inactivated. Both reduce clinical disease, nasal shedding and days of viraemia.
List 3 common non-infectious causes of coughing in adult horses
RAO
SPAOPD
IAD
List fairly common causes of non-infectious coughing in adult horses - 6
- aspiration pneumonia
- pleuropneumonia
- pulmonary abscesses
- left-sided heart failure
- epiglottic entrapment
- URT foreign body
List uncommon causes of non-infectious coughing in adult horses
- TB
- lungworm
- tracheal stenosis/collapse
- inhalation pneumonia
- interstitial pneumonia
- neoplasia
List other names for RAO - 3
Recurrent airway obstruction; COPD, Heaves, Broken Wind
Define RAO.
What are it’s 3 features?
naturally occuring lower airway disease characterised by periods of reversible airway obstruction. Lifelong condition. Genetic component.
3 features are neutrophil accumulation, mucous production and bronchospasm.
Pathogenesis - RAO
Spores and allergens deposit in bronchioles –> type 1 immune reaction (MC degranulation), type 3 (immune-complex) and type 4 (delayed). All result in bronchosconstriction, mucous production and airway inflammation. Tissues are primed and can become hypersensitive and respond to non-specific allergens.
Acute signs - RAO
Increased RE
Double expiratory effort/dyspnoea
Chronic signs - RAO
varies in severity (poor performance - overt signs of respiratory dysfunction +/-coughing and hypertrophy of the abdominal wall mm)
Dx - RAO
- Likelihood determined by Hx and PE
- Then assess airway inflammation (TTW or BLAV via endoscopy) and rule out bacterial pneumonia.
- Measure function impairment - radiography, ultrasound, response to treatment
How can you pathologically assess airway inflammation?
Tracheal aspirate via endoscope
Transtracheal aspirate
BAL
What would you see on clinical pathology in RAO? 3
- increased cellularity (predominantly non-degenerate neutrophils)
- increased mucous
- Curshmann’s spirals (thick mucous/cellular casts from obstructed small airways)
What are the 4 main areas for RAO tx?
- ) environmental management
- ) reversal of bronchoconstriction
- ) decreased pulmonary inflammation
- ) decreased mucous accumulation
What does SPAOPD stand for? What is the treatment?
= Summer Pasture Associated Obstructive Pulmonary Disease.
Tx = as for RAO except for environmental allergens as the allergens are pasture-based so affected animals should be stabled (dust free).
What does IAD stand for?
Inflammatory Airway Disease
Which horses get IAD?
Typically seen in young performance horse (prevalence 20-65%). Also in older NH, SB racehorses and sports horses.
Characteristics - IAD
excessive mucous in airways
cough and/or reduced performance
FREQUENTLY SUBCLINICAL
Cause - IAD - 5
Definitive cause unknown, following are implicated:
BACTERIA - S.zooepidemicus, S.pneumoniae, Actinobacillus, Mycoplasma
VIRAL - not associated with EHV or rhinovirus
BLOOD FROM EIPH - causes inflammation and/or secondary infection
INHALED DUSTS, LPS, AMMONIA
COMBINATION OF ABOVE.
Diagnosis - IAD
Based on endoscopy to visualise tracheal mucous AND cytological examination of the tracheal aspirate/BAL (would show increased mucous, increased neutrophils or eosinophils/MCs)
Treatment - IAD - 6
- Environmental changes to reduce dust
- ABs
- IFN
- Corticosteroids – systemic or inhaled
- Sodium chromoglycate
- Omega-3 polyunsaturated fatty acid supplementation
What are the similarities/differences between RAO and IAD?
Share many similarities. Differences involve severity of airflow limitation and inflammation. IAD horses do NOT show respiratory difficulty at rest. Are they really different disease? Are they a spectrum of the same disease? Many horses have features of both. Not all IAD horses go on to have RAO.
Similarities/differences in clinical signs for RAO and IAD?
BOTH - cough, exercise intolerance, tracheal mucus
IAD = normal auscultation, crackles, wheezes possible, NO respiratory difficulty at rest. RAO = crackles and wheezes usually present, episodes of respiratory difficulty at rest
