Coughing in Horses Flashcards by Adam Northwood

Differential diagnosis for coughing in foals and weanlings (URT)

EHV 1/4
Equine influenza
Streptococcus equi equi

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Differential diagnosis for coughing in foals and weanlings (LRT)

EHV 1/4
Equine influenza
Undifferentiated resp tract infection
Rhodococcus equi
Streptococcus equi equi
Parascaris equorum

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What are the causes of undifferentiated bacterial pneumonia in horses…

Streptococcus zooepidemicus

Actinobacillus, Klebsiella, Staph aureus, Bordetella, Mycoplasma

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What are the clinical signs of undifferentiated bacterial pneumonia?

Auscultable changes
Mild pyrexia
Cough
Usually bright and hapy

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How can you diagnose undifferentiated bacterial pneumonia in horses?

History
Clinical signs
Diagnostic tests:
- Mucopurulent exudatein trachea on endoscopy
- Bronchointerstital pattern on radiography
- BAL/tracheal aspirate
+ Degenerate neutrophils increased, intracellular bacteria

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What is the treatment for undifferentiated bacterial pneumonia in horses?

ABs on C+S
Rest
Dust free environment

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Differentials diagnosis for infectious causes of coughing in adult horses (URT)?

Equine influenza
EHV 1/4
EVA
Equine Rhinitis Virus
Streptococcus equi equi

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Differentials diagnosis for infectious causes of coughing in adult horses (LRT)?

Equine influenza
EHV 1/4
Equine Viral Arteritis
Equine Rhinitis Virus
Streptococcus equi equi
Streptococcus zooepidemicus
Streptococcus pneumonia
Pasteurella/actinobacillus

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How does infection spread between URT and LRT?

Causes of URT infections always start there then spread to LRT

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Epidemiology of upper airway disease (infectious)

Less common that lower airway
Mainly young horses, then get some form of immunity
Usually caused by viruses

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Epidemiology of lower airway disease (infectious)

Common in racing age groups
Seen in all ages
Bacterial infection more common but can occur in combination

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What are the clinical presentation of upper respiratory tract infection in horses?

Fever
Nasal discharge
Coughing
Enlarged LNs
Dull and depressed

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Clinical presentations of lower respiratory tract infections in horses?

Coughing
Mucoid tracheal secretions
Poor performance
May be subclinic
\+/- fever
\+/- nasal discharge

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How prevalent is EHV 1+4 in the UK?

Endemic in the UK

75% of horses have latent infection acting as reservoir

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What may activate a latent EHV1/4 infection?

Stress
Transport
Other illness
Vaccinations

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Epidemiology of EHV 1&4

Site of latency
First exposure
Immunity
Re-infection
How serious?

Site of latency:
Bronchial LN
Submandibular LN
Trigeminal ganglia

EHV2 may be involved in reactivation

First exposure as foals and weanlings

Source of infection lactating mare (stress due to pregnancy)
Foal to foal spread

Immunity short lived (3-5 months)
Vaccination ineffective

Re-infected during breeding or racing careers
Respiratory secretions, foetus/placenta, fomites

Re-exposure usually causes mild or inapparent infection

Except in broodmare (abortion last trimester if infected when pregnant)

Also get neurologic disease

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Pathogenesis of EHV1

1) Inhalation of virus
2) Incubation 3-7 days
3) Replicates in URT epithelium (URT signs)
4) Disseminated to LRT (LRT signs)
5) Transported to other organs in T lymphocytes
6) Viraemic up to 3 weeks
7) Vasculitis
- Neurological disease
- Abortion
- Chorioretinopathy (damage to retina)
8. May be accompanied by secondary bacterial infection

(May be subclinical)

Pathogenesis of EHV4

Inhalation of virus
Incubation 3-7 days
Replication in URT (URT signs)
Disseminated to LRT (LRT signs)

Epidemiology of equine influenza virus

2-3yr old racehorses
H3N8
Worldwide
Antigenic drift (not shift)
Most common cause of URT infection
Aerosol and direct contact spread
Vaccinated animals susceptible to infection within 2-3 months
Partial immunity may suppress clinical signs but allow shedding

How can you diagnose lower airway infection in horses?

Clinical signs/loss of performance
Endoscropy and LRT samples
Mucopus
Degenerate neutrophils
Haematology
Neutropaenia(early)/neutrophillia(late)
Lymphopaenia(early)/lymphocytosis(late)
Hyperfibrinogenaemia
Imaging not very useful

How can you identify specific respiratory pathogens in the horse?

a. Bacteria
b. Viruses

a. Culture and cytology of LRT samples

b. Rarely performed (treatment is the same for all)

Diagnosis of EHV1&4?

Virus isolation
Blood
Nasopharyngeal swab and PCR to looks for bits of viral DNA

Serology
Paired samples

Diagnosis of equine influenza?

Serology
Paired samples 14 days apart

Nasopharyngeal swab
Virus isolation (not from blood)
PCR

Treatment for viral respiratory infection in the horse?

Isolate
Symptomatic and supportive
Limit stress
Maintain hydration
NSAIDs to limit pyrexia and improve appetite
REST
(Specific antiviral therapy too expensive)
Monitor for secondary infection

Treatment for respiratory bacterial infection in the horse?

``` Antibiotics Rest Dust free environment Anti-pyretics Mucolytics Bronchodilators ```

Describe equine influenza vaccination..

Start >6months due to maternal anitbodies 1. 1st vaccination 2. 2nd vaccination 21-92 days from 1st 3. 3rd vaccination 150-215 days after second 4. Therefore annually 5. Horses can't race until 8th day after vaccination

Describe EHV1&4 vaccination...

``` Can vaccinate from 4 months Natural immunity short lived (unlikely to improve with vaccination) Reduced clinical disease, nasal shedding, days of viraemia Not complete protection Not currently available in UK 2 doses 4-6 weeks apart Booster at 6 months Pregnancy = 5th,7th,9th month ```

Non-infectious causes of coughing in adult horses

``` Equine asthma Aspiration pneumonia Pleuropneumonia Pulmonary abscesses Left heart failure Epiglottic entrapment URT foreign body TB Lungworm Tracheal stenosis Neoplasia ```

What are the types of equine asthma?

Mild to moderate = IAD | Severe = RAO/SPAOPD

Describe mild-modere equine asthma...

``` Young racehorses Excessive mucous in airways May exhibit cough/reduce performance NO increased respiratory effort at rest Signs are chronic (>4weeks) Frequently subclinical ```

Pathogenesis of mild-moderate equine asthma...

``` Unknown Inhaled dusts, ammonia causes Bacterial infections Viral infections Blood from EIPH - Inflammation - Secondary infection ```

Diagnosis mild-moderate equine asthma?

Endoscopy - increased mucous Tracheal aspirate/BAL - increased mucous, neutrophils, eosinophils, mast cells

What is the treatment for mild-moderate equine asthma?

``` Environmental changes ABs Interferon Steroids Bronchodilators ```

Describe severe equine asthma...

Naturally occurring lower airway disease characterised by periods of reversible airway obstruction ``` Neutrophil accumulation Mucous production Bronchospasm Usually >7 years Life long condition ```

Pathogenesis of severe equine asthma?

1. Spores and allergens deposit in bronchioles 2. Immune reactions Type 1 (mast cell degranulation) Type 3 (immune-complex) Type 4 (delayed) 3. Bronchoconstriction 4. Mucous production 5. Airway inflammation 6. Tissues primes 7. Can become hypersensitive 8. Respond to non-specific allergens

Clinical signs of severe equine asthma? 1. Acute 2. Chronic

1. Increased respiratory effort, dyspnoea | 2. Poor performance to overt respiratory dysfunction with/without coughing and hypertrophy of abdominal muscles

How can you diagnose severe equine asthma?

``` History Physical exam Assess airway inflammation - Transtracheal wash - BAL Rule out bacterial pneumonia Evaluate response to treatment ```

How can endoscopy be used to assess airway inflammation?

``` Rules out pharyngeal disease Airway inflammation - Hyperaemia - Corina blunting Assess tracheal mucous Obtain tracheal aspirates ```

Pathogenesis of equine influenza...

1. Inhalation 2. Incubation 1-3days 3. Infects epithelial cells of URT and LRT 4. Loss of ciliated epithelium 5. URT/LRT signs 6. Associated with secondary bacterial infection 7. NO VIRAEMIA

Treatment of severe equine asthma?

Environmental management Reversal of bronchoconstriction Decreased pulmonary inflammation Decrease pulmonary mucous accumulation

Describe lower respiratory tract bacterial infection in horses...

Streptococcus zooepidemicus Streptococcus pneumoniae Pasteurella/actinobacillus Inhaled and overcome defence mechanisms LRT signs only May occur secondary to viral infection or non-infectious airway diseases