Lower respiratory tract disease in groups of horses Flashcards
What are some infectious respiratory diseases in horses?
- Influenza
- Equine herpes virus 1+4
- Rhodococcus equi
- Streptococcus equi var equi
When would you suspect infectious respiratory disease?
- Bilateral nasal discharge (unilateral usually in front of nasal septum + non-infectious)
- Pyrexia
- Cough, enlarged lymph nodes, anorexia
- Individual vs group affected
- Vaccine Hx
- Travel Hx
How would you confirm infectious disease?
- Culture / PCR / virus isolation
- Antibodies (ELISA)
What is the pathogenesis of influenza?
- Aerosol transmission (direct / indirect)
- Enters URT + replicates
- Viraemia
- Destroys mucocilliary tract
- secondary pneumonia
What is the epidemiology of influenza?
- Spread up to 1-2km (8km in wind)
- V short incubation
- Low mortality
- Vaccination not 100% effective
What is the most common strain of influenza?
- H3N8
What are typical clinical signs of influenza?
- Pyrexia
- Harsh dry cough
- Nasal discharge - serous initially, mucopurulent with 2ndary bacterial infection
- Submandibular LN may be normal
- Milder in vaccinated animals
How is influenza diagnosed?
- Nasopharyngeal swab - RT-PCR
- Serum sample - antibody titre
How would you treat influneza?
- Supportive care
- NSAIDs
- Anti-microbials if 2ndary infection
- Rest for 2 weeks minimum
- Vaccinate in face of outbreak
How would you control influenza?
- Isolate
- Movement restrictions
- Biosecurity - quarantine + disinfection
- Vaccination
Why would a vaccine not be effective?
- Strain
- Timing - Ab dip towards end of vaccine lifespan
- Uptake
- ‘non-responders’
What are the different types of equine herpes virus?
- EHV-1 : Respiratory disease, neurological disease, abortion (sudden death in foals).
- EHV-2 : Keratoconjunctivitis
- EHV-3 : Equine Coital Exanthema
- EHV-4 : Respiratory disease (& abortion)
- EHV-5 : Equine Multinodular Pulmonary Fibrosis
What is the pathogenesis of EHV 1+4?
- aerosol spread (direct / indirect)
- nasal inoculation + replication in URT epithelium
- EHV 4 = local infection (rhinopharyngitis/ tracheobronchitis)
EHV 1 = migration to systemic infection - viraemia, vasculitis, microthrombosis + infarction, ataxia + abortion
- Latency = carriers for life
What are clinical signs of EHV 1+4?
- Respiratory - EHV4 more common in respiratory outbreaks
-biphasic fever (mild)
-bilateral nasal discharge - enlarged submandibular LNs
- +/- cough
- Abortion / stillborn / neonatal death
- Neuro disease (EHV 1)
How is EHV diagnosed?
- Nasal swab - PCR / virus isolation
- Blood samples - check WBCs
- PM
How is EHV treated?
- No Tx required
- Rest
- NSAIDs?
How is EHV controlled?
- Reduce shedding + exposure
- Vaccination + biosecurity
- do not vaccinate in outbreak
What is the pathogenesis of Rhodococcus equi?
- Nasal inoculation - replicates in infected alveolar macrophages
- Causes pyogranulomatous bronchopneumonia
- Shed in respiratory secretions + manure
What is the epidemiology of r. equi?
- Most common cause of pneumonia in foals (<2w/o)
What are clinical signs of R.equi?
- Pulmonary - multifocal pulmonary abscesses, high RR + pyrexia
- Extra-pulmonary - uveitis, septic arthritis, IMPA, enterocolitis, abscessation anywhere
- General - weight loss, poor growth rates
How is R. equi diagnosed?
- Farm history
- Bloods - generalised inflammation
- Ultrasonography - score lesions (only treat if over 10 lesions >1cm)
- Radiography
- Transtracheal aspiration - cytology
How would you treat R.equi?
- Don’t treat every foal - sub-clinical will resolve
- Macrolide + rifampin
Whats important about macrolide use?
- Fatal colitis in mares - only use in foals
- Wipe foals muzzle after tx + keep in shade
How would you control R.equi?
- Administer R.equi hyperimmune plasma to foals
- NO vaccines
- Reduce stocking density
What are clinical signs of Strep. equi?
- Pyrexia + inappetence (24-48hrs)
- Bilateral mucopurulent nasal discharge
- Lymphadenopathy
- LN abscessation
- Dyspnoea
- Dysphagia
- lead to bastard strangles, purpura haemorrhagica, myositis
How is Strep equi diagnosed?
- identify active disease
- Nasopharyngeal swabs - PCR + culture
- GP lavage (>48hrs) - PCR + culture
- Aspiration of LN abscess - PCR + culture
How is Strep equi diagnosed? - identify carriers
- Nasophanryngeal swabs - 3 times 1 week apart - PCR + culture
- GP lavage - gold standard - PCR + Culture
How is strep equi treated?
- Penicillin
- NSAIDs
- Supportive Tx
- Lance abscess
- Tracheostomy if severe dyspnoea
How would you control strangles?
- Early isolation of pyrexic animals
- Traffic light system - exposure risk
- Yard closed until clear
- Biosecurity
- 3 weeks after active cases identify carriers / PI
How would you prevent strangles?
- Yard strategy
- Biosecurity
- Quarantine
- Isolate
- Vaccine? doesn’t work too well - consider for high risk
What is the 2nd most common cause of poor performance after muscoskeletal?
- Mild asthma / inflammatory airway disease
- prevalence - 11-50% based on mucopus in trachea
What are risk factors for mild-asthma?
- Co-mingling
- Exercise - strenuous exercise
- Transport
- Age - young
- Stable environment - poor ventilation + bedding
