Lower respiratory tract conditions affecting Groups of horses Flashcards
Name 4 infectious respiratory diseases of horses
- Equine influenza
- Equine herpes virus 1 and 4
- Rhodococcus equi
- Streptococcus equi var equi
How can you determine if a horse has an infectious respiratory disease?
- Compatible clinical signs: groups affected, pyrexia, dull.
- Haematology, acute phase proteins
- Detection of infectious agent: culture/PCR/Virus isolation
- Detection of immune response against infectious agent: antibodies (usually ELISA)
Subtypes of equine influenza are based on?
Haemagglutinin (H) Neuraminidase (N) = glycoprotein surface antigens
Why are vaccines less able to prevent outbreaks of equine influenza?
H3N8 displays more antigenic drift
Describe the pathophysiology of equine influenza
Infection strips the cilliated epithelium from the URT so it loses the ability to defend itself
List the clinical signs of equine influenza
- Incubation period = 1-5 days (proportional to 1/virus dose)
- Fever up to 41ºC
- Cough: dry and hacking -> moist
- Oedema and hyperaemia of URT/trachea
- Nasal discharge: serous -> mucopurulent
- Lethargy, inappetence +/- muscle soreness
How long does it take a horse to recover from equine influenza?
Usually complete in 1-3 weeks unless secondary respiratory infections occur
How is equine influenza indicated from haematology results?
- Lymphopenia, neutropenia initially
- Later monocytosis, neutrophilia and hyperfibrinogenaemia
How is equine influenza diagnosed?
- Virus isolation from nasopharyngeal swabs: special handling procedures speak to the laboratory first, PCR
- Serology: rising antibody titre (4x) over 2 – 4 weeks (care: vaccination)
When in an equine influenza infection is the best time to swab?
1-5 days post infection
High antibody levels
Clinical signs present
Describe the treatment for equine influenza
- Supportive care: hydration, NSAIDs
- +/- Antibiotics for secondary bacterial infections
- Generally improve after 7-10 days
Describe resting a horse following an equine influenza infection and its importance
- Require prolonged period of rest (1 week off for every day of fever) to allow epithelium to recover
- If not rested then often develop chronic cough and persistent pharyngitis / tracheitis
Describe mortality in adult horses with equine influenza
- Very low
- Secondary bacterial (pleuro)pneumonia
- Purpura haemorrhagica
Describe mortality in foals with equine influenza
Mortality in Foals higher esp. if low immunity
- Myocarditis
- Secondary Bacterial bronchopneumonia
- Acute Respiratory Distress syndrome (ARDS) – immune system attacks lungs
Describe how equine influenza infections spread
Rapidly spread by the respiratory route especially if close direct contact:
- Coughing contributes to the spread
- Windborne virus may spread for up to 8km
- Morbidity in naive horses close to 100%
Excrete virus for up to 8 days after initial infection
- Survives in the environment for up to 36 hours but is easily killed by cleaning and disinfection
- Can be spread by Fomites
How can equine influenza outbreaks/infections be controlled?
- Difficult! Rapid spread / short incubation period
- Isolate cases in separate stable or yard (20-40 feet)
- Monitoring of all horses for pyrexia + isolation
- Separate personnel, equipment etc.
- Disinfect (Bleach, ionophor, phenol, soap)
Name the different influenza vaccines
ProteqFlu
Equip F
Describe infections of equine herpes virus 1 and 4
Become latent and reactivate under times of stress
- Shed virus
- Often subclinical
What are the 3 main consequences of equine herpes 1 infection in horses?
- Respiratory disease (and EHV4)
- Abortion
- Neurological (Equine herpes myeloencephalopathy)
What are the clinical signs of mild viral respiratory infections in horses?
DULL
+/- mild coughing, serous nasal discharge
Name 3 possible viral causes of mild respiratory infections in horses
Equine rhinitis virus
Equine adenovirus
Equine herpes virus
Describe the typical haematology results seen in a patient with acute mild viral respiratory disease
- Decreased Neutrophils / lymphocytes
- Then increased Lymphocytes
- ‘reverse differential’
Name the cause of ‘Rattles’
Rhodococcus equi
Horses commonly present with rattles at which age?
3wo - 6mo foals
Describe the disease caused by Rhodococcus equi
Pyogranulomatous pneumonia
How is Rhodococcus equi diagnosed?
Diagnosis by consistent clinical signs and detection of E equi by culture/PCR.
How is Rhodococcus equi treated?
Prolonged antimicrobials - Typically macrolide and rifampin
Strangles is caused by?
Streptococcus equi var equi
Is S.equi part of the normal flora in horses?
No - obligate parasite
Describe the spread of Streptococcus equi var equi
- Survives well in environment, especially in discharges: less in warm / dry conditions
- Spread via nose or mouth contact, fomites.
- Distant spread rare
- Carrier animals harbour organism in guttural pouches
Describe the early clinical signs of strangles
- Depression, fever (2-3 days before shedding bacteria)
- Mucoid nasal discharge
- Slight cough
- Anorexia / difficulty swallowing
- Mild swelling pharyngeal / intermandibular area
What action should you take if a horse presents with depression?
- Monitor horses using daily temperature taking – if this goes up then isolate the horse.
- Hopefully this removes the horse from the healthy population before they start shedding bacteria
Describe the later signs of strangles
- Purulent nasal discharge
- Lymph node enlargement, abscess, and purulent discharge (7-28 days after infection) -> most common: Submandibular / retropharyngeal
- Retropharyngeal LN swelling
- Dyspnoea/dysphagia
- If ruptures -> guttural pouch empyema
What must be considered when looking at the ‘typical’ signs of strangles?
Not all horses will appear with the classical abscess.
They may just have mild respiratory signs.
This depends on factors such as: immunity of the horse, initial infectious dose, strain of the pathogen
Name the condition that develops due to strangles infection
Guttural Pouch Chondroids
Describe the pathophysiology of guttural pouch chondrosis
Chronic guttural pouch empyema -> Chondroids
Removed via breaking up & flushing, or surgery
List the main complications of a strangles infection
- Cellulitis and local tissue damage
- Pneumonia and abscessation
- Immune mediated myositis / myocarditis
- Purpura haemorrhagica
What is Purpura haemorrhagica?
Vasculitis
Type III hypersensitivity
Serum / blood leakage
What is the main complication of bastard strangles?
Metastatic abscesses
How is strangles diagnosed?
PCR (+/- culture) from:
- Nasopharyngeal swabs / lavage
- Guttural pouch washes/aspirates
- Aspirate from abscess
Serology: ELISA for antibodies – tests for exposure only
Characteristic clinical signs
Describe how you can confirm a horse is free from a strangles infection (2 methods)
- Nasal Swabs – 3 negative swabs 1 / week for 3 weeks (85% sure of no infection)
- Guttural Pouch Wash –1 negative to be 88% sure that the horse is free of infection
How is strangles treated?
- Symptomatic pain relief (NSAID’s): to help appetite and reduce swelling
- Soft, wet feed
- Hot pack –helps to mature the abscess
- Flush abscesses once draining
- A tracheostomy is necessary in horses with respiratory distress
Should antibiotics be used in strangles cases?
Antibiotics controversial!
- Do not use ABs when lymphadenopathy present: inhibits maturation of abscess.
- If monitoring in outbreak: At onset of pyrexia, give penicillin for 5-7 days
- No evidence that antibiotics influence development of Bastard Strangles
Should antibiotics be used in strangles cases?
Antibiotics controversial!
- Do not use ABs when lymphadenopathy present: inhibits maturation of abscess.
- If monitoring in outbreak: At onset of pyrexia, give penicillin for 5-7 days
- No evidence that antibiotics influence development of Bastard Strangles
Describe how to manage an outbreak of strangles at a yard
- Shedding can continue for 2-6 weeks after end of nasal discharge (can be longer)
- Biosecurity
- No movement on/off
- Identify ‘carriers’
- Identify persistently infected horses (~10%)
How is strangles prevented?
- Quarantine new animals for 3 weeks
- Use ELISA to detect exposure
- Vaccination: immunity for 3 months
- After recovery from natural infection 75% have long term immunity
What is inflammatory airway disease in horses?
A non-septic inflammation of the lower airways
Inflammatory airway disease is often seen in which horses?
Common in young/new racehorses
List the risk factors for equine inflammatory airway disease
- Co-mingling: just brought in to racing training and exposed to other horses and the environment
- Exercise: strenuous exercise decreases immune function
- Inhalation of dust
- Inhalation of cold, unconditioned air
- Transport
- EIPH
- Age: younger horses most at risk
- Stable environment: esp. poor ventilation and bedding
