Equine Respiratory Disease Flashcards
What is the pathogenesis of equine Strangles? What are common clinical signs?
Streptococcus equi subsp. equi shed in respiratory secretions of infected horses are inhaled or ingested
- fever, lethargy, anorexia
- mucopurulent nasal discharge originating from guttural pouch empyema
- enlarged head and neck LNs, most commonly submandibular –> can progress to abscessation
What are 3 sequela of equine Strangles?
- bastard strangles - dissemination of abscesses to internal organs
- purpura hemorrhagica - aseptic vasculitis (severe edema, petechiae, septicemia) due to an immune reaction from repeated exposures to natural infection or vaccination
- chondroids - solidified caseous material in guttural pouches, can persist for years and be a source of bacterial shed
How are acute and chronic cases of equine Strangles diagnosed?
ACUTE - PCR from nasal swab, nasopharyngeal lavage fluid, or guttural pouch lavage fluid + bacterial culture
CHRONIC - serology for SeM-specific antibody –> high titers suggest purpura hemorrhagica or bastard strangles + guttural pouch endoscopy
What treatments can be used for equine strangles? What is most commonly done? What is contraindicated?
- lavaging guttural pouch and instilling Penicillin to speed clearance
- anti-inflammatories
- supportive care
- emergency tracheostomy if LN abscesses become large enough to block off the airway
natural clearance of infection
systemic antibiotics - can prolong clearance and recovery, only used in complicated or severe cases
When will a horse no longer be considered a carrier for equine Strangles?
negative guttural pouch fluid PCR or 3 negative nasal PCRs
How can equine Strangles be prevented?
- isolate new or infected horses with strict biosecurity
- modified-live IN vaccine or killed IM vaccine
What method of prevention of equine Strangles is contraindicated in outbreaks?
vaccination –> increases risk of purpura hemorrhagica
What is the major risk factor for horses becoming infected with equine herpesvirus 1 and 4 (equine rhinopneumonitis)? What is the pathogenesis?
young horses that show or travel with frequent exposure to other horses
- EHV1 and 4 are endemic in the equine population and remain latent in individuals until times of stress
- then it can cause clinical or subclinical disease and allow for spread via respiratory secretions
What is a possible sequelae to equine herpesvirus 1 infection?
mutation into an EHV-1 wildtype or neurogenic strain to cause equine herpes myeloencephalopathy (EHM)
What are some possible clinical signs associated with equine herpesvirus 1 infection?
- fever, lethargy, anorexia
- cough
- mucopurulent nasal discharge
- secondary pneumonia
- abortion in pregnant mares - EHV1 can rarely infect the endometrium and fetal tissues
(worse in naive young horses <5 y/o, vaccinated horses will have less severe signs and can act as a source of subclinical spread)
How is equine herpesvirus 1/4 infection diagnosed? Treated?
PCR of nasal discharge
- anti-inflammatories
- supportive care
- antiviral drugs
- antibiotics for secondary pneumonia
How can equine herpesvirus 1/4 infection be prevented?
- isolate new horses or infected horses with strict biosecurity
- MLV IN or killed IM vaccine - biannual in high-risk horses and mares during pregnancy to prevent abortion
What is a major risk factor for horses to become infected with equine influenza A? What is the pathogenesis?
endemic in the equine population - outbreaks commonly from horses that show or travel with frequent exposure to other horses, especially young horses and racehorses
inhalation of aerosolized virus from respiratory secretions
What clinical signs are associated with equine influenza A infection?
- fever, lethargy, anorexia
- dry cough
- mucoid nasal discharge
- secondary pneumonia
How is equine influenza A infection diagnosed? Treated?
PCR of nasal discharge
- anti-inflammatories
- supportive care
- antibiotics for secondary pneumonia
How can equine influenza A infection be prevented?
- isolate new horses or infected horses with strict biosecurity
- MLV IN or killed IM vaccine - biannual in high-risk horses
In what horses is exercise-induced pulmonary hemorrhage (EIPH) most prevalent? What can increase risk?
athletic horses in high-speed events - racehorses, barrel racers
previous lung damage or chronic infections
What is thought to be the pathogenesis of EIPH in horses? What are the most common clinical signs?
high capillary pressure from high cardiac output causes wall failure and hemorrhage into airspace
- epistaxis during or immediately after an athletic event
- swallowing repeatedly after an event
- poor performance, slow to recover
What are 2 options for diagnosing EIPH in horses?
- airway endoscopy to identify hemorrhage (most diagnostic within 2 hours of event)
- cytology of airway via BAL within a few days of event to identify RBCs and hemosiderophages
What 2 treatments are used for EIPH in horses? What is prognosis like?
- Furosemide - decreases interstitial pressure and reduces hemorrhage
- antibiotics - prevent secondary risk of pneumonia
excellent for survival, repeated bleeding episodes in future events
What are 4 risk factors for horses to develop recurrent airway obstruction (RAO) or heaves? What is the pathogenesis?
- warm, dry climates
- horse kept inside with less turnout
- barns with poor ventilation
- dusty or dirty environments
inflammation of the lower airways cause bronchospasm, excess mucus, and airway remodeling = partially obstructed airways
What clinical signs are associated with RAO (heaves) in horses? What is seen in chronically affected horses?
- tachypnea, dyspnea
- respiratory noise with flared nostrils
- dry coughing
- wheezing noise during respiration, especially during end exhalation
- affected horses are afebrile, BAR, and may be asymptomatic between flare-ups
heave line - hypertrophied external abdominal oblique from chronic muscle effort to exhale
How is RAO (heaves) diagnosed?
cytology of BAL = increased neutrophils
What is critical for treatment of RAO (heaves)? What 4 medications are used?
environmental modifications - reduce dust in bedding and feed, turn out in pasture, stabled with good ventilation
- corticosteroids - inhaled or systemic
- bronchodilators - Albuterol, Vnetipulmin inhaled or oral
- oral antihistamines - unknown effectiveness
- allergen testing and desensitization
What is the prognosis of horses with RAO (heaves)?
management and treatment of decrease to control disease flares, but it’s a chronic disease that is rarely cured
What is the most common cause of sinusitis in horses? What clinical signs are associated?
secondary to a dental problem - usually 08-11 with 09 most common
- chronic, unilateral, mucopurulent, and foul smelling nasal discharge (commonly resolves with antibiotics, but recurs when discontinued)
- afebrile, BAR
What is the best diagnostic for sinusitis in horses? What are other options?
head and dental radiography or CT, especially to identify dental involvement
- culture and/or PCR of discharge to r/o other viral or bacterial causes
- nasal endoscopy to identify neoplasia, masses, etc.
What are 3 important parts to the treatment of sinusitis in horses? What is prognosis like?
- extract affected teeth
- repeated sinus lavage for up to a week, can use a bone flap to allow better lavage
- culture with appropriate antibiotics
good - treatment may be intensive
In what horses is laryngeal hemiparesis (roaring) prevalent? What is the pathogenesis?
Thoroughbreds, Warmbloods, and other large breed athletic horses
idiopathic neuropathy of the left recurrent laryngeal nerve causes the left arytenoid cartilage to partially or completely fail to abduct during inspiration, resulting in an airway obstruction
- left recurrent laryngeal nerve is the longest one
What clinical signs are associated with laryngeal hemiparesis (roaring) in horses?
- upper respiratory noise at inspiration during exercise
- exercise intolerance
- poor performance
How is laryngeal hemiparesis (roaring) in horses diagnosed? Treated?
upper airway endoscopy when the horse is exercised and un-sedated
laryngoplasty (tie-back) with or without cordectomy - ties open the left arytenoid, which causes an increased risk of cough or (aspiration) pneumonia if not well-placed
What is the pathogenesis of Rhodococcus equi infection? What horses are most commonly infected?
organism lives in the soil and can survive for years, so horses on farms or larger breeding operations can have constant inhalation and endemic disease
foals/weanlings 1-3 months olf
What clinical signs are indicative with Rhodococcus equi infection? What is seen on labwork?
foal/weanling (1-3 m/o) with pyogranulomatous bronchopneumonia:
- fever
- tachypnea
- lethargy, anorexia, poor weight gain
- more rarely: cough, nasal d/c
- dissemination: septic arthritis, uveitis, internal abscesses, immune-mediated disease, GI involvement, etc.
hyperfibrinoginemia
What are 2 ways of diagnosing Rhodococcus equi infection?
- transtracheal wash cytology = intracellular rods (+ culture!)
- abscesses on lungs seen with thoracic U/S or radiography
What treatment is required for Rhodococcus equi infection?
4-10 week antibiotic treatment with rifampin + azithromycin or erythromycin
How can Rhodococcus equi infection be prevented?
farms with endemic disease can treat all foals with R. equi hyperimmune plasma at birth and at 1 month
What are 3 risk factors that contribute to the development of pleuropneumonia (Shipping Fever) in horses?
- recent transport, especially of extended duration (>6 hr) with poor ventilation and infrequent rest stops
- tying horses’ heads high, which decreases ability to clear airways
- other infections: respiratory disease, dysphagia, esophageal obstruction, etc.
What is the pathogenesis of pleuropneumonia (Shipping Fever) in horses?
bacterial pathogen in lung parenchyma extends to pleural space and cause pleural effusion
When do clinical signs of pleuropneumonia (Shipping Fever) appear in horses? What is seen?
within 24 hours of travel
- severe fevers (>104 F)
- lethargy, anorexia, depression
- dyspnea, tachypnea
- decreased lung sounds ventrally
- nasal d/c, mild cough
- reluctance to move due to pleural pain from accumulating fluid
How is pleuropneumonia (Shipping Fever) in horses diagnosed? Treated?
thoracic U/S
- systemic support: IV fluids, anti-inflammatories, antibiotics, supplemental oxygen
- thoracocentesis and indwelling chest tubes
How does gastroesophageal obstruction (choke) commonly mimic respiratory disease in horses? What can happen if treatment is delayed?
can present with nasal discharge or coughing
aspiration pneumonia –> needs to be resolved within 6-12 hours
What are 3 risk factors that contribute to horse developing choke?
- older horses with poor dentition
- horses that eat rapidly, especially in a herd environment
- horses fed large quantities of dry grain or pellets
What is the pathogenesis of gastroesophageal (choke) in horses?
food bolus is not properly chewed into small enough particles and becomes lodged in the esophagus, causing more feed and saliva to back up
What clinical signs are indicative of choke in horses?
- copious bilateral nasal d/c, usually initially green tinged, but as it continues, it becomes saliva only and interpreted as respiratory nasal d/c
- coughing, gagging, retching, ptyalism
- colic
- anxiety
How is choke diagnosed? Treated?
inability to pass a nasogastric tube
- gentle lavage with water via nasogastric tube
- sedate to lower head and reduce the risk of aspiration
- esophageal muscle relaxants, like oxytocin or bucospan
- antibiotics, anti-inflammatories
What treatment is contraindicated when treating choke?
lubricants –> risk of aspiration pneumonia
