Lecture 14 10/23/24

Question 1

What are the characteristics of Rhodococcus equi?

Answer 1

-gram-pos pleomorphic rods
-Chinese character formations
-facultative intracellular pathogen
-soil organism
-harbored in intestinal tract of adult herbivores
-inhaled or ingested
-seen in 1-6 month old foals
-insidious disease (gradual)

Question 2

What are the clinical manifestations of Rhodococcus equi?

Answer 2

-chronic suppurative pneumonia
-anorexia
-lethargy
-fever
-nasal discharge +/- cough
-tachypnea
-dyspnea
-nostril flaring
-abdominal breathing

Question 3

What are the extra-pulmonary manifestations of Rhodococcus equi?

Answer 3

*intestinal manifestations:
-possibly subclinical
-ulcerative colitis
-typhylitis
-suppurative inflammation of colonic/mesenteric lymph nodes
*polysynovitis
*panophthalmitis
*guttural pouch empyema
*sinusitis
*pericarditis
*hepatic and renal abscessation

Question 4

What findings are seen on bloodwork with Rhodococcus equi?

Answer 4

-hyperfibrinogenemia
-neutrophilic leukocytosis +/- monocytosis

Question 5

What findings are seen on radiographs with Rhodococcus equi?

Answer 5

-alveolar pattern
-regional consolidation and/or abscessation

Question 6

Which methods are used to diagnose Rhodococcus equi?

Answer 6

-TTW with cytology and bacterial culture
-PCR

Question 7

What are the characteristics of antibiotic treatment for Rhodococcus equi?

Answer 7

-erythromycin + rifampin
-given for 4-10 weeks
-can use azithromycin or clarithromycin

Question 8

What are the side effects of antibiotic treatment of Rhodococcus equi?

Answer 8

-idiosyncratic hyperthermia and tachypnea
-self limiting fecal softening
-Clostridium difficile enterocolitis in mares exposed to the macrolides

Question 9

What are the supportive treatments for Rhodococcus equi?

Answer 9

-oxygen support
-hyperbaric oxygen
-IV fluids
-nutrition support
-monitoring of fibrinogen
-radiographs/ultrasound for monitoring

Question 10

What is the prognosis of Rhodococcus equi infection?

Answer 10

-treatment is very successful
-poorer prognosis with extra-pulmonary manifestations of disease
-decreased chance of racing as an adult, but performance in those racing not reduced significantly

Question 11

What are the surveillance strategies for Rhodococcus equi?

Answer 11

-daily rectal temps
-fibrinogen levels measured every 2 weeks
-WBC count measured every 2 weeks
-ultrasound every 2 weeks (detects peripheral lesions only)

Question 12

How is Rhodococcus equi controlled?

Answer 12

-avoid high animal density
-avoid sandy/dusty soils and manure laden areas
-pasture rotation
-plant or irrigate dusty paddocks/pastures
-surveillance strategies
-hyperimmune plasma
-prophylactic administration of azithromycin

Question 13

What are the terms used for moderate/severe and mild equine asthma?

Answer 13

moderate/severe: recurrent airway obstruction/RAO
mild: inflammatory airway disease/IAD

Question 14

What are the characteristics of equine asthma?

Answer 14

-naturally occurring
-periods of reversible airway inflammation

Question 15

What causes the clinical signs of equine asthma?

Answer 15

-neutrophil accumulation
-mucus production
-bronchospasm

Question 16

What is the impact of equine asthma on the lungs?

Answer 16

-decreased compliance
-increased resistance
-increased work of breathing
-arterial hypoxia

Question 17

What is the epidemiology of equine asthma?

Answer 17

-seen in horses that are stalled and fed hay
-increased incidence with age
-familial tendency

Question 18

What is the pathophysiology of equine asthma?

Answer 18

-inhalation of dusts and molds increases IL-8 production
-neutrophil accumulation leads to small airway obstruction
-mucus accumulation, bronchospasm, and inflammatory changes in airway walls increase small airway obstruction
-obstruction leads to V/Q mismatch (poor vent., normal perfusion)
-inefficient gas exchange leads to hypoxia
-horses increase resp rate to compensate, but tidal vol. remains the same
-abnormal breathing pattern occurs

Question 19

What is the typical history of a horse with equine asthma?

Answer 19

-stalled and eating hay
-coughing
-decreased exercise tolerance
-prolonged recovery from exercise
-nasal discharge
-resp distress

Question 20

What are the clinical signs of equine asthma?

Answer 20

-cough
-nasal discharge
-flared nostrils
-increased resp rate
-rapid inspiration and forced prolonged expiration
-weight loss
-increased effort of breathing
-heave line

Question 21

What can be heard during auscultation in horses with asthma?

Answer 21

-can be quiet
-increased breath sounds
-crackles and wheezes
-tracheal rattle

Question 22

What findings can be found on arterial blood gas in horses with asthma?

Answer 22

-chronic respiratory acidosis
-hypoxemia
*depends on magnitude of resp compromise

Question 23

What is the primary finding on BAL in equine asthma?

Answer 23

non-degenerate neutrophilic inflammation

Question 24

What are the findings on radiographs in equine asthma?

Answer 24

-increased bronchovascular and interstitial changes
-lung hyperinflation

Question 25

What is an atropine or buscopan test?

Answer 25

short lived broncho-dilator administration to determine if patient symptoms improve *associated with development of ileus

Question 26

What are the options for allergy testing in horses?

Answer 26

-serum -intradermal

Question 27

What are principles of equine asthma control?

Answer 27

-environmental control -reduce inflammation -relieve resp distress

Question 28

Which components of environmental control are important for equine asthma?

Answer 28

-house horses 100% outdoors -bedding -diet

Question 29

How can inflammation be reduced in equine asthma?

Answer 29

-NSAIDs -inhaled or systemic corticosteroids

Question 30

Which systemic corticosteroids are used in equine asthma?

Answer 30

-dexamethasone: short acting and easily withdrawn -prednisolone: less side effects -triamcinolone: long acting

Question 31

What are the characteristics of systemic corticosteroids for equine asthma?

Answer 31

-oral or injectable -more side effects since acting systemically -lowest possible dose is used -help to prevent airway remodeling

Question 32

Which inhaled corticosteroids are used in equine asthma?

Answer 32

-beclomethasone -fluticasone

Question 33

What are the characteristics of inhaled corticosteroids for equine asthma?

Answer 33

-use metered dose inhalers -not systemic, less side effects -not for initial or emergency use; require animal to take deep breaths

Question 34

Which classes of bronchodilators are used to relieve resp distress?

Answer 34

-anticholinergics -beta-2 adrenergic agonists -methylxanthines

Question 35

What are the characteristics of atropine?

Answer 35

-anticholinergic -IV -ileus and excitement with repeat doses

Question 36

What are the characteristics of ipratropium?

Answer 36

-anticholinergic -inhalation -no side effects

Question 37

What are the characteristics of clenbuterol?

Answer 37

-beta-2 agonist -given oral or IV -only FDA approved bronchodilator for horses

Question 38

What are the characteristics of albuterol?

Answer 38

-beta-2 agonist -given oral or IV -not well absorbed orally in horses

Question 39

What are the characteristics of theophylline?

Answer 39

-methylxanthine -oral -erratic absorption and narrow therapeutic index

Question 40

What are other potential treatments for equine asthma?

Answer 40

-mucolytic drugs -antihistamines

Question 41

What are the steps to prevention of equine asthma?

Answer 41

-provide clean, well ventilated housing -properly treat and manage resp disease

Question 42

What is the prognosis of equine asthma?

Answer 42

-dependent on disease stage -unknown if chronic airway remodeling can be reversed -important to prevent recurrence of airway inflammation -expensive to maintain lung health