Module 4 (Week 7-8) Flashcards by Kianelys Heredia

Module 4A: Equine Viral Respiratory Disease

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A very common DNA viruses in horse populations worldwide

Equine herpesviruses (EHV)

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Is a common, highly contagious equid respiratory disease

Equine influenza virus (EIV)

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Other EHV’s – EHV-2 and -5 (the y-herpesviruses)
- Upper respiratory infection
- Abortion
- Vasculitis

Equine Viral Arteritis (EVA)

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Other EHV’s – EHV-2 and -5 (the y-herpesviruses)
- Mild URI
- Poorly characterized currently

Rhinoviruses - ERAV and ERBV’s (n=3)
Remember: equine ‘rhino’ is not the same as rhinovirus (that horseman’s terminology again…)

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In the setting of respiratory disease, list the alpha- herpesviruses:

EHV -1 – URT
EHV -4 – URT

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In the setting of respiratory disease:
- Is ubiquitous and of questionable pathogenicity
- Localized to respiratory mucosa, conjunctiva, WBC’s

EHV -2 (cytomegalovirus)

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In the setting of respiratory disease:
- May be involved in syndrome of pulmonary fibrosis (EMPF = equine multinodular pulmonary fibrosis)

EHV -2 and -5

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EHV -1 and EHV -4 are _______ genetically similar

70%

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Differences between EHV -1 & EHV -4:
- Upper respiratory disease
- Abortion
- Birth of severely compromised foals
- Neurologic disease

EHV -1

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Differences between EHV -1 & EHV -4:
- Primarily mild upper respiratory disease

EHV -4
- VERY common infection in young horses
- Viral infection limited to respiratory tract epithelium, regional lymph nodes

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Can be very similar clinically to influenza
Requires additional ancillary diagnostic tests to differentiate
However, usually mild (sometimes clinically inapparent)
More common in weanling foals (2-6 months old)
- Aerosol spread
- The dam is usually the source

Respiratory disease (EHV -1 & -4)
- ‘Rhinopneumonitis’
- Clinical Signs:
- Incubation: 2-10 days
- Fever
- Serous nasal discharge
- Cough
- Inappetance
- Submandibular lymphadenopathy, lymphoid hyperplasia (pharyngeal)
- Secondary bacterial infections can occur
- Tracheobronchitis
- Bronchopneumonia

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List the main two things for respiratory disease associated with EHV -1 & -4:

Most common in YOUNG horses
Usually MILD

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(T/F) There is a vaccine for EHV -1 Myeloencephalopathy

False

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List the methods you can use to diagnose EHV -1:

Virus isolation
PCR –> NASAL SWAB & WHOLE BLOOD
Fluorescent antibody
Serology

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What are the treatments for EHV -1, -4?

Supportive Care
- Anything more than this is probably unnecessary and, if required, should suggest that something ELSE is going on

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(T/F) EHV -1 vaccination protects against neurologic disease

False, does NOT protect against neurologic disease
- We don’t know the best way(s) to vaccinate horses against EHV -1/4 to protect against EHM

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Orthomyxovirus
Type A (antigenic drift and shift COMMON)
Single-stranded, negative-sense, segmented RNA virus
Two subtypes in horses: H3N8 and H7N7
- H7N7 not documented in outbreaks for >20 years
- Two lineages of H3N8
- Eurasian/European
- American
Worldwide, the most common viral respiratory infection in horses

Equine Influenza

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Transmission - inhalation of virus
Highly contagious
Particularly prevalent in young horses
- Generally not in horses less than 1 year of age
- Risk factors (mixing, shipping, training, etc.)
Major concern in areas of high population density
Often develop secondary bacterial infection
- Effects on ciliated respiratory tract epithelium

Equine Influenza
- Horses can expel the virus during coughing with enough velocity to infect other horses up to 35 yards away

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What does equine flu look like?
- Incubation period: _________
- Clinical Signs: ______
- Ventral, limb edema may occur
- Purpura hemorrhagica reported post-infection
- Secondary bacterial infections COMMON!!

about 1-3 days (SHORT)
Dry, hacking cough

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Diagnosis for Equine Flu?

PCR
Nasal Swab
Clinical signs and evidence of high level of contagion = suggestive

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Module 4B: Equine Bacterial Respiratory Disease

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List risk Factors for Pleuropneumonia (‘Equine shipping fever’):

Transportation (distance)
Head tied up during transport
Insufficient time with head lowered during breaks
Altered mucociliary clearance (viral disease)
Altered pulmonary macrophage function
Stress; immunosuppression
Racehorses
Esophageal obstruction
Poor definition
General anesthesia

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Fever
Tachypnea
Purulent/hemorrhagic nasal discharge
Lethargy
Inappetance
Injected, ‘toxic’ mucous membranes
- Toxic line
Weight loss
These are the clinical Signs:

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Pleuropneumonia

What can be an immediate diagnostic of pleuropneumonia?

Ultrasonography

List Pleuropneumonia treatment:

- Thoracic drainage, lavage - Broad-spectrum antibiotic coverage - Fluid therapy - Anti-inflammatories - *Laminitis prophylaxis*-> stand them in ice - Nutritional therapy - Respiratory support - Thrombolytics

What is the prognosis for survival of Pleuropneumonia?

- Fair to good, if survive acutely - Recovery = prolonged (months) - Treatment is expensive - Prognosis for *performance* is *guarded* - See complications - Adhesions are problematic

Definition: the formation of fibrotic bands that span the pleural space, between the parietal and visceral layers of the pleura

Pleural adhesions

- *Gram (+) chaining cocci* - Long Chains - (Short Chains = S. equi subsp. zooepidemicus) - Very contagious - Infection, disease limited to equids - Bimodal age distribution - Youngsters (weanling -- 2 years of age) - Middle-aged to older horses - Asymptomatic Carriers

Streptococcus equi subsp.equi - Equine 'Strangles'

Why Strangles could be eradicated?

- Only equids - Fever occurs about *48* hours prior to nasal shedding of the organism - Not terribly persistent in the enviroment

Strangles: In a small proportion of recovered horses, a *carrier state* is established. This requires diagnostic testing of the ________ to confirm

guttural pouches

- Immune-mediated vasculitis - Type III hypersensitivity (Arthus reaction) - Clinical Signs: - A few days to several weeks post-recovery from *strangles* - *Fever*, lethargy, malaise - Distal limb, ventral edema; can progress to skin sloughing - *Petechiation* of mucous membranes - Diagnosis - Most are treated presumptively - Serum M-protein titer - Skin biopsy -- Leukocytoclastic vasculitis

Purpura Hemorrhagica

What are the Vaccinations for 'Strangles'?

- Inactivated M-protein derivative vaccine - Modified live intranasal vaccine

- Gram (+) - Pleomorphic coccobacillus - *Soil saprophyte* - Facultative intracellular pathogen - Can survive and replicate within macrophages - *VapA*

Rhodococcus equi - Immunocompromised - human problem too

(T/F) Foals are infected EARLY with R. equi (Likely within the first 7-10 days of life)

True

R. equi: Clinical Disease Syndrome in Horses - Weanling foals (2-6 months of age)

*Pyogranulomatous bronchopnemonia*

Clinical Signs: - Mild to severe - Most common -- *Fever* - Cough, nasal discharge -- *unreliable* signs of respiratory disease in foals

R. equi Bronchopneumonia

Which of the following best describes how a weanling filly with uncomplicated strangles should be treated?

Supportive care (NSAIDs, soft feed, careful monitoring of respiratory rate and effort) and isolation/biosecurity

You are presented with a 2-year-old American Quarter Horse colt that returned home from a large national show 10 days ago and now has a fever, bilateral mucopurulent nasal discharge, and greatly enlarged submandibular lymph nodes. Which disease do you suspect, and what test would you ideally use to confirm your suspicion?

Strangles (Streptococcus equi subsp. equi infection); culture and PCR of guttural pouch lavage fluid

Which of the following is a known risk factor for equine shipping fever (septic bronchopneumonia/ pleuropneumonia)?

Prolonged transport, particularly with infrequent stops and the head tied

Regarding Rhodococcus equi infections in equids, which of the following statements is FALSE?

The disease is rarely documented outside of the respiratory tract

You are presented with a 4 month old Thoroughbred colt for evaluation of bilateral mucoid nasal discharge of 5 days’ duration. The colt’s physical examination is otherwise normal; which of the following is an unlikely differential diagnosis for this patient?

Septic pleuropneumonia

You are presented with a 3-year-old Standardbred filly with significant dependent edema, fever, and inappetence that have all developed acutely in the last 24-36 hours. She is housed on a farm on which strangles is endemic, and she recently recovered from the disease ~3 weeks ago. What condition do you now suspect, and how should this complication best be treated?

Purpura hemorrhagica; penicillin and dexamethasone

Module 4C: Equine Non-Infectious Respiratory Disease

Definition: Is a highly prevalent respiratory disease affecting *adult horses*

Severe equine Asthma - Recurrent airway obstruction (RAO), 'Heaves' - *Common* non-infectious lower airway disease - Reactive, *inflammatory* airway disease

List the 3 hallmark characteristics of RAO:

1. Airway inflammation -- neutrophil accumulation 2. Bronchoconstriction, increased airway reactivity 3. Mucus production

List the Clinical Signs for RAO:

- *Most common = cough (80%) - esp. in first few minutes of work and when fed* - Expiratory effort - Nostril flaring at rest - Nasal discharge - Exercise intolerance *Episodic and progressive*

What are the main diagnoses of Severe Equine asthma?

- History - Auscultation - Bronchoalveolar lavage fluid cytology

BALF cytology: ________% BALF non-degenerate neutrophils = considered diagnostic

>20

(T/F) Many of the cases of equine asthma are controlled with management changes alone

True, never forget management, this should come first

(T/F) EIPH has been reported in horses that complete in *all* of equine sport disciplines

True

Definition: Is bleeding that occurs from the lungs of horses during exercise

Exercise‐induced pulmonary hemorrhage (EIPH)

You are presented with a 16 year old Tennessee Walking Horse mare for evaluation of intermittent productive cough of 3-4 months’ duration. The condition appears to wax and wane, with cough most frequently noted when the mare eats and when she is ridden. She otherwise appears well; no treatment has been attempted to date. You are highly suspicious of one disease in particular; which of the following therapeutic strategies would you initiate FIRST for this disease (assuming that diagnostic test results are supportive of this diagnosis)?

Move the mare from her dusty stall to a grass paddock (permanently)

What are the three hallmark pathologic changes that characteristically occur in the small airways of horses with severe equine asthma (formerly known as recurrent airway obstruction/RAO, or ‘heaves’)?

Inflammation, bronchoconstriction, and mucus production

Regarding equine exercise-induced pulmonary hemorrhage (EIPH), which of the following statements is TRUE? - Administration of furosemide prior to a race has been shown to attenuate EIPH and provide a performance benefit to horses that receive it. - No treatments that have been attempted for this condition (and there have been MANY) have been shown to be effective in controlled studies. - Affected horses tend to be younger and slower than unaffected horses. - EIPH only occurs in Thoroughbred racehorses.

Administration of furosemide prior to a race has been shown to attenuate EIPH and provide a performance benefit to horses that receive it.

Which of the following is the MOST sensitive diagnostic test for equine EIPH (i.e., ~90% of Thoroughbred racehorses are bleeders if evaluated with this modality)? - Cytologic evaluation of bronchoalveolar lavage fluid - Thoracic radiography - Visual inspection of the nares - Tracheal brush cytology

Cytologic evaluation of bronchoalveolar lavage fluid

A rebreathing examination is a technique that involves thoracic auscultation after encouraging the horse to take a few deep breaths by (carefully) placing a plastic bag over its nose for a minute or two (during which time it will ‘rebreathe’ exhaled CO2, slightly increasing the paO2, and increasing the rate and depth of respiration briefly when the bag is removed). This technique increases the sensitivity of auscultation for detection of certain respiratory sounds, particularly expiratory wheezes; it is therefore most likely to be useful in the evaluation of a patient with which of the following diseases?

Severe equine asthma

What percentage of neutrophils in bronchoalveolar lavage fluid would support a diagnosis of severe equine asthma/’heaves’?

>20%

Module 4D: Equine Respiratory Cases

Module 4 (Week 7-8) Flashcards

(59 cards)