Lecture 20: Equine Respiratory Diseases (MacKay) Flashcards
Dx/Txof guttural pouch mycosis
Dx: endoscopy, culture (Emericella, Aspergillus, etc.)
Tx: sx occlusion of affected artery or systemic and/or topical antifungal if less severe
guttural pouch tympany
distension of one or both guttural pouches with air. Occurs in horses <1yo
CS/Dx/Tx of guttural pouch tympany
-external swelling in parotid area
-dyspnea if severe
-rarely dysphagia
Dx based on CS
Tx: surgical
Primary sinusitis and Tx
-maxillary sinus most commonly affected
-S. equi zooepidemicus commonly involved
Tx: systemic Abx, sinus flush
2ary sinusitis and Tx
causes tooth root abscess
Tx: systemic abx, tooth extraction, tooth repulsion through maxillary sinus flap
CS of sinusitis
- unilateral nasal discharge**
- ozena
- ocular discharge
- facial sensitivity/deformity
Dx of sinusitis
- percussion
- rads
- endoscopy
- oral exam
- CT
2 main viral resp. diseases
influenza herpes virus (rhinopneumonitis)
Viral resp. diseases general CS
fever, cough, nasal d/c
Dx of viral resp. diseases
- virus isolation
- PCR amplification***
- Serology (paired samples 10-14 days apart)
- Ag detection
most common cause of severe epidemics of upper respiratory disease in horses**
Equine Influenza. Comprises 40-60% of cases
What type of virus is equine influenza?
orthomyxovirus with an RNA genome
-only influenza type A to affect horses
How is level of virulence determined in equine influenza?
By some combination of Hemagglutinin (HA) and Neuaminidase (NA) immunodominant antigens which are used to penetrate the cells
What combos of HA and NA have been id’d in horses?
H7N7
H3N8 <—major subtype***
What is unique about H3N8 strain of equine flu?
subject to antigenic drift, in which HA or NA mutate so that virus can escape neutralization by antibody made to earlier strains. It likes to accumulate mutations over time
incubation period of equine flu
1-3 days
equine flu affects which pop. of horses the most?
1-3 year old horses in training
pathogenesis of equine flu
1) aerosol infection
2) adhesion to resp. ep.
3) desquamation of ciliated cells
4) decreased mucociliary clearance
morbidity/mortality of equine flu?
high morbidity (100%), low mortality
CS of equine flu
- acute onset fever
- anorexia, depression
- dry cough
- serous nasal discharge
- submandibular lymph node enlargement
Dxof equine flu
- viral isolation (difficult)
- RT-PCR***
- serology (retrospective only)
- influenza A Ag detection Kit: rapid
Possible complications of equine flu
- bacterial pneumonia/pleuropneumonia
- myositis
- myocarditis
how long does it take tracheal ep. to restore after equine flu?
1 month, but horses appear healthy after 1 week
Tx of equine flu
3 wks rest
NSAIDs for fever
Abx for 2ary bacteria pneumonia
Antiviral usually NOT warranted
How long does immunity last following natural equine flu infection?
1 yr
Types of vax for equine flu
1) killed IM
- effective for 3-4 mo
- provides transient systemic IgG response
- not effective in presence of maternally-derived Ab
- does not prevent infection/shedding
2) MLV IN
- protect 6-12mo
- does not provide systemic response
3) Canary Pox Vector Vax
- use in foals of vaccinated dams
- provides robust immune response
Effects of Equine Herpesvirus-1 (EHV-1)***
- abortion
- perinatal dz and death
- neuro
- resp. dz
- viremia (virus in blood) is common**
EHV-2 effects
- mild resp. signs
- immunosuppression?
- keratoconjunctivitis
EHV-3 effects
equine coital exanthema (genital horsepox)
EHV-4 effects***
respiratory disease (rhinopneumonitis)
EHV-5 effects
Equine Multinodular Pulmonary Fibrosis (eventually fatal)
What percent of horses carry EHV-1 or 4 in a latent state?***
85% (in lymph nodes, trigeminal ganglia)
path. of EHV-1 and 4
- young horses
- responsible for 15-20% of outbreaks of URT dz!
- up to 85% of horses are carriers!!**
- acquired via inhalation or recrudescence of a latent infection
- incubation period 2-10 days
- viremia common in EHV-1 infections
Dx of EHV-1 and 4
- virus isolation or PCR amplification <–**
- serology (not important)
vax. for EHV-1 and 4
inactivated or modified live vaccines available for EHV-1, 4, or both
-labeled to prevent abortion
foal pneumonia***
- leading cause of morbidity and mortality!!
- inhalation of aerosolized or dust-borne pathogens
- causes bacteremia and hematogenous spread of bacteria to the lungs in neonates (1-10 mo.)
CS of foal pneumonia
- cough
- bilateral nasal d/c
- fever
- inc. resp. rate
- resp. distress
Dx of foal pneumonia
- abnormal lung sounds
- hematology: neutrophilic leukocytosis, hyperfibrinogenemia
- rads and ultrasonography
- tracheobronchial aspiration: mainly degenerate neutrophils +/- bacteriaon cytology
most common cause of foal pneumonia***
streptococcus equi subs. zooepidemicus
agents of foal pneumonia
strep equi zooepidemicus***
Rhodococcus equi
others: Pasteurella, E. coli, Klebsiella, Actinobacillus,etc.
tx of foal pneumonia
Abx: -Ceftiofur (broad spec) -Penicillin (for S. zooepidemicus) -Trimethoprim-sulfa (oral, mostly useless now) -Penicillin-aminoglycoside O2 therapy
Duration of therapy for foal pneumonia based on:
-resolution of CS
-normal WBC count and fibrinogen concentrations
-imaging techniques (rads, ultrasound)
Only stop tx when everything is normal!
prognosis of foal pneumonia
usually complete recovery if dx/tx early
rhodococcus equi pneumonia path.
- Gram + facultative intracellular pathogen (NOT obligate!)
- can survive and replicate in macs
- normal inhabitant of soil
- infection by inhalation
- can be devastating dz
- usually affects foals 1-6 mo.
CS of rhodococcus equi pneumonia
-bronchopneumonia Extra-pulmonary disorders: -intestinal manifestations --> weight loss -non septic immune-mediated polysynovitis -septic arthritis and osteomyelitis -uveitis -ulcerative lymphangitis, cellulitis -abscesses
Dx of rhodococcus equi pneumonia
- hematology: neutrophilic leukocytosis, hyperfibrinogenemia
- rads/ultrasound
- tracheobronchial aspiration: degenerate neuts, Gram + coccobacillus on gram stain, culture, PCR***
only way to make definitive dx of rhodococcus***
tracheobronchial aspiration
Tx of rhodococcus equi pneumonia
long-term therapy of macrolide and rifampin abx (able to penetrate caseous material and cells)
side effect of macrolides
suppress sweating –> hyperthermia
prog. of rhodococcus equi pneumonia
survival rates b/w 60-80%
affected foals less likely to race, but perform as well
prevention of rhodococcus pneumonia
- decrease size of infective challenge (i.e. prevent grass degradation)
- earlier recognition/close monitoring
- hyperimmmune plasma
pneumonia
infection involving the lung parenchyma
pleuropneumonia
pneumonia or lung abscess that extends to and involves the visceral pleura
most common cause of pleuropneumonia
bacteria
causes of pleural effusion
- pneumonia
- pleuropneumonia
- hemothorax
- chest wound
- neoplasia
- hypoproteinemia
- CHF
Path. of pneumonia/pleuropneumonia
viral infection/toxic gases/stress/malnutrition/general anesthesia –> decreased # and bactericidal activity of alveolar macs –> pneumonia/pleuropneumonia
CS of pneumonia/pleuro.
- fever*
- anorexia, depression*
- tachypnea, resp. distress
- soft cautious cough
- pain in thorax
- bilateral nasal d/c
- fetid breath
- ventral edema
- colic-like signs
- weight loss if chronic
- won’t lay in lat. recumb.
infectious agents of pneumonia/pleuro.
- S. equi zooepidemicus
- Gram - bacteria (Pastuerella, E. coli, Klebsiella, Pseudomonas, Enterobacter)
- Anaerobes (Bacteroides, Peptostrep., Eubacterium)
Dx of Pneumonia/Pleuro.**
- auscultation: decreased lung sounds ventrally and presence of pain
- percussion: horizontal line
- pleurodynia (pleural pain)
- hematology: leukopenia followed by leukocytosis, hyperfibrinogenemia
- ultrasonography, rads
- tracheobronchial aspiration***
- cytology: degenerate neuts +/- bact.
- culture: more likely to yield + culture than pleural fluid
- thoracocentesis
Tx of pnuemonia/pleuro:
1) Abx
- initially broad-spec, then based on culture/sensitivity
- long-term usually required
2) Pleural drainage
- removal of exudate
- re-expansion of lungs
* Go all out on Day 1!!*
3) Supportive care
- fluids
- prevention of endotoxemia
- analgesia
4) thoracotomy and rib resection
- chronic cases
- manual removal
Complications of pneumonia/pleuro.
- endotoxemia
- thrombophlebitis (vein swelling)
- laminitis
- pleural and/or pulmonary abscess form.
- pneumothorax
- pericarditis (rare)
Prog. of pneum/pleuro.
38-75% survival depending on how quickly tx is started
40-60% of survivors race
Exercise-Induced Pulmonary Hemorrhage (EIPH)
presence of blood in the airways after intense exercise/pulmonary hemorrhage (usually caudodorsal lung fields)
Incidence of EIPH
5% of race horses have epistaxis
Up to 90% of race horses have EIPH!
EIPH effect on performance**
unlikely; rule out all other causes!
Dx of EIPH
- endoscopy
- cytology (TBA or BAL): hemosiderin-laden macs
- rads: opacities in caudodorsal lung fields
path. of EIPH
failure of pulmonary capillaries during exercise when pressure exceeds 70 mmHg
Tx of EIPH
furosemide (loop diuretic)
-decreases pulmonary capillary pressure
nasal strips
Heaves aka
RAO (recurrent airway obstruction)
COPD
heaves affects young/mature horses?
mature >3 yo
Path. of Heaves
fungi/molds/endotoxins/allergens –> hypersensitivity/non-specific inflammation –> bronchiolitis, neutrophilic airway infiltration, excess mucus, bronchoconstriction
genetic disposition also possible
Path.of hypersensitivity reactions in Heaves
1) Type I –> IgE, mast cell degranulation
2) Type III –> IgG or IgM, immune complexes
CS of mild heaves
intermittent cough
exercise intolerance
abnormal lung sounds
mild increase in resp. rate
CS of severe heaves
resp. distress
abd effort during expiration (heavy line)
weight loss
When is fever present in Heaves?***
ONLY when there is a 2ary bacterial infection
Dx of heaves***
History/PE: -increased expiratory effort -crackles/EXPIRATORY wheezes -lack of fever** -normal WBC count and fibrinogen Bronchoalveolar lavage: -well-preserved neuts** Response to bronchodilators
Tx of Heaves
NOT a cureable disease
Env. management: reduce dust**/allergen exposure
Corticosteroids: most effective
Bronchodilators (supportive)
most effective therapy for heaves
corticosteroids
Which aerosol therapy drugs get down to distal airways best?
AeroHippus, Torpex
