Exam #4: Equine Respiratory Pt. 2 Flashcards
DDx? 7 wk old foal with throat latch area swelling, dyspnea, stridor, mucopurulent nasal discharge, fever, tachypnea (6)
> Lymphadenopathy = bacterial (Strep), viral/inflam, neoplasia
Guttural pouch disease - tympany, empyema
Allergic reaction = previously sensitized older horses
Parotid gland inflammation
Severe lymphoid hyperplasia
Cyst
Goiter or thyroid tumor
Neoplasia
Diagnostics for suspected strangles
1) CBC
2) Rads
3) U/S
4) Tracheal fluid analysis and culture
5) Aspirate swelling
6) Chem panel = creatinine, albumin, Na+, K+, Cl-, TCO2 (proxy for bicarb) = previous renal damage (using aminoglycosides), acid-base
What happens with K+ during acidic and alkalotic processes?
- Acidotic = exchange H+ for K+ intracellularly = blood becomes hyperkalemic
- Alkalotic = expect K+ to move intracellularly, look artificially hypokalemic
Which is a less contaminated tracheal fluid sample - endoscopic or percutaneous?
Percutaneous
Initial treatment for strangles suspected animals
- K penicillin (IV, needs to be dosed more frequently)
- Rifampin = concentrates in WBC’s
- Banamine
- IV fluids to correct dehydration
- Hot pack swelling
+/- Tracheostomy with severe dyspnea
PaCO2 and PaO2 that may indicate hypoxemia and the need for a tracheostomy
- PaCO2 > 50 (hypoventilation)
- PaO2 < 80
Etiologic agent for “strangles” - who does it commonly affect?
> Strep equi var. equi
- Gram + B-hemolytic Strep
+ URT inflammation, LN abscessation, “bastard” or metastatic strangles
*Primarily affects foals and young horses
- Most horses develop immunity (4-5+ years)
Transmission, incubation period, and pathogenesis of “strangles”
- Direct contact with infected or subclinical shedders
- Indirect contact with contaminated (nasal discharge, pus from LN’s) fomites
- Incubation period = 3-14 days = disease can develop QUICKLY
- Ingested/inhaled and organism adheres to buccal/nasal mucosa
- Translocates below mucosa to local lymphatics, attracts neutrophils, disseminates
Which provides better immunity - natural strangles infection or Strep vax?
Natural infection = generates mucosal cell-mediated and humoral immunity
Main pathogenic factor (what vax and diagnostic testing targets) for strangles
SeM protein = anti-phagocytic
Diagnosis of strangles
- History
+ Clinical signs - Culture of exudate from LN, nasopharyngeal swab, guttural pouch
- Screening tests = PCR on nasopharyngeal swab/wash or exudate, serology (ELISA for SeM protein)
- Don’t detect current or viable infections
What should you not do if your strangles serology/titers show up as > 1:3200
DO NOT VACCINATE for strangles - may induce immune mediated vasculitis (purpura hemorrhagica)
What can serology of strangles do for you?
> ELISA for SeM protein
- Tells you about recent, but not current infections
- May determine the need for vax (< 1:3200)
- May ID animals at risk for purpura hemorrhagica (5-digit titers)
- HIGH titers may give evidence of bastard/metastatic abscessation
Which strangle-horse situations do and don’t we treat with antimicrobials?
> DON’T TREAT? Let natural disease progress
- Early clinical signs, no abscesses
- No sign the animal is compromised or has a complicated infection
> TREAT?
- Any horse with signs of compromise - fever, ongoing throat latch or LN enlarging, anorexia, dyspnea
+/- Horses exposed to strangles to prevent “seeding” of lymph nodes
- Purpura hemorrhagic + corticosteroids
- Bastard strangles
How do we treat uncomplicated strangles cases?
- Open, drain, and flush
- Keep environment clean to avoid contamination
- Hot packing to enhance maturation and drainage of abscess
How do we treat purpura hemorrhagica?
High levels of antimicrobials + corticosteroids (decrease immune mediated vasculitis with Ag+Ab)
Prevention of strangles
- Isolate all new arrivals for 3 weeks
- Immediately isolate any infected horses = shedding occurs for 2- weeks post recovery
- Decontaminate infected fomites
- Rest pastures and paddocks for 3 weeks
- Divide horses into 3 groups if outbreak occurs: direct/indirect contact, presumed infected, not infected
- Screen horses with nasopharyngeal swab or wash with culture/PCR
What can you monitor if you are nervous an exposed horse will develop strangles?
Watch for a fever
How do we confirm a “cure” of strangles?
Three consecutive weekly PCR and culture by nasal swab or nasopharyngeal wash
If + = confirm source, Ex: guttural pouch wash
Is it a good idea to vaccinate in the face of a strangles outbreak?
No - could trigger purpura
Who do we vax and not vax?
- Horses previously infected = develop good immunity = don’t vax for at minimum, 1 year
- Vax healthy, afebrile horses w/ no nasal discharge
- Do NOT vax in the face of an outbreak
- OPTIMAL protection = systemic (IgG) and mucosal (IgA) responses
Which type of vaccine has been associated with purpura hemorrhagica?
Strangles extract vax
Similarities and differences between Strep equi and Strep zoo
+ BOTH = fever, nasal discharge, LN enlargment
- Pneumonia = zoo > equi
- Higher risk of outbreak = zoo
- Higher risk of purpura hemorrhagica = equi
Dx? 4 mo colt, cough, nasal discharge, abnormal bronchovesicular lung sounds, wheezes, crackles, fluid sounds in trachea, fever, tachypnea
Pneumonia - bacterial (Strep, R. equi)
Others = post-viral bronchiolitis, parasitic pneumonia (ascarids), inflammatory airway disease (wouldn’t have systemic signs)
What is an important diagnostic tool if you suspect parasitic pneumonia?
Fecal float
Interpretation of bronchial patterns, thickened bronchi, and increased alveolar opacity in cranial lung lobes
- Bronchial = suggests parasitic (others = infections, allergic)
- Alveolar opacity = bronchopneumonia
DDx for eosinophils seen on transtracheal wash (3)
1) Allergic or hypersensitivity (round bale feeding, dusty environments)
2) Parasitic etiology
3) Inflammatory airway disease
Deworming protocol for parasitic pneumonia
Deworm with ivermectin or panacur (fenbendazole), then repeat in 3 weeks
- Add on Banamine at deworming (risk colic)
- Deworm other weanlings in the group
Why is TMS not a great choice for Strep infections?
Doesn’t penetrate purulent material well
Good antimicrobial choice for bacterial pneumonia, other general tx
- Procaine pen (IM) = gram + and anaerobes
- Gentamicin = gram +
- Provide a clean environment for recuperation
- Supportive care = nutrition, fluids
- Rest
Common etiologic agents for bronchopneumonia in foals and adults
- Foals = Strep zoo, R. equi, Actinobacillus or E. coli due to septicemia
- Adults = Strep zoo
- Anaerobic infections = rare in foals
What diagnostic imaging modality is helpful with pneumonia?
U/S
Two parasites that like to migrate through the equine lung, WHO do they affect?
1) Parascaris equorum = foals and yearlings (develop immunity over time)
2) Dictyocaulus arnfieldi = adult horses and ponies (asymptomatic in donkey and mule reservoir)
Reservoir for Dictyocaulus arnfieldi
Asymptomatic donkeys and mules
Treatment of ascarids in foals
Dewormers and NSAID’s, then repeat in 3-4 weeks
Pathogenesis of Dictyocaulus arnfieldi
- Carrier mules/donkeys spread eggs on pasture
- Ingested, L3 travel through gut to lymphatics and blood
- Circulate through the lungs
- Matures to L5, development arrests but inflammation occurs
Dx of Dictyocaulus arnfieldi
\+ Cough, expiratory dyspnea, crackles and wheezes in dorsocaudal lung fields (indistinguishable from RAO and IAD) \+/- Peripheral eosinophilia - Eosinophils on tracheal wash - Fecal float - Necropsy
Treatment for Dictyocaulus arnfieldi
- Menbendazole
- Albendazole
- Ivermectin
- Moxidectin
*Repeat later = drugs don’t kill larvae
+ NSAID’s - Treat all animals in contact with donkeys and mules
Causative agent in immunocompromised foal bronchopneumonia
Pneumocystis carinii
Treatment of neonatal respiratory distress
- Humidified O2 = want PaO2 of 80-100
- Keep in sternal recumbency
- Coupage and suction
- Antimicrobials
+/- Antivirals - Ventilation if hypercapnic
- NSAID’s
- Supportive care
DDx for acute respiratory stress in foals born from dystocia (2)
1) Diaphragmatic hernia
2) Rib fracture + pneumothorax
DDx? Adult horse with recent shipment, anorexic, depressed, high fever, slow to move, small/dry fecal balls, GI sounds present, tachycardic, increased expiratory effort, no crackles or wheezes, nasal flare, inducible cough, exudate in trachea
Neutrophilic leukocytosis with left shift
> Pleuropneumonia and pleuritis
- Others = viral respiratory disease (EHV-1 or 4, influenza), early bacterial pneumonia, colic
- Primary started as pneumonia, then went to pneumonia
Diagnostics for pleuritis or pleuropneumonia
- History and clinical signs
- CBC
- Electrolytes
- Chem = creatinine, albumin
- U/S the thorax
- Thoracocentesis w/ cytology, gram stain, C&S (aerobic and anaerobic)
- Transtracheal or endoscopic tracheal wash
What should you suspect if you start to see a left shift on bloodwork?
Gram negative involvement (gram + alone usually don’t cause it)
What do we administer if we see endotoxemia or evidence of toxic change in neutrophils?
Banamine
Treatment of pleuritis or pleuropneumonia
- IV fluids
- Drain fluid via chest tube
- Antimicrobials = penicillin, gentamicin, +/- rifampin if abscesses are present
- Analgesia
- Anti-endotoxemic banamine
- Supportive care = hydration, consider oncotics (pleural effusion), nutrition, leg supports, good bedding to avoid laminitis
- Monitor vitals, hydration status, fecal output, attitude, appetite
- Repeat auscultation and U/S in the morning
Causes of equine pleural effusion
- Infectious = bacterial pneumonia (Mycoplasma), viral (EIA, EHI, EHV), fungal
- Neoplasia
- Trauma to thoracic duct, thoracic cavity
- Extension from pericarditis or peritonitis
- Liver disease or severe hypoalbuminemia
- CHF
Number one cause of septic pleuritis
> Extension of pneumonia or lung abscessation
- Etiology agents = Strep, Pasteurella, Actinobacillus, E. coli, Enterobacter, Bacteroides, Clostridia, Fusobacterium, etc.
- Others = thoracic trauma, esophageal trauma, penetration of stomach/esophagus with foreign body
Risk factors for pleuropneumonia (7)
1) Long distance transport
2) Strenous exercise
3) Viral respiratory tract infection
4) Surgery
5) General anesthesia
6) Systemic illness
7) Long term non-steroidal use
Do penicillin work on Mycoplasma? Why or why not?
NO - doesn’t have a cell wall
Complications from pleuropneumonia (6)
1) Abscesses and adhesions in the pleural space
2) Bronchotracheal fistulas
3) Laminitis
4) Thrombophlebitis
5) Infection in other organ systems, dissemination
6) Purpura hemorrhagicum
Dx? Tachypnea, increased respiratory effort, dyspnea, pleurodynia, hypophagia, lethargy, +/- fever, stiff gait, cough, nasal discharge, toxemia
Acute pleuropneumonia
Dx? Weight loss, exercise intolerance, +/- persistent tachycardia, intermittent fever, substernal/limb edema
Chronic pleuropneumonia
Why is cytology important if you suspect pleuropneumonia?
Helps rule out neoplasia
When is radiographs helpful in diagnosing pleuropneumonia?
More chronic cases
When do we perform a thoracotomy with regards to pleuropneumonia?
> As a salvage procedure = establish external drainage
- Chronic pleuritis
- Adhesions
- Pleural abscess
Dx? Biphasic fever, anorexia, lethargy, dry and harsh cough, watery to purulent nasal discharge, +/- muscle soreness, limb edema, painful glands under jaw
Lab = normocytic, normochromic anemia and leukopenia
Equine influenza
True or false - equine influenza vax can prevent viral infection of horses
FALSE - can attenuate clinical signs but doesn’t prevent infection
What aged horse is most at risk for influenza?
1-5 years old
Risk factors for influenza
- Age = 1-5 years old
- Travel
- Proximity to contagious horses
- Fomites
Transmission of equine influenza
HIGHLY CONTAGIOUS = spreads via inhalation of aerosolized droplets from coughing and snorting - OR - contact with contaminated fomites
Characteristic CBC findings of equine influenza
Normochromic, normocytic anemia + leukopenia
DDx = chronic inflammation
Complications from equine influenza
- Bacterial pneumonia
- Myositis
- Myocarditis
- Limb edema
- May predispose the animal to EIPH, IAD, or RAO
Diagnosis of equine influenza
- Virus isolation or PCR from nasopharyngeal swabs
- Stall side immunoassay (not great)
- Serology = paired titers
Treatment of equine influenza
Supportive = keep them hydrated, breathing easy
Control of equine influenza
- Isolation
- Sanitation
- Vax = IM inactivated or IN MLV
What should you remember about influenza vaccination and age?
DON’T vaccinate before 6 months of age
Dx? Fever (can be biphasic), lethargy, anorexia, nasal discharge (serous to mucopurulent), conjunctivitis, lymphadenopathy, edema, vasculitis
+/- Abortion, myelitis, neonatal foal death and chorioretinopathy
EHV 1 and 4
What is the more common and more severe herpes virus in horses - EHV-1, EHV-4
EHV-1 = more common and more severe
Control of EHV
- No vax that prevents infection = but CAN reduce shedding and abortion storms
- Biosecurity = hygiene, barrier precautions between affected and normal animals
