Diseases of the Upper Respiratory Tract, Pt. 3 Flashcards
What is the guttural pouch?
bilateral outpouching of the Eustachian tube that connects the throat to the middle ear with medial and lateral segments containing sensitive vascular and nervous structures
What are 4 presumed functions of the guttural pouch?
- pressure equalization
- warming of air
- resonating chamber during vocalization
- cooling of blood directed to the brain during exercise
What causes Strangles?
Streptococcus equi subsp. equi
What are 3 factors that affect Streptococcus equi subsp equi infection? What is its incubation and shedding cycle like?
- horse age and immune status
- virulence
- management - number of horses in barn/pasture and their proximity
10-14 days (longer than viruses)
sheds 1-4 days after fever (still isolate!!) and lasts 2-6 weeks after purulent discharge —> carrier for years
What are the 5 steps to the pathogenesis of strangles? What is bastard strangles?
- entry of pathogen (inhaled) and attachment to cells of crypts of lingual and palatine tonsils
- spread to mandibular and suprapharyngeal LN with influx of neutrophils
- failure of neutrophils to kill bacteria due to hyaluronic acid capsule and SeM/Mac proteins
- bacterial streptolysin causes abscess formation by damaging cell membranes and activating plasminogen
- spread to other organs
abscesses in LN, thoracic, and abdominal organs
What are 6 common clinical signs associated with strangles?
- fever
- lethargy, decreased appetite
- lymph node abscess formation and rupture
- purulent nasal discharge
- cough
- respiratory distress
What are the 3 main complications associated with strangles?
- bastard strangles - metastasis
- purpura hemorrhagica and myositis - immune-mediated swelling of the liegs and tissue necrosis
- carriers - GP, sinus, decreased clearance (no clinical signs, acts as a source of infection to a herd)
What is commonly seen in the guttural pouch in strangles?
- irritation
- empyema: accumulation of pus
- chondroids: “pus stones”
What general techniques are used to diagnose strangles?
- hematology and biochemistry
- imaging: endoscope (upper airways, GP) and radiograph/ultrasound (metastasis)
What is the preferred specific technique used to diagnose strangles?
qPCR of nasopharyngeal wash (recover more fluid)
- swab
- aspirate of abscess
- guttural pouch lavage of possible carriers
Why is it uncommon to diagnose strangles with a culture?
- takes about a week
- typically overgrown by other bacteria
(can be done in parallel of other tests)
How is strangles infection prevented?
- quarantine new and returning horses
- screen temperatures and serology
(reportability depends on state)
What should be done during an outbreak of strangles? When are horses able to be released?
- isolate and stop movement of horses
- biosecurity using a traffic light system
- screen for carrier status with qPCR and serology
if they test negative on 3 qPCR tests in 3 weeks
What 2 vaccines are available for strangles? What do they do?
- INTRANASAL - MLV, given last due to possible transient clinical signs, like abscess formation
- INTRAMUSCULAR - killed, given in hindquarters due to possible local reaction
decrease the likelihood of spread and severity of clinical signs
Are horses vaccinated during an outbreak of strangles? Why or why not?
NO
can lead to immune reactions, like purpura hemorrhagica
What is the most common lineup for treatment of strangles?
- supportive care
- topical treatments for abscess maturation and drainage
- NSAIDs for pain, fever, and inflammation
- preventative tracheostomies
Why is the use of antimicrobials for strangles controversial? When are they used?
not usually needed since the horse usually clears infection by itself and they tend to delay abscess maturation and immunity
- respiratory distress
- bastard strangles
- purpura hemorrhagica
- carriers
What is the best antimicrobial for treating strangles? What is another option?
cephalosporins —> Ceftiofur IM every 4 days
Penicillin 30-35 mLs, BID
What are the most common clinical signs associated with guttural pouch empyema? How is it diagnosed?
- irritation
- accumulation of pus
- chondroids
- cranial nerve issues
endoscopy, qPCR, or radiographs (fluid line, chondroids)
What conservative management is recommended for guttural pouch empyema? What if this doesn’t work?
- lavage or basket retrieval
- saline, acetylcysteine, penicillin gel
- testing
surgery
(good prognosis)
What is guttural pouch typmany? What is the most common cause?
air in the guttural pouch causes distension, typically due to structural or functional issues with the auditory tube or pharyngeal ostium of the GP
What age, breed, and gender most commonly develop guttural pouch tympany?
birth to 1 year old
Arabian, Paint, and German Warmbloods
fillies»_space;> colts
What are the 5 most common clinical signs associated with guttural pouch tympany?
- bilateral marked, fluctuating, air-filled swelling nead the parotid and ventral laryngeal area (Bullfrog)
- snoring
- severe dyspnea
- aspiration pneumonia
- secondary infection
What 4 things are typically seen on endoscopy in cases of guttural pouch tympany?
- collapse of nasopharyngeal roof
- asymmetry
- deflation when scope inserted
- mucus/pus in pouch
What 2 things are commonly seen on radiographs in cases of guttural pouch tympany?
- enlarged GP
- possible fluid line
What conservative treatment is recommended for guttural pouch tympany? What is performed if this does not work?
insertion of a 14 g or foley catheter into the GP to let the air out
- UNILATERAL: medial septum fenestration
- BILATERAL: fistula towards the pharynx
What 3 fungi cause guttural pouch mycosis? What are the 2 most common sites of their infection?
- Aspergillus fumigatus
- Aspergillus nidulans
- Candida spp
- roof of the medial compartment over the petrous temporal bone and internal carotid artery
- lateral wall of the lateral compartment over the external carotid and maxillary arteries
What do the fungi in guttural pouch mycosis commonly form in the GP? What risk does this lead to?
diphtheritic membrane formation attached closely to underlying structure causes erosion
arterial rupture and nerve dysfunction
What are the 2 most common clinical signs associated with guttural pouch mycosis?
- mild intermittent unilateral epistaxis followed by potentially fatal massive hemorrhage
- neurological deficits
What 4 neurological deficits are most commonly seen with guttural pouch mycosis?
- dysphagia - CN 9-11
- left laryngeal hemiplegia - CN 10
- Horner syndrome
- stiffness, pain
How is guttural pouch mycosis diagnosed?
- history and clinical signs
- endoscopy
- contrast arteriography
What medical and surgical treatments are recommended for guttual pouch mycosis?
oral or local antifungals - more risky and lengthy
vascular occlusion with balloons, coils, or nitinol plugs
What is temporohyoid osteoarthropathy? What is thought to be the cause?
progressive disease of the middle ear, affected the styloid where it joins the temporal bone at the typanohyoid cartilage
infection/inflammation causes the joint to undergo degeneration, which leads to proliferation, bony fusion, and fracture
What are the 5 most common clinical signs of temporohyoid osteoarthropathy? What are the major risk factors?
- pain
- head tossing
- resistance under saddle
- sudden vestibular disease
- facial nerve paralysis
recent oral exams or floating
How is temporohyoid osteoarthropathy diagnosed?
- radiographs
- endoscopy
- CT
look for enlargement near the stylohyoid
What medical and surgical treatments are recommended for temporohyoid osteoarthropathy?
systemic antimicrobials, NSAIDS, supportive care (treat eye ulcers)
ceratohyoidectomy or partial stylohyoidetomy to remove parts of the stylohyoid apparatus
After an outbreak of strangles in a stable of 100 horses, what number of horses do you expect to become inapparent carriers?
a. 30
b. 50
c. 20
d. 10
D
10% of 100 = 10
Which of the following statements is true?
a. Strep equi equi is a normal commensal bacteria of the equine respiratory tract
b. Strep equi equi is NOT a normal commensal bacteria of the equine respiratory tract
B
it is a primary pathogen, unlike Strep equi zooepidemicus
