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As obligate nasal breathers, how do horses increase airflow during exercise?
dilate nares, nasal passages, and nasopharynx
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why should xylazine NOT be used as a sedative during endoscopy of upper respiratory?
- can affect swallowing and allow collapse of pharynx
- can affect ab/adduction of arytenoids
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what structures can be identified in the nasopharynx with endoscopy?
- ethmoid turbinates
- nasal septum
- dorsal pharyngeal recess
- soft palate
- opening for guttural pouch
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which cranial nerves run through the guttural pouch? what are other important nervous and vascular structures in this area?
- 9-12
- sympathetic trunk
- cranial cervical ganglion
- internal carotid a.
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where is the esophagus found?
as a potential space above the rima glottis in the larynx
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Of the 6 equine sinuses, which are the most affected by disease?
frontal and maxillary sinuses
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what is the most common etiology of primary sinusitis? which sinus most commonly?
- Streptococcus spp. (can follow viral infection)
- maxillary
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what is the most common cause of secondary sinusitis? which sinus?
- tooth root infection (PM4, M1,2,3)
- maxillary
- (other causes include cysts, fractures, tumors)
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what are common clinical signs associated with sinusitis? what is a sign of chronicity?
- uni or bilateral nasal discharge +/- foul smell
- ocular discharge/epiphora
- malaise, fever, inappetance
- chronic: facial deformity
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how can patency of nasolacrimal duct be assessed?
fluoroscein stain in the eye should be seen at nasal puncta
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if rads reveal fluid line in maxillary sinus, what is diagnosis? how is it treated?
- abscess (from tooth root abscess or other cause)
- start Abs (c/s pending)
- lavage w/balanced polyionic solution via trephine, sinoscopy, sinus flap, or balloon sinuplasty
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what is causative agent for Strangles? is this contagious?
- strep equi
- yes, highly contagious via inhalation/ingestion
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what is age of horse commonly affected w/strep equi? how long in incubation?
- young horse
- incubation 3-14 days
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what are major clinical signs associated with strangles?
- *fever*, depression, decr. appetite
- lymphadenopathy
- respiratory distress
- +/-nasal discharge (depends on which lnn. effected)
- +/- anemia if chronic
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which lymph nodes are typically affected by strangles? what clinical signs are seen depending on which is affected?
- submandibular - swell/rupture - drain out the nose
- retropharyngeal - swell - tracheal compression
- parotid - swell/rupture - drain out skin
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What do you do if horse presents with severe respiratory distress due to very enlarged retropharyngeal lymph nodes from strangles?
emergency tracheostomy
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what is cause of dysphagea in strangles patient?
cranial neuritis from guttural pouch infection if lymph nodes rupture here
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how is strangles diagnosed?
- anamnesis (new horse on property, travel)
- clinical signs
- endoscopy (pus) + *culture* nasal wash/abscess/GP
- PCR
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how is strangles treated?
- controversy but must isolate affected and exposed (highly contagious) + NSAIDs for fever/pain
- +/- penicillin (many will opt to "let it run its course")
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With strangles, when does shedding occur in relation to apparent fever?
- shedding 2-3 days after fever onset
- (best if catch first sign of fever then isolate before shedding)
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what is isolation protocol for horse with strangles? how long is it?
- no nose contact and tx last to avoid spread via staff
- isolate >2-3 wks following resolution of signs + negative culture
- (may persist in environment)
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Do horses develop lasting immunity after recovering from strangles?
- 75% get lasting immunity >5yrs
- 25% reinfect in months if not strong IgA
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what are potential complications of strangles?
- condroids
- dysphagia
- GP empyema
- bastard strangles
- purpura hemorrhagica
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if horse presents with clinical signs resembling strangles but culture of abscess reveals strep zooepidemicus (negative for staph equi), does horse still need to be isolated?
- no, strep zoo is not contagious
- strep zoo is *zoonotic*
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what are condroids? how does the horse present?
- inspisated pus
- may be asymptomatic/carrier - can spread to environment
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how are condroids diagnosed and treated?
- endoscopy of GP
- remove + lavage/instill penicillin gel
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what is bastard strangles? what are symptoms?
- hematogenous spread of strep equi -
- wt loss, pneumonia
- + reflect organ that becomes infected (neurological, colic/adhesions, lameness)
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how is bastard strangles treated? what is prognosis? is it zoonotic?
- long term Abs
- guarded prognosis
- zoonotic potential
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if horse has previous infection with staph equi, should you vaccinate him? why or why not?
check titers first- if titers high then NO vx - incr. risk of purpura hemorrhagica
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how is strangles prevented?
- vaccine protocols 2-3 doses (vx parent helps too)
- want mucosal immunity to block entry of agent
- isolate new horses at least 21d
- minimize farm traffic/good husbandry
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why should intranasal strangles vx not be given at same time as other IM vaccines?
intranasal highly immunogenic - if sneeze particles into IM site, abscesses
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is intranasal live or killed product? how many need to be given and how often?
- live
- initially 2-3 doses 2 weeks apart then annual booster
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when should the killed strangles vx be given to pregnant mares? how long does immunity last with this vx?
- 4-6 weeks before foaling
- ~6 months
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with pharyngeal lymphoid hyperplasia, how does horse present with the various stages?
- 0-3 performance may be effected but otherwise normal
- 4 - hemorrhagic, horse more symptomatic
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are horses with pharyngeal lymphoid hyperplasia febrile? systemically ill? anorexic? what age are they?
- no fever, no systemic illness
- normal appetite, BAR
- young, 1-2yrs
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what are the most common viral diseases of the upper respiratory?
- *equine influenza* - most frequently diagnosed
- herpes 1, 4
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(less common: EVA, rhinovirus)
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what are the two surface proteins for host specificity w/influenza?
- hemaglutinin (HA)
- neuraminidase (NA)
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what is the most common flu strain seen in horses?
- A1 and A2
- (in USA, A2 H3N8)
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what is age affected with flu? morbidity/mortality?
- young <3yrs
- high morbidity/low mortality
- comingled horses at greatest risk
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What tissue does flu have tropism for?
celiated respiratory epithelium in trachea/bronchi - damaged mucociliary clearance = prone to 2nd bacterial infection
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