Lecture 35

Question 1

What are the clinical signs of cerebral/cortical disease?

Answer 1

-altered behavior, mentation, and/or consciousness
-mild weakness
-mild depression
-aimless wandering
-seizures
-blindness with normal PLRs

Question 2

Which metabolic causes should be ruled out in the event of cortical signs?

Answer 2

-hypoglycemia
-hyperglycemia
-hepatoencephalopathy (elevated ammonia)
-GI causes of elevated ammonia
-hyponatremia
-hypocalcemia
-uremia
-hyperlipidemia

Question 3

What is the vector for west nile virus transmission?

Answer 3

mosquito

Question 4

What are the signs of west nile virus in horses?

Answer 4

-weakness and depression
-stumbling or incoordination
-possible fever
-spinal deficits
-myeloencephalitis
-facial muscle twitching (muzzle)
-seizures
-recumbency
-death

Question 5

What are the clinical signs of EEE/WEE?

Answer 5

-biphasic fever on days 2 and 6
-stiffness
-hyperesthesia
-aggression
-excitability
-continuous chewing
-head pressing
-wandering
-recumbency
-seizures
-death

Question 6

How are viral encephalitis cases diagnosed?

Answer 6

-clinical signs
-serum antibodies; capture ELISA for IgM, single high IgG titer
-post-mortem findings

Question 7

What is the treatment for viral encephalitis?

Answer 7

-nursing and supportive care
-IV fluids for dehydration
-NSAIDs to reduce brain swelling
-hyperimmune plasma for west nile

Question 8

How is west nile, EEE, and WEE prevented?

Answer 8

-reduce mosquito populations by removing stagnant water sources
-mosquito dunks
-core vaccine; biannual vaccination

Question 9

What are the characteristics of equine herpesvirus?

Answer 9

-found in horses worldwide
-causes “rhino” or rhinopneumonitis
-infects horses, mules, donkeys, zebras, giraffes, and camelids
-does NOT affect people, cows, dogs, or cats
-reportable in some states

Question 10

What are the characteristics of equine herpes myeloencephalopathy?

Answer 10

-causes necrosis of nervous tissue
-due to a “neurotropic” strain
-genetic variant is more contagious and causes more virus in the blood

Question 11

What are the effects of equine herpes virus on the tissues?

Answer 11

-endotheliotrophic; spreads via circulating mononuclear cells
-causes necrotic vasculitis
-causes hypoxia and ischemia to adjacent CNS tissue

Question 12

What are the charactersitics of equine herpes virus 1 presentation?

Answer 12

-incubation period of 1 to 10 days
-first sign is often fever
-can have asymptomatic shedders
-causes respiratory and/or neuro. signs
-can shed virus for 14 to 21 days

Question 13

What are the characteristics of latent infection with EHV 1?

Answer 13

-remains dormant in upper resp. lymph nodes and trigeminal ganglia
-typically non-neurotropic but can be neurotropic

Question 14

How is equine herpes virus infection diagnosed?

Answer 14

*EHV-1 specific PCR
-blood and/or nasal swab collected from both nostrils

*CSF
-increased protein and xanthochromia
-PCR

*virus isolation

Question 15

What are the clinical signs of equine herpes myeloencephalopathy/EHM?

Answer 15

-hindlimb ataxia and weakness
-weak tail tone
-urinary and fecal incontinence
-possible cranial nerve deficits
-possible cortical signs

Question 16

What is the treatment for EHM?

Answer 16

-isolation procedures
-nursing care
-catheterize bladder as needed
-NSAIDs such as DMSO; NO STEROIDS!
-antibiotics to prevent secondary infections

Question 17

What are the characteristics of antiviral treatment for EHM?

Answer 17

-acyclovir or valacyclovir
-potent inhibitor of herpes DNA polymerases
-acyclovir has low oral bioavailability; want to use IV form
-valacyclovir has good bioavailability orally or IV
-very expensive
-not effective in every animal

Question 18

What are the steps to EHV 1 prevention?

Answer 18

-vaccination to decrease resp. form, shedding, and abortions
-isolation of clinical horses
-frequent rectal temperatures on exposed horses
-quarantine facility for 3 weeks after last horse has fever

Question 19

What are the characteristics of rabies?

Answer 19

-should be suspected in any neurologic case
-incubation period ranges from 9 days to 1 year
-post-mortem diagnosis only
-reportable

Question 20

What are the characteristics of rabies prevention in horses?

Answer 20

-annual core vaccine available
-if exposed, isolate horses and observe for neuro. signs
-vaccinated horses are isolated for 45 days; unvaccinated horses for 6 months

Question 21

What are the characteristics of idiopathic epilepsy in egyptian arabians?

Answer 21

-onset between 2 days and 6 months of age
-rule out other causes of seizures
-self-limiting; disappears by 1 to 2 years of age

Question 22

What are the drugs used for seizure management?

Answer 22

*emergency/infrequent seizures:
-diazepam
-midazolam
-IV phenobarbital to effect

*long term control:
-phenobarbital +/- gabapentin
-potassium bromide
-levetiracetam

Question 23

What are possible iatrogenic triggers of seizures?

Answer 23

-air embolism injections
-carotid injections

Question 24

What are the characteristics of narcolepsy?

Answer 24

-uncontrolled episodes of cataplexy and sleep
-triggered by benign activity, NOT exercise
-normal cardiovascular, resp., and facial/eye responses maintained

Question 25

How is narcolepsy diagnosed?

Answer 25

-rule out other causes of cataplexy -EEG and EMG during an episode -physostigmine test -treat for response with imipramine

Question 26

What are the characteristics of sleep deprivation in horses?

Answer 26

-can only achieve REM sleep when laying down -will not lay down to sleep when hospitalized, in pain, sick, or otherwise uncomfortable