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LA DX & TX I > Exam 1 - Equine Neurology - Viral Diseases > Flashcards

Exam 1 - Equine Neurology - Viral Diseases Flashcards

1
Q

what is EHVM?

A

equine herpesvirus myeloencephalopathy

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2
Q

what is equine herpesvirus myeloencephalopathy?

A

acute viral disease of horses with worldwide distribution that causes a vasculitis in the central nervous system

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3
Q

what are other common names for EHVM?

A

equine herpes

rhinopneumonitis

rhino

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4
Q

what virus primarily causes EHVM?

A

equine herpesvirus 1

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5
Q

T/F: EHV-4 is a rare cause of EHVM

A

true

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6
Q

T/F: EHVM from EHV-4 is a reportable disease in Texas

A

true

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7
Q

what is the pathogenesis of EHVM?

A

neuropathogenic strain

vasculitis with thrombotic ischemia following endothelial infection

ischemic necrosis of brain, brainstem, or spinal cord

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8
Q

T/F: not all EHVM is caused by a neuropathogenic strain from a point mutation in DNA polymerase enzyme

A

true

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9
Q

T/F: EHVM causes direct damage to the neurons by the virus

A

false - damage comes from vasculitis

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10
Q

T/F: vaccination for EHV-1 does protect against EHVM

A

false - it doesn’t protect the animal

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11
Q

T/F: Nearly all horses are believed to have a latent infection of EHV by 1 year of age

A

true

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12
Q

Can the neuropathogenic strain of EHV cause latent infection?

A

yes

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13
Q

how is it proposed that EHVM develops in terms of a latent or lytic infection?

A

not clear

either:

new infection from lytic cycle or reactivation of latent infection

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14
Q

what is the signalment of horses affected by EHVM?

A

any age, breed, or sex

older horses may be more susceptible

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15
Q

what is the typical history of a patient with EHVM?

A

no premonitory clinical signs

biphasic fevers leading into neuro signs

sporadic or epidemic

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16
Q

when do clinical signs associated with EHVM appear?

A

1-10 days after infection/onset viremia with peak severity 2-3 days after the onset

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17
Q

what are the common clinical signs associated with EHVM?

A

highly variable

usually NO SKELETAL MUSCLE ATROPHY

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18
Q

what area of the spinal cord is most often affected with EHVM? what clinical signs are seen with this?

A

caudal segments of the spinal cord & sacral plexus

usually symmetrical ataxia, paresis, & spasticity that is worse in the hind limbs

sacral nerve involvement - bladder atony (incontinence, urinary retention) & perineal sensory deficits

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19
Q

there may be cranial nerve involvement with EHVM - if there is, what is typically involved?

A

most commonly head tilt - vestibulocochlear

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20
Q

how is EHVM diagnosed?

A

history (outbreak) & clinical signs (sacral nerve involvement - loss of anal tone, urine scalding - nature of progression, & cranial nerve involvement)

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21
Q

how is EHVM diagnosed indirectly using hematology?

A

early leukopenia followed by viral infection, non-specific evidence, not very useful

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22
Q

how is EHVM diagnosed indirectly using CSF analysis?

A

increase in protein & WBC concentrations

xanthochromia!!! - increase in protein & RBC breakdown

EHV-1 antibodies in CSF indicate exposure but is not confirmatory

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23
Q

how is EHVM diagnosed indirectly using serology with complement fixation?

A

measures IgM - rises & falls rapidly

rising CF titers separated by 10-14 days is good evidence

single high titer in a clinically affected horse is useful

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24
Q

how is EHVM diagnosed indirectly using serology with virus neutralization?

A

measures IgG - rises more slowly & persists longer

not clinically useful

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25
how is EHVM diagnosed indirectly using serology with ELISA?
measures IgG - type specific (EHV-1 vs EHV-4) same limitations as virus neutralization
26
how is EHVM diagnosed directly using immunofluorescence?
its rapid, reasonably sensitive & specific used on nasal/nasopharyngeal swabs or post-mortem tissues
27
how is EHVM diagnosed directly using virus isolization?
gold standard for diagnosis!!! cytopathic effects in cell culture, can follow with PCR currently more sensitive than IFA or PCR
28
what is the gold standard test for diagnosing EHVM?
virus isolation
29
what is the test commonly used to diagnose EHVM?
PCR for direct demonstration of the virus
30
how is EHVM diagnosed directly using PCR?
tests for EHV-1 or EHV-1 neuropathic, reasonably sensitive, rapid, quantitative with real time PCR nasal swabs are better than nasopharyngeal & synthetic swabs are preferable to cotton
31
why is it hard to diagnose a latent infection of EHVM?
they don't have any clinical signs, usually test negative, under the radar of the immune system, so they don't express viral-encoded proteins
32
what should you do with a horse that is positive for EHVM?
isolate the animal!!! horses with neuro signs can shed the virus & transmit it directly (aerosol) or indirectly (fomites)
33
what treatment is used for EHVM?
no controlled studies - empiric treatment anti-inflammatories (flunixin meglumine/glucocorticoids), anti-virals, & supportive care
34
why are glucocorticoids controversial for treatment use in horses with EHVM?
they may cause viral replication or reactivation - but no strong evidence (reaction only at 1mg/kg)
35
what is the anti-viral drug of choice for EHVM?
valacyclovir at 30mg/kg, PO, q8-12 hours better bioavailability than acyclovir - prodrug of acyclovir
36
what should be included in your supportive care for EHVM?
deep stall bedding for recumbent animals, lubricate eyes, vaseline to perineum, catheterize bladder/evacuate rectum, sling, & IV fluids/other treatments as needed
37
what is the prognosis for recumbent horses with EHVM?
very poor
38
how is EHVM prevented using vaccines?
it doesn't protect the animal from EHVM but it can reduce viral shedding & help with control
39
how is EHVM prevented using biosecurity?
28 days isolation - don't move off premises or within premises once isolated separate gear/tack disinfect in-contact surfaces quarantine new arrivals minimize stress
40
what does WNVE stand for?
west nile encephalomyelitis
41
what causes west nile encephalomyelitis?
flavivirus - RNA virus transmitted by mosquitoes
42
what is the pathogenesis of west nile encephalomyelitis?
mosquitoes transmit the virus causes necrosis of nervous tissue especially in the midbrain, brainstem, & lumbosacral spinal cord polioencephalomyelitis!! gray matter disease!!
43
T/F: ~90% of WNVE horses show no clinical signs
true
44
what are the big clinical signs of west nile encephalomyelitis?
muscle fasciculations!!! fine & coarse fasciculations of face/neck, but muzzle & eyelids may be most notable spinal ataxia - asymmetrical, can progress to recumbency
45
what is the mentation like of an animal with west nile encephalomyelitis?
altered behavior/depressed attitude, weakness
46
does west nile encephalomyelitis affect cranial nerves?
sometimes
47
what is the progression of disease of west nile encephalomyelitis?
improvement in 3-5 days (often) - some may have recrudescence after 7-10 days most fully recover within 1-6 months can have residual ataxia, limb paresis, & exercise intolerance
48
what is the prognosis for west nile encephalomyelitis in a recumbent horse?
poor prognosis
49
how is west nile encephalomyelitis diagnosed?
clinical signs/history/vaccine status serology - IgM capture ELISA titer > 1:400, lasts about 6 weeks post-mortem detection of west nile virus in the brain using IHC, PCR, or virus isolation
50
what is the treatment for west nile encephalomyelitis?
supportive care, anti-inflammatories, & IV immunoglobulins (WNV hyperimmune plasma)
51
how is west nile encephalomyelitis prevented?
mosquito control, surveillance, & vaccination
52
when should you vaccinate for west nile encephalomyelitis?
before mosquito season!! duration of immunity & frequency of the vaccine is unclear
53
T/F: west nile encephalomyelitis is a reportable disease
true
54
what is equine encephalomyelitis (EEE/WEE/VEE)?
infectious viral disease of equids characterized by deranged consciousness, motor irritation, ataxia, paralysis, & high case fatality rate
55
equine encephalomyelitis viruses can affect any part of the CNS - what aspects of the CNS are affected more? (gray matter/white matter)
gray matter
56
what causes equine encephalomyelitis?
togaviruses - RNA viruses in the alphavirus genus of togaviridae eastern, western, & venezuelan equine encephalitis viruses
57
how many subtypes does EEE have?
6
58
how many antigenic subtypes of WEE are there?
2 antigenic subtypes
59
what kind of hosts are horses for EEE & WEE?
dead end hosts - they don't result in sufficient viremia
60
T/F: EEE/WEE/VEE can cause disease in humans
true
61
what is the most important source of VEE?
horses
62
of the viruses that cause equine encephalomyelitis, which carries the highest fatality rate for humans & horses?
EEE
63
of the viruses that cause equine encephalomyelitis, which carries the lowest fatality rate for humans?
VEE
64
what are the clinical signs for EEE/WEE/VEE?
fever - usually precedes neuro signs irritative signs - restlessness, hypersensitive, tremors, may see blindness, circling with ataxia progression to depressive signs - sleepy, obtunded, head held low, & unnatural posture
65
what are the terminal clinical signs for EEE/WEE/VEE?
dementia, paralysis, seizures, & coma leading to death
66
T/F: EEE/WEE/VEE is reportable!!
true
67
how is EEE/WEE/VEE diagnosed?
clinical signs/history - vaccine status is important serology - IgM titer > 1:400, CSF is more convincing than serum, or IgG 4 fold increase in acute/convalescent serum post-mortem detection in brain - IHC, PCR, & virus isolation
68
what is the treatment for EEE/WEE/VEE?
anti-inflammatories, supportive care - same as WNV
69
how is EEE/WEE/VEE prevented?
mosquito control, surveillance, & vaccination
70
of EEE/WEE/VEE, what are we primarily vaccinating for?
EEE/WEE may need to vaccinate > 1yr
71
what is rabies?
highly fatal, rapidly progressive viral encephalomyelitis classically manifesting as motor irritation, ascending paralysis, & mania/dummy attitude
72
what causes rabies?
neurotropic rhabdovirus
73
how is rabies transmitted?
animal bites primarily - but occasionally by inhalation/ingestion
74
what is the pathogenesis of rabies?
virus travels from the site of inoculation to the CNS via axons, then peripherally to other organs via the nerves viremia may occur after infection - can be shed in milk & feces
75
what are the 3 syndromes of rabies?
prodromal form, furious form, & dumb form
76
what are the signs associated with the prodromal form of rabies?
early signs mimic other diseases - lameness, colic, spinal ataxia
77
what are the signs associated with the furious form of rabies?
hyperesthesia, muscle tremors, aggressive behavior, tenesmus, circling, self-mutilation, abnormal sexual activity
78
what are the signs associated with the dumb form of rabies?
somnolence, stupor, paralysis, depression
79
what clinical signs should alert you to suspect rabies?
change in behavior, hypersensitivity, choke (in cattle especially), abnormal phonation, self-mutilation, & abnormal aggression
80
how is rabies diagnosed post-mortem?
fluorescent antibody test of the brain & detection of negri bodies
81
T/F: rabies is a reportable disease
true exercise care & follow regulations for submitting tissues as this is a public health risk
82
what is the treatment for rabies?
supportive care until death or euthanasia assumed all cases will die
83
how is rabies prevented in horses?
avoid exposure, vaccination, annual booster recommended, core vaccine in TX
84
how is rabies prevented in humans?
vaccination, proper PPE for handling neuro cases, keeping good records, & avoiding exposure
85
what equine viral diseases are reportable that cause neurological disease?
EHVM, WNVE, EEE/WEE/VEE, & rabies
86
what equine viral diseases that cause neurological diseases are core vaccines as designated by the AAEP?
EEE/WEE/VEE & rabies
87
T/F: there is a vaccine for EHVM
false, there is none
88
other than neurological signs, EHV-1 can cause what other clinical signs?
respiratory disease, abortion, & ocular disease
89
T/F: EHV-4 is a rare cause of EHVM
true
90
T/F: EHVM can affect horses of any age, but older horses may be more susceptible
true

LA DX & TX I (45 decks)

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