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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
Q

how is EHVM diagnosed indirectly using serology with ELISA?

A

measures IgG - type specific (EHV-1 vs EHV-4)

same limitations as virus neutralization

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26
Q

how is EHVM diagnosed directly using immunofluorescence?

A

its rapid, reasonably sensitive & specific

used on nasal/nasopharyngeal swabs or post-mortem tissues

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27
Q

how is EHVM diagnosed directly using virus isolization?

A

gold standard for diagnosis!!!

cytopathic effects in cell culture, can follow with PCR

currently more sensitive than IFA or PCR

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28
Q

what is the gold standard test for diagnosing EHVM?

A

virus isolation

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29
Q

what is the test commonly used to diagnose EHVM?

A

PCR for direct demonstration of the virus

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30
Q

how is EHVM diagnosed directly using PCR?

A

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

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31
Q

why is it hard to diagnose a latent infection of EHVM?

A

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

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32
Q

what should you do with a horse that is positive for EHVM?

A

isolate the animal!!! horses with neuro signs can shed the virus & transmit it directly (aerosol) or indirectly (fomites)

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33
Q

what treatment is used for EHVM?

A

no controlled studies - empiric treatment

anti-inflammatories (flunixin meglumine/glucocorticoids), anti-virals, & supportive care

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34
Q

why are glucocorticoids controversial for treatment use in horses with EHVM?

A

they may cause viral replication or reactivation - but no strong evidence (reaction only at 1mg/kg)

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35
Q

what is the anti-viral drug of choice for EHVM?

A

valacyclovir at 30mg/kg, PO, q8-12 hours

better bioavailability than acyclovir - prodrug of acyclovir

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36
Q

what should be included in your supportive care for EHVM?

A

deep stall bedding for recumbent animals, lubricate eyes, vaseline to perineum, catheterize bladder/evacuate rectum, sling, & IV fluids/other treatments as needed

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37
Q

what is the prognosis for recumbent horses with EHVM?

A

very poor

38
Q

how is EHVM prevented using vaccines?

A

it doesn’t protect the animal from EHVM but it can reduce viral shedding & help with control

39
Q

how is EHVM prevented using biosecurity?

A

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
Q

what does WNVE stand for?

A

west nile encephalomyelitis

41
Q

what causes west nile encephalomyelitis?

A

flavivirus - RNA virus

transmitted by mosquitoes

42
Q

what is the pathogenesis of west nile encephalomyelitis?

A

mosquitoes transmit the virus

causes necrosis of nervous tissue especially in the midbrain, brainstem, & lumbosacral spinal cord

polioencephalomyelitis!! gray matter disease!!

43
Q

T/F: ~90% of WNVE horses show no clinical signs

A

true

44
Q

what are the big clinical signs of west nile encephalomyelitis?

A

muscle fasciculations!!! fine & coarse fasciculations of face/neck, but muzzle & eyelids may be most notable

spinal ataxia - asymmetrical, can progress to recumbency

45
Q

what is the mentation like of an animal with west nile encephalomyelitis?

A

altered behavior/depressed attitude, weakness

46
Q

does west nile encephalomyelitis affect cranial nerves?

A

sometimes

47
Q

what is the progression of disease of west nile encephalomyelitis?

A

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
Q

what is the prognosis for west nile encephalomyelitis in a recumbent horse?

A

poor prognosis

49
Q

how is west nile encephalomyelitis diagnosed?

A

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
Q

what is the treatment for west nile encephalomyelitis?

A

supportive care, anti-inflammatories, & IV immunoglobulins (WNV hyperimmune plasma)

51
Q

how is west nile encephalomyelitis prevented?

A

mosquito control, surveillance, & vaccination

52
Q

when should you vaccinate for west nile encephalomyelitis?

A

before mosquito season!! duration of immunity & frequency of the vaccine is unclear

53
Q

T/F: west nile encephalomyelitis is a reportable disease

A

true

54
Q

what is equine encephalomyelitis (EEE/WEE/VEE)?

A

infectious viral disease of equids characterized by deranged consciousness, motor irritation, ataxia, paralysis, & high case fatality rate

55
Q

equine encephalomyelitis viruses can affect any part of the CNS - what aspects of the CNS are affected more? (gray matter/white matter)

A

gray matter

56
Q

what causes equine encephalomyelitis?

A

togaviruses - RNA viruses in the alphavirus genus of togaviridae

eastern, western, & venezuelan equine encephalitis viruses

57
Q

how many subtypes does EEE have?

A

6

58
Q

how many antigenic subtypes of WEE are there?

A

2 antigenic subtypes

59
Q

what kind of hosts are horses for EEE & WEE?

A

dead end hosts - they don’t result in sufficient viremia

60
Q

T/F: EEE/WEE/VEE can cause disease in humans

A

true

61
Q

what is the most important source of VEE?

A

horses

62
Q

of the viruses that cause equine encephalomyelitis, which carries the highest fatality rate for humans & horses?

A

EEE

63
Q

of the viruses that cause equine encephalomyelitis, which carries the lowest fatality rate for humans?

A

VEE

64
Q

what are the clinical signs for EEE/WEE/VEE?

A

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
Q

what are the terminal clinical signs for EEE/WEE/VEE?

A

dementia, paralysis, seizures, & coma leading to death

66
Q

T/F: EEE/WEE/VEE is reportable!!

A

true

67
Q

how is EEE/WEE/VEE diagnosed?

A

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
Q

what is the treatment for EEE/WEE/VEE?

A

anti-inflammatories, supportive care - same as WNV

69
Q

how is EEE/WEE/VEE prevented?

A

mosquito control, surveillance, & vaccination

70
Q

of EEE/WEE/VEE, what are we primarily vaccinating for?

A

EEE/WEE

may need to vaccinate > 1yr

71
Q

what is rabies?

A

highly fatal, rapidly progressive viral encephalomyelitis classically manifesting as motor irritation, ascending paralysis, & mania/dummy attitude

72
Q

what causes rabies?

A

neurotropic rhabdovirus

73
Q

how is rabies transmitted?

A

animal bites primarily - but occasionally by inhalation/ingestion

74
Q

what is the pathogenesis of rabies?

A

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
Q

what are the 3 syndromes of rabies?

A

prodromal form, furious form, & dumb form

76
Q

what are the signs associated with the prodromal form of rabies?

A

early signs mimic other diseases - lameness, colic, spinal ataxia

77
Q

what are the signs associated with the furious form of rabies?

A

hyperesthesia, muscle tremors, aggressive behavior, tenesmus, circling, self-mutilation, abnormal sexual activity

78
Q

what are the signs associated with the dumb form of rabies?

A

somnolence, stupor, paralysis, depression

79
Q

what clinical signs should alert you to suspect rabies?

A

change in behavior, hypersensitivity, choke (in cattle especially), abnormal phonation, self-mutilation, & abnormal aggression

80
Q

how is rabies diagnosed post-mortem?

A

fluorescent antibody test of the brain & detection of negri bodies

81
Q

T/F: rabies is a reportable disease

A

true

exercise care & follow regulations for submitting tissues as this is a public health risk

82
Q

what is the treatment for rabies?

A

supportive care until death or euthanasia

assumed all cases will die

83
Q

how is rabies prevented in horses?

A

avoid exposure, vaccination, annual booster recommended, core vaccine in TX

84
Q

how is rabies prevented in humans?

A

vaccination, proper PPE for handling neuro cases, keeping good records, & avoiding exposure

85
Q

what equine viral diseases are reportable that cause neurological disease?

A

EHVM, WNVE, EEE/WEE/VEE, & rabies

86
Q

what equine viral diseases that cause neurological diseases are core vaccines as designated by the AAEP?

A

EEE/WEE/VEE & rabies

87
Q

T/F: there is a vaccine for EHVM

A

false, there is none

88
Q

other than neurological signs, EHV-1 can cause what other clinical signs?

A

respiratory disease, abortion, & ocular disease

89
Q

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

A

true

90
Q

T/F: EHVM can affect horses of any age, but older horses may be more susceptible

A

true

LA DX & TX I (45 decks)

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