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VETM 422: Virology > equine viral diseases 2 - Nicole > Flashcards

equine viral diseases 2 - Nicole Flashcards

1
Q

Which subtypes of equine herpesvirus are prevalent?

A

EHV-1 and EHV-4

EHV-1 has a seroprevalence of 8-30%
EHV-4 has a seroprevalence of 85-100%

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2
Q

Which subtype of equine herpesvirus is the most clinically significant?

A

EHV-1

Causes respiratory signs, abortion storm, and encephalomyelitis.

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3
Q

How is EHV transmitted?

A

Direct or indirect contact or short distance aerosols.

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4
Q

What is the incubation period of EHV?

A

1-10 days

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5
Q

Where does EHV develop latency?

A

Trigeminal ganglia

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6
Q

What body systems can be affected by EHV?

A
  • Resp
  • Repro
  • Neuro
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7
Q

What are the clinical signs of EHV?

A
  • Biphasic fever!!!
  • Initially respiratory (mostly subclinical/mild)
  • Late term abortion storms (7-11 months)
  • Neurologic (paralysis, paraplegia, recumbance, head pressing, ataxia, loss of bladder function)
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8
Q

Which subtype of EHV causes neurological signs?

A

EHV-1 only

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9
Q

How does EHV cause abortion?

A
  • Viral antigens in placenta (can infect fetus)
  • Vasculitis
  • Thrombus (cuts off blood to fetus)
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10
Q

How is EHV diagnosed?

A
  • Nasopharyngeal swabs for PCR/virus isolaton
  • EDTA blood (virus is in buffy coat)
  • Aborted fetus tissue for histology or immunostaining
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11
Q

What percentage of EHV-1 strains are neurovirulent?

A

Only 10%

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12
Q

What causes certain EHV strains to be neurovirulent?

A

A point mutation in the viral polymerase genome

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13
Q

Describe how EHV vaccines induce immunity.

A

In susceptible horses, EHV enters through resp epithelium and it is spread to lymph nodes/CNS from there.

In protected/immune horses, immunity is induced at the respiratory tract which inhibits virus entry into repro and CNS.

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14
Q

What type of virus causes equine infectious anemia?

A

Retrovirus = lifelong infection.

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15
Q

Which animals are susceptible to EIA?

A

All members of equidae are affected but donkeys may be without clinical signs. Clinical disease occurs in horses and ponies.

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16
Q

How is EIA transmitted?

A
  • Mechanical transmission through fly vectors (mouthparts of biting insects)
  • Fomites
  • In utero
  • Via milk
  • Venereal
  • Aerosols
17
Q

Describe the pathogenesis of EIA.

A
  • Circulating immune complexes deposit causing vasculitis and glomerulonephritis
  • Infection and destruction of macrophages
  • Up-regulation of TNF-a, IL1 and IL6 contribute to fever, decreased bone marrow production of platelets and RBCs
  • Complement binds to RBCs causing them to undergo phagocytosis
18
Q

What are the three mechanisms for anemia caused by EIA?

A
  1. Decreased erythrocyte lifespan
  2. Depressed erythropoiesis
  3. Impaired flow of iron from macrophage to plasma
19
Q

What is unique about the fever caused by EIA?

A

Fever comes in recurrent episodes (peaks then goes away) - it is associated with viral replication.

20
Q

How is EIA diagnosed?

A

Serology or real time PCR

Serology:
Combine coggins test and ELISA: Coggins has high rate of false -ves, ELISA has high rate of false +ves. Want both tests to agree but if they don’t = immunoblot.

Real time PCR:
Does not detect carriers (no clinical signs)

21
Q

What is required to control EIA?

A

Adaptive immunity

22
Q

How is EIA controlled?

A

REPORTABLE DISEASE!

No vaccine available, infected animals are carriers for life (CFIA orders them destroyed or they undergo lifelong quarantine)

23
Q

How can you prevent EIA transmission within a stable?

A

Prevent transmission between horses
- Fly contol
- Single use needles
- Don’t breed positive ones (in utero, milk, venereal transmission)
- Prevent aerosol transmission

24
Q

What family of virus is west nile virus?

A

Flavivirus

Enveloped +sense ssRNA

25
Q

In which species is WNV enzootic?

A

Birds and mosquitoes (culex)

26
Q

Which animals develop high titers to WNV?

A

Peri-domestic avians (corvids) - american crows, yellow-billed magpies, jays.

High mortality in these species.

27
Q

What vectors allow WNV to be transmitted to humans and equines?

A

Bridge vectors = Aedes spp mosquitoes

28
Q

What are the dead end hosts of WNV?

A

Humans and equines

29
Q

How does WNV enter the CNS?

A

Entry via axonal retrograde transport along peripheral neurons into the spinal cord or hematogenous transport across BBB

30
Q

What are some potential mechanisms for WNV passing across the BBB?

A
  • Trojan horse model: intracellular transport within macrophages or neutrophils
  • Loss of integrity of the BBB: cytokine-mediated (TNF-α) or matrix metalloproteinases disruption of tight junctions and basement membranes
31
Q

What are the clinical signs of WNV?

A
  • Stumbling
  • In-coordination
  • Weak limbs
  • Partial paralysis
  • Muscle twitching
  • Death in some cases

Fever has occurred in less than one fourth of all confirmed equine cases

32
Q

How is WNV diagnosed?

A

Viremia induced by WNV is very short - diagnosis should look for neutralizing antibodies instead (serology).

33
Q

What can be done for WNV control?

A
  • Minimize mosquito bites
  • Vaccination (canarypox vectored vaccine, live-attenuated/inactivated WNV-yellow fever chimera)
34
Q

Equine herpesvirus (EHV)1 and 4 are different since:
A. EHV1 induces no clinical signs and EHV4 induces
encephalomyelitis
B. EHV4 induces no clinical signs and EHV4 induces coital exanthema
C. EHV1 establishes lifelong infection whereas EHV4 is cleared in 7-10 days
D. EHV1 induces no clinical signs and EHV4 induces
keratoconjunctivitis
E. Seroprevalence of EHV1 is lower than that of EHV4

A

E

35
Q

A common outcome of equine herpesvirus (EHV)1 and West Nile virus (WNV) infection is:
A. Colic
B. Anemia
C. Reproductive failure
D. Swollen limbs
E. Infection of leukocytes

A

E

36
Q

What is the possible clinical sign of equine infectious
anemia virus (EIAV) infection? Please mark the WRONG
answer.
A. Recurring episodes of disease
B. Colic
C. Fever
D. Depression
E. Nasal discharge

A

B

37
Q

Viremia of EHV1…
A. Follows lytic viral replication in trigeminal ganglion
B. Occurs after infection with neuropathogenic but not with non-neuropathogenic strains
C. Is mostly cell-associated
D. Is not involved in viral dissemination in the body
E. Is not evident in this infection

A

C

38
Q

Anemia due to equine infectious anemia (EIA) virus infection is
A. Due to increased erythrocyte life-span
B. Not related to compromised erythropoiesis
C. Due to destruction of erythroblasts
D. Non-immune mediated
E. Due to impaired flow of iron from macrophage to plasma

A

E

VETM 422: Virology (20 decks)

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