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VETM 422 Virology > Lecture 15: Equine Viruses > Flashcards

Lecture 15: Equine Viruses Flashcards

1
Q

What are the viral features of equine influenza

A

Equine Influenza
Orthomyxoviridae:
* Influenza
* 8 segments
* ssRNA
* 11 proteins

  • Influenza A: Equine-1 H7N7, Equine-2 H3N8
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2
Q

What are 2 ways that influenza virus evolves

A
  • Evolution via mutation or genetic reassortment
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3
Q

What is the predominant equine influenza subtype

A
  • Influenza A:
    o A-1 H7N7 (rare)
    o A-2 H3N8 (most)
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4
Q

Hosts of equine influenza

A

Hosts: Equids (horse, donkey, mule) also dogs

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5
Q

Does equine influenza cross the placental membrane

A

no

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6
Q

How is equine influenza transmitted

A

Transmit: contagious via aerosols
* Viral excretion during incubation periods (1-3d) and 5 days after clinical signs start
* Vaccinated and infected viruses can shed
* Virus excretion 7-10d (important for dx)

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7
Q

What are the target cells and mechanism of damage of equine influenza virus

A

Pathogenesis:
* Target: ciliated epithelial cells and alveolar macrophages
* Viral replication: upper and lower respiratory tract epithelium
* Damage: Destroy ciliated epithelium

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8
Q

What are the clinical signs of equine influenza virus

A

Clinically: return to athletic activity in 50-100d (resolve in 2-3wk) – morbidity 90%, mortality 20%
* High fever
* Depression (4-5d)
* Anorexia
* Red nasal mucosa/conjunctivitis/serous mucopurulent discharge
* Harsh dry paroxysmal cough
* Laryngitis
* Bronchitis
* Bronchointersitial pneumonia (acute fibrinopurulent pneumonia)
* Pulmonary congestion and edema
* Secondary bacterial infection (if signs persist for 10d)
* Fatal in <2wk foal: premature placental separation and dystocia (fetal hypoxia)

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9
Q

What is the importance of pox virus in vet med

A

Vector for vaccine (equine influenza and rabies recombinant vaccines)

Cause infections: cowpox

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10
Q

How to diagnose equine influenza

A

Dx: clinical signs (fast spreading respiratory infection/high fever/cough/depression)

  • Virus isolation: inoculate (into amniotic or allantoic space) and incubate 9-11d embryo for 3-4d
    o Collect amniotic or allantoic fluid
    o Use hemagglutination inhibition test assay add virus and RBC
     Positive: agglutination
     Negative: RBC form pellet in the bottom (no agglutination)
     The last inhibition indicates the titre strength (1:64 vs 1:8 – different serial dilution strengths0
  • RT-PCR: separate sub-lineages and identify clades
    o H3N8 lineages: American (sub-lineage: Kentucky, South American, Florida – clade 1 and 2) and Eurasian
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11
Q

What samples do you need to diagnose equine influenza

A
  • Sample via nasopharyngeal swab/blood
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12
Q

How to control equine influenza

A
  • Vaccine:
    o Killed: from European and American lineage of H3N8
     Any killed vaccine not very effective
    o modified live: Intranasal, cold adapted
     effective
    o recombinant: recombinant canary pox vector based equine influenza vaccine
  • Pregnant mare – vaccinate 2-6wk before parturition (give maternal Ig to foal)
  • Foal: vaccination before 6wk old can interfere with maternal antibodies
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13
Q

How does the modified live equine influenza vaccine work

A

o modified live: Intranasal, cold adapted (replicate in the upper but not lower respiratory tract due to temperature difference = induce mucosal immunity in upper resp)
 effective
 Can have marker: delete gE glycoprotein + use 2 ELISAs to identify infected vs vaccinated

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14
Q

How does the recombinant equine influenza vaccine work

A

o recombinant: recombinant canary pox vector based equine influenza vaccine
 insert HA gene into Pox genome – Pox virus replicated and induced antibody against HA
 When infected – immune response against both HA and NP
 Act as a DIVA vaccine and result in immunity to HA proteins
* When using non DIVA vaccine = immunity to some of each HA and NP
 DIVA vaccination strategy: vaccinated animals only immune to HA
* Vaccinated and infected animals immune to both HA and NP

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15
Q

What is a vaccination buffer

A
  • Vaccination buffer zone: vaccinate the population to insulate naïve animals from virus
    o Infected animals will shed but will induce lower shedding in other vaccinated animals – reduce likelihood of transmission
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16
Q

What are a few non-vaccine methods to prevent equine influenza

A
  • Biosecurity
    o Isolate and vaccinate new animals
    o Isolate infected animals 50m away from other horses
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17
Q

How to treat equine influenza

A
  • Treatment: amantadine, rimantadine – not effective, drug resistance
    causes CNS effect
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18
Q

What are the viral features and taxonomy of equine viral arteritis

A

Taxonomy: (+)ssRNA, enveloped
* Order: Nidovirales
* Family: Arteriviridae
* Genus: Arterivirus

19
Q

What are the hosts of equine viral arteritis

A

Host: Equids +/- SA Camelids

20
Q

Where is equine viral arteritis found

A

Geography: Worldwide except Iceland and Japan

21
Q

How is equine viral arteritis transmitted

A

Transmit: mainly in breeding facilities (semen collection/fomites) – contaminated frozen semen
* 30-60% infected stallions become persistently infected (carrier without clinical signs)
* Can cross placenta
* Some horizontal transmission (fomite/personal/aerosol) – minor
* Can shed in urine

22
Q

What is the incubation period for equine viral arteritis

A
  • Incubation: 1-14d
23
Q

What is the pathogenesis of equine viral arteritis

A

Pathogenesis:
* Infect alveolar macrophages, type 2 pneumocytes, pulmonary endothelial cells
* Circulate in monocytes to LN
* Infect endothelial cells and myocytes = damage blood vessels
* Distribute to body systems

24
Q

What is the consequence of venereal infection of equine viral arteritis

A

Clinically: no carrier state in mare
Venereal infection
* Abortion
o Infection of uterine blood vessels and myometrium =
 vasculitis/myometritis + ischemia and chorionic detachment = abortion of uninfected fetus
 infect trophoblast, chorionic mesenchymal = infected fetus aborted
* Congenital infection if mare infected when late term
o Interstitial pneumonia in newborn

25
Q

What is the consequence of resp infection of equine viral arteritis

A

Resp Infection
* Fever/anorexia
* Leukopenia
* Depression
* Lymphopenia
* Nasal discharge
* Edema (limbs)
o Periorbital edema/conjunctivitis
o Scrotal preputial edema
o Mammary glands
* Epiphora (excessive tears)
* Urticarial rash

26
Q

What is the consequence of equine viral arteritis in stallions

A
  • Stallion: reduced fertility/sperm quality/libido
27
Q

What are the histologic signs of equine viral arteritis

A

Histo: perivascular edema, necrosis of artery wall, lymphocytic infiltration
* Intracytoplasmic inclusions

28
Q

What are the gross lesions of equine viral arteritis in acute infections/foal/aborting mares

A

Gross Lesions
* Acute: edema, congestion, hemorrhage
* Foal: pulmonary edema, interstitial pneumonia, splenic infarct, enteritis
* Aborting mare: endometrial hemorrhage +/- autolyzed fetus

29
Q

How to diagnose equine viral arteritis

A

Dx: Virus isolation (semen + rabbit kidney cells)
* RT-PCR (to detect nucleic acids)
* IHC (to detect antigens)
* ELISA/Virus neutralization for serology
* Can detect carrier stallions by breeding 2 sero(-) mares

30
Q

How to control equine viral arteritis

A

Control: annually notifiable to CFIA
* Separate pregnant mares from others and isolate new animals
* Breed carrier stallions to vaccinated or sero(+) mares
* Isolate infected stallions
* Clean/disinfect
* Can’t eliminate chronic infection
* Vaccine: protect uninfected stallion
o Must vaccinate before breeding season
o Modified live

31
Q

What is the viral features of equine sarcoids

A

Papillomavirus: dsDNA, non-enveloped
Agent: Bovine papilloma virus 1 and 2: Virus infects the basal epithelial cells and eventually released in cornified cells
* Replicate in nucleus
* Does not complete replication in equines – no full viral particle formation
o No amplification of virus in horses/donkey/zebra/mule

32
Q

What is the prevalence of equine sarcoids

A

Prevalence: 20% all equine neoplasia, 36% all skin tumors of horse

33
Q

How are equine sarcoids transmitted

A

Transmit: fomites contaminated by cattle
* Cannot transmit between equids because it does not complete viral replication in equids

34
Q

What are the clinical signs of equine sarcoids

A

Clinically: nodular and verrucous form
* Groin/sheath/face
* Fibroblastic form: leg/groin/eyelid (previous site of injury) – large ulcerated masses

35
Q

What is the pathogenesis of equine sarcoids

A

Pathogenesis: infection and transformation of basal epithelial cells
* Invade dermis

36
Q

What is the histo features of equine sarcoids

A

Histo: long rete pegs into the dermal fibroblastic tissue
* Whorled fibrocellular mass (immature fibroblasts + miotic figures0

37
Q

How to treat equine sarcoids

A

Tx; none
* +/-cryotherapy/excision/immune modulation

38
Q

You are a veterinarian in an equine practice in North
America and presented with horses for vaccination
against equine influenza. The subtype you choose for
vaccination is
A H7N7
B H6N1
C H5N1
D H4N6
E H3N8

A

e

39
Q

The cold-adapted equine influenza vaccines are
considered safe since
A The vaccine strain is temperature-insensitive
B Vaccine strain replicates only in the lower respiratory
tract
C Vaccine strain does not replicate in the host
D Vaccine strain replicates only in the upper respiratory
mucosa
E It is more efficacious when administered during the
winter

A

d

40
Q

Equine Arteritis Virus (EAV) infection
A Is rarely recorded in North America
B Carrier state is common in mares, geldings and foals
C Is not transmitted via artificial insemination
D Reduces fertility in stallion
E Acquired mainly via vector borne transmission

A

D

41
Q

Equine Arteritis Virus (EAV) is transmitted
predominantly via
A Biting flies
B Respiratory route
C Venereal route
D Faecal oral route
E Formites

A

C

42
Q

Equine sarcoids:
A Transmissible between horses
B Occur due to autonomous growth of vascular
endothelium in the skin
C Associated with the presence of bovine retroviruses
D Can be controlled by vaccination
E Cannot be cured

A

E

43
Q

Which virus is the most stable in the
environment?
A Equine influenza virus
B Equine arteritis virus
C Bovine papilloma virus
D Equine herpesvirus
E Poxvirus

A

C

VETM 422 Virology (16 decks)

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