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VETM 422 Virology > Lecture 17: Avian Viruses > Flashcards

Lecture 17: Avian Viruses Flashcards

1
Q

What is the taxonomy of mareks dz

A

Herpesviridae > alpha herpes virus > mardivirus

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2
Q

How are the types of mareks disease named

A

Terminology
* MDV serotype 1 (gallid herpesvirus 2)
* MDV serotype 2 (gallid herpesvirus 3)
* Herpesvirus of turkeys (melagrid herpesvirrus 1)

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3
Q

What is the pathogenesis of mareks disease

A
  • Induce lymphoma: infect CD4 T cells causing visceral and neural lymphoma
  • Infectious virus only found in follicular feather epithelium
  • Viral replication in lungs – affect alveolar macrophages and immune cells
    o Can circulate and transport to lymphoid organs (spleen/thymus/bursa of Fabricius)
    o Infect T cells in lymphoid organs
  • Become latent in CD4 T cells
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4
Q

How is Mareks disease transmitted

A

Transmit: respiratory

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5
Q

What are the clinical signs of mareks disease

A
  • Chronic polyneuritis – sciatic nerve swelling (usually unilateral)
  • Visceral lymphoma (liver/proventriculus/ventriculus/spleen/kidney/heart/lung..)
  • Immunosuppression
  • Transient paralysis/torticollis – neck paralysis
  • Acute brain edema
  • Acute rash
  • Swollen feather follicles
  • Tumor cell infiltration in wattle/cornea/pupil/skin tumors
  • Increased disease susceptibility
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6
Q

What are the pathotypes of mareks disease

A

Pathotypes
* Mild
* Virulent
* Very virulent
* Very virulent + = severe immunosuppression
* Increasing bursal and thymic atrophy (not a big effect on the spleen)

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7
Q

What are the histo features of mareks dz

A
  • Lymphoid proliferation in muscle, heart, and skin
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8
Q

What is the main other differential for mareks disease

A
  • Main ddx is avian leukosis tumors (from a retroviral infection)
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9
Q

Differentiate mareks disease and avian leukosis virus

A

o Mareks dz: >6 weeks (avian leukosis >16 week)
 Neuro signs, usually tumors on proventriculus/skin/muscle, neural enlargement and histo change
* Not seen in avian leukosis
 Bursa of Fabricius: diffusely enlarged in mareks (nodular in avian leukosis)
 T cells (B cells affected in avian leukosis)
 Tumor from lymphoblast and lymphocytes (avian leukosis = only leukoblasst)
 Horizontal transmit (avian leukosis = vertical and horizontal)

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10
Q

How does immunity progress in mareks disease

A
  • Initial lung infection followed by early cytolytic infection then late cytolytic infection
  • Replicate in feather follicular epithelium continuously even while latent in CD4 T cells
  • Initially = innate response – transient (gone within 3d)
  • 5-6d = adaptive immune response initiated
    o Strong immune response
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11
Q

Differentiate mareks and avian leukosis*

A
  • Main ddx is avian leukosis tumors (from a retroviral infection)
    o Mareks dz: >6 weeks (avian leukosis >16 week)
     Neuro signs, usually tumors on proventriculus/skin/muscle, neural enlargement and histo change
  • Not seen in avian leukosis
     Bursa of Fabricius: diffusely enlarged in mareks (nodular in avian leukosis)
     T cells (B cells affected in avian leukosis)
     Tumor from lymphoblast and lymphocytes (avian leukosis = only leucoblast)
     Horizontal transmit (avian leukosis = vertical and horizontal)
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12
Q

What methods are used to diagnose and confirm mareks disease

A
  • Use Hx/PE: paralysis/skin nodules/grey eyes in chickens 6wk or older
  • PM exam: lymphoma in skin/nerve/proventriculus/muscle + diffuse enlargement of bursa of Fabricius
  • Histo: brain inflammation + pleomorphic lymphoid infiltration in skin/muscle/proventriculus/nerves
  • Immunological: identify types of cells (CD4/CD8/IgM mainly)
  • Confirm via immune/viral/molecular evaluation to demonstrate viral mRNA or genome in affected tumors
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13
Q

How is mareks disease controlled? What are the features of the control mechanisms

A
  • Vaccine: administered at hatchery
    o Reduce disease related loss but not infection
    o MeHV-1 (HVT) – serotype 2
    o Ga-HV3 (SB-1) – serotype 3
    o Serotype 2 and 3 are non-pathogenic for chickens = do not need to modify/attenuate the virus in the vaccine
    o GaHV-2 (CVI988/Rispens) – serotype 1 (live attenuated)
     pathogenic and therefore must attenuate/modify the virus for vaccine
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14
Q

What is the relationship between virulence and the control mechanism for mareks disease

A
  • introduction of more efficacious vaccines resulted in increasing virulence of the virus
    o HVT > HVT+SSBI > Rispens = vaccine introduction chronologically (increasing efficacy)
    o Virulent MDV > vvMDV > VV+MDV = associated increases of virulence over time
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15
Q

How does in ovo vaccination work for chickens

A

o At embryo day 18: in ovo vaccine is administered
 Use 2.5cm needle – inject to the hub – inject into amniotic cavity most of the time (1% of the time it will hit the neck of the bird)
 If it is deposited in non allantoic cavity then it isn’t effective

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16
Q

How does chicken egg production work and how does it relate to vaccination

A

o 21d for chicken egg to incubate
o Incubator:
 setter compartment – 1-18d
 hatcher compartment – 18 – 21d
 transfer eggs at 18d = should vaccinate eggs then
o 3 membranes: (outer) chorioallantois > yolk sac > amniotic (inner)

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17
Q

What are 3 main benefits of in ovo vaccination for mareks disease

A

o Reduced window of susceptibility
 In unvaccinated = immunity develops at 7 days
 In vaccinated = immunity develops at 4 days

o Benefits:
reduced window of susceptibility
cost effective, 100% intake

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18
Q

What type of chickens is in ovo vaccination used?

A

o Only used in broilers:

not in layers
- the males are not kept so they don’t want to vaccinate all of them

19
Q

What is the taxonomy of Infectious laryngotracheitis

A

Herpesviridae > alphaherpesvirus > itovirus

20
Q

What is the species of virus causing Infectious laryngotracheitis

A

Types
* Group 1 dsDNA
* Species: gallid herpesvirus 1 (GaHV1)

21
Q

What is the pathogenesis of Infectious laryngotracheitis

A

Path: Upper resp infection
* Viral antigens detected in the tracheal epithelium
* Induce syncytia (multinucleated giant cells – merging of neighbouring cells) – dissolve cell membranes
* Epithelial sloughing in respiratory – expose underlying blood vessels

22
Q

What are the histo signs of Infectious laryngotracheitis

A
  • Form syncytial cells in the trachea and conjunctive
23
Q

What are the gross signs of Infectious laryngotracheitis

A

Gross
* Blood/mucus/ yellow caseous exudate
* Over time becomes a hollow caseous cast in trachea

24
Q

What are the clinical signs of Infectious laryngotracheitis

A

Clinically
* Dyspnea, coughing
* Coughing up bloody mucus is characteristic
* Conjunctivitis

25
Q

How is Infectious laryngotracheitis diagnosed? What other virus can also be diagnosed this way?

A
  • Embryonated eggs between 9-12d
    o Make hole in cell and put virus into chorioallantois membrane
     If it is ILT – within 2 days you will see pock lesion (if in 6 days then it is avian pox)
  • Both avian pox and ILT can be diagnosed this way
26
Q

What are the types of vaccines are available for Infectious laryngotracheitis? What should you reccomend

A
  • Vaccine – eyedrop
    o Modified live
    o No inactivated
    o Do not use the CEO vaccines – will increase virulence over time
  • Types of vaccine:
    o TCO-tissue culture origin
    o CEO- chicken embryo origin
    o Recombinant fowlpox/HVT vaccine with ILTV genes = partial protection (administered in ovo or 1d)
27
Q

What are the limitations of vaccines available for Infectious laryngotracheitis?

A
  • Limitation
    o Vaccine reaction
    o Establishment of latency and increasing virulence
    o Transmission of vaccine virus between birds and flocks increases virulence
    o Involved in recombination leading to increased virulence
28
Q

What are other (non-vaccine) control mechanisms for Infectious laryngotracheitis

A
  • Mainly controlled by biosecurity
  • Reportable disease
  • Biosecurity
    o Depopulation recommended when found in backyard flocks
     In Alberta vaccination (not depopulation) is recommended
29
Q

How is Infectious laryngotracheitis transmitted to backyard flocks

A

Infectious laryngotracheitis

30
Q

What is the taxonomy of infectious bronchitis

A

Coronaviridae > coronavirus > gammacoronavirus

31
Q

What type of virus causes infectious bronchitis

A

Type
* Non-segmented genome
* +ssRNA – enveloped
* Very large

32
Q

How does infectious bronchitis transmit and what species are affected

A

Transmit: respiratory and fecal oral
Target: chickens (mainly)

33
Q

What is the pathogenesis of infectious bronchitis

A
  • Inhaled and goes to respiratory tract
  • Causes viremia and can infect macrophages
  • Impact GI/repro/cecal tonsils/urinary tract (kidneys)
  • Causing reduced egg production/cystic oviduct/shell gland edema/male infertility/nephritis
    o ovary/oviduct pathology – infect/affect isthmus and uterus of oviduct
  • Viral replication in the trachea and kidney
34
Q

What are the clinical signs of infectious bronchitis

A

Clinically:
* production birds and young – dyspnea
* watery albumin
* brown eggs will be discoloured (become lighter)
* wrinkled/soft shell/shell-less eggs (due to inflammation)

o penguin stance: look like they are going to lay an egg (from false layer)

35
Q

Which of the following statement about in ovo vaccination
against Marek’s disease (MD) is TRUE?
a Vaccination usually takes place seven days before hatch
b Vaccine is inoculated into the yolk sac
c In ovo vaccination is not as effective as post-hatch vaccination
d Vaccine is inoculated into the amniotic cavity
e Vaccine is inoculated onto the chorioallantoic membrane

A

D

36
Q

Marek’s disease (MD) is different from avian leukosis since:
a The MD is caused by a retrovirus but avian leukosis is caused by a
herpesvirus
b MD is characterized by visceral tumors and avian leukosis is
characterized by lymphoid depletion
c MD but not the avian leukosis is characterized by neurological
signs
d Causative viruses of both MD and avian leukosis are transmitted
vertically
e Both MD and avian leukosis are commonly seen in 1-7 days old
chickens

A

C

37
Q

Infectious laryngotracheitis virus (ILTV) infection:
a Leads to anemia and diarrhea in addition to respiratory signs
b Is endemic in commercial flocks in Canada and rest of north
America
c Is an acute infection and the causative virus is cleared in 7-10
days post-infection
d The causative virus belongs to the Family, Retroviridae
e Is characterized by dyspnea and blood-tinged respiratory mucus

A

E

38
Q

What is NOT true about Infectious bronchitis virus (IBV)
infection:
a Causes egg production drops and poor egg quality
b Is endemic in commercial flocks in Canada
c Vaccines are not available for the control
d The causative virus belongs to the Family, Coronaviridae
e The clinical signs include respiratory clinical manifestations

A

B

39
Q

False layer syndrome (FLS):
a Leads to poor egg quality
b Is considered a foreign animal disease in Canada
c Is associated with development of cystic oviduct lesions
d The causative virus belongs to the Family, Herpesviridae
e Affected birds suffer from respiratory clinical signs

A

C

40
Q

What are the gross lesions associated with infectious bronchitis

A

Gross
* false layer syndrome: left oviduct becomes cystic due to virus infection within first 2 weeks of hens life (right cystic oviduct is normal)
o result in accumulation of egg yolks in abdominal cavity (because there is no oviduct but ovaries are still there) = egg yolk peritonitis
o penguin stance: look like they are going to lay an egg
* kidney lesions (nephropathogenic virus forms)

41
Q

How is infectious bronchitis diagnosed

A
  • sample: nasal/tracheal/kidney/interstitial/caecal tonsl swab
  • stunting and curling of embryo (9-11d)
  • ELISSA
  • RRT PCT
42
Q

How is infectious bronchitis controlled

A
  • vaccination will prevent egg production loss (from reduced production and bad quality)
  • live attenuated vaccines: administer via spray or by water
    o but many strains and mutations with poor cross variant immunity
    o short lives protection required multiple revaccination
  • live vaccine can cause mild infections
  • there are recombination of vaccine and field strains
43
Q

How does infectious bronchitis control compare between layers and broilers

A
  • broiler: chicken-coarse spray vaccine on day of hatch and 10-18d
  • layer: vaccine every 4-6wks beginning at hatchery until pre lay (14-16 weeks) – inactivated vaccine

VETM 422 Virology (17 decks)

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