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VETM 422 Virology > Lecture 17: Avian Viruses > Flashcards

Lecture 17: Avian Viruses Flashcards

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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?

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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

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A

Herpesviridae > alphaherpesvirus > itovirus

20
Q

What is the species of virus causing Infectious laryngotracheitis

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A

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

21
Q

What is the pathogenesis of Infectious laryngotracheitis

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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

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

What are the gross signs of Infectious laryngotracheitis

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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

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A

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

25
How is Infectious laryngotracheitis diagnosed? What other virus can also be diagnosed this way?
* 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
What are the types of vaccines are available for Infectious laryngotracheitis? What should you reccomend
* 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
What are the limitations of vaccines available for Infectious laryngotracheitis?
* 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
What are other (non-vaccine) control mechanisms for Infectious laryngotracheitis
* Mainly controlled by biosecurity * Reportable disease * Biosecurity o Depopulation recommended when found in backyard flocks  In Alberta vaccination (not depopulation) is recommended
29
How is Infectious laryngotracheitis transmitted to backyard flocks
o Other small flock owners o Companion animals/wild birds o Darkling beetles o Contaminated coveralls/boots/equipment o Improper handling of dead birds/manure
30
What is the taxonomy of infectious bronchitis
Coronaviridae > coronavirus > gammacoronavirus
31
What type of virus causes infectious bronchitis
Type * Non-segmented genome * +ssRNA – enveloped * Very large
32
How does infectious bronchitis transmit and what species are affected
Transmit: respiratory and fecal oral Target: chickens (mainly)
33
What is the pathogenesis of infectious bronchitis
* 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
What are the clinical signs of infectious bronchitis
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
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
D
36
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
C
37
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
E
38
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
B
39
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
C
40
What are the gross lesions associated with infectious bronchitis
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
How is infectious bronchitis diagnosed
* sample: nasal/tracheal/kidney/interstitial/caecal tonsl swab * stunting and curling of embryo (9-11d) * ELISSA * RRT PCT
42
How is infectious bronchitis controlled
* 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
How does infectious bronchitis control compare between layers and broilers
* 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 (19 decks)

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