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VETM 422: Virology > avian viral diseases 1 - Aimee > Flashcards

avian viral diseases 1 - Aimee Flashcards

1
Q

Marek’s disease is caused by what kind of virus?

A

Herpesvirus

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2
Q

Describe the pathogenesis of Marek’s Disease.

A
  • Virus enters through respiratory tract then enters macrophages in the lungs = spread
  • The virus curculates to secondary lymphoid organs then spreads through the lymphatic system (early cytolytic infection)
  • The infectious form of the virus is produced in feather follicle epithelium & released in dandruff
  • Late cytolytic infection causes visceral and neural lymphomas
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3
Q

Where does Marek’s disease develop latency?

A

CD4+ t cells

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4
Q

How is Marek’s disease transmitted?

A

Through the respiratory tract

Infectious form of the virus is produced in feather follicle epithelium and released in the feather dandruff

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5
Q

What effect does Marek’s disease have on lymphoid organs?

A

Causes atrophy of spleen, bursa of fabriculus, and thymus = immunosuppression.

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6
Q

What are the clinical signs of Marek’s disease?

A
  • Neurologic signs (paralysis, tics, torticollis)
  • Swollen feather follicles
  • Irregular pupil
  • Increased disease susceptibility
  • Red leg
  • Death
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7
Q

What lesions can be seen with Marek’s disease?

A
  • Swollen sciatic nerve with discoloration and loss of striations (usually unilateral)
  • Pale raised areas on liver due to lymphoid infiltration
  • Lymphoid infiltration in muscle, kidneys, heart and lung, etc (most visceral organs)
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8
Q

What histological changes can be seen with Marek’s disease?

A

Lymphoid proliferation with heterogenous cells (different sizes)

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9
Q

How is latency with Marek’s disease different from other herpesviruses?

A

There is continuous replication in feather follicle epithelium (even when latent)

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10
Q

Describe the immune response to Marek’s disease.

A

Short strong innate response, adaptive starts approx 5 days post infection

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11
Q

What is the only way that a Marek’s disease diagnosis can be confirmed?

A

Need to demonstrate presence of viral genome or antigens to confirm diagosis.

History and exam can lead to suspect MD.

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12
Q

What is the main differential for Marek’s disease?

A

Avian leukosis tumors

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13
Q

How can you distinguish Marek’s disease from Avian Leukosis?

A

Marek’s disease has neurological signs but avian leukosis does not.

Marek’s disease is in younger birds.

Avian Leukosis can be transmitted vertically.

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14
Q

How is MD controlled?

A

Vaccination can reduce MD related losses but not infection.

Vaccination against non-pathogenic forms can create cross protection against MDV1. Or can use attenuated MD1 vaccines.

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15
Q

How did Marek’s disease develop virulence?

A

Vaccination induced jumps in virulence as the virus adapted against vaccine immunity.

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16
Q

What are the advantages of in ovo vaccination?

A
  • Labour saving and convenient
  • Shorter window of susceptibility
  • As effective as D1 vaccination if given into the amniotic cavity
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17
Q

What type of virus causes infectious laryngotracheitis?

A

Herpesvirus

18
Q

ILT is endemic in…

A

backyard flocks in Canada.

19
Q

How is ILTV transmitted?

A
  1. Eye drop
  2. Contact
  3. Shared airspace
20
Q

What are the gross lesions associated with ILTV?

A

Blood, mucus, and yellow caseous exudate or a hollow
caseous cast in the trachea.

21
Q

When do lesions for ILTV and avian pox show up on the chorioallantoic membrane?

A

ILTV = 2 days
Avian pox = 6 days

22
Q

How is ILTV controlled?

A

Modified live virus vaccines (two types = TCO tissue culture origin, CEO chicken embryo origin) or recombinant fowlpox/HVT vaccine with ILTV genes

Biosecurity is really important for control!

23
Q

What are the limitations of ILT vaccines?

A

Modified live:
- Vaccine induced reaction
- Estabishment of latency and gaining virulence
- Involved in recombination leading to increased virulence

Recombinant:
- Partial protection

24
Q

The majority of ILT in Alberta backyard flocks is caused by…

A

CEO vaccine revertants

25
Q

Which ILTV vaccine is recommended for backyard flocks in Alberta?

A

TCO - tissue culture origin vaccine

26
Q

How can ILTV be introduced to a flock?

A
  • Other small flock owners
  • Companion animals, wild birds
  • Darkling beetles
  • Contaminated coveralls, boots and equipment
  • Improper dead bird disposal and handling of infected manure
27
Q

Infectious bronchitis (IB) is caused by what kind of virus?

A

Coronavirus

Non-segmented, enveloped, +ssRNA

28
Q

How is IB transmitted?

A

Respiratory droplets or fecal-oral

29
Q

What is the host species for IB?

A

Mainly chickens

30
Q

What system(s) are affected by IB?

A

It is multisystemic!!!

  • Resp
  • GIT
  • Repro
  • Urinary
31
Q

What cells are infected by IB?

A

Macrophages and monocytes = can circulate through blood and lymph

32
Q

How can the IB viral genome be visualized?

A

In situ hybridization

33
Q

What are the main clinical signs of IB?

A
  • Dyspnea
  • Poor egg quality
  • Shell-less egg syndrome
  • False layer syndrome
34
Q

What is the cause of shell-less egg syndrome?

A

IB infection causes the shell gland/uterus to become edematous and leads to eggs being laid without shells

35
Q

What is the cause of false layer syndrome?

A

IB infection in young birds leads to a cystic oviduct (left)

36
Q

What is common with FLS?

A

Egg laying stance and accumulation of egg yolk in the abdominal cavity

37
Q

How is IB diagnosed?

A

Samples from nasal or tracheal tissue, kidney and intestinal swabs, caecal tonsils

Commercial serum antibody ELISA tests used for monitoring

Molecular techniques such as RT-PCR and sequencing differentiate vaccine and field strains

38
Q

How is IBV controlled?

A

Mainly through vaccination - live attenuated (spray/water) and inactivated vaccines available.

39
Q

What are the issues with IBV vaccines?

A
  • Numerous strains, mutations
  • Poor cross immunity across the variants
  • Short lived protection-revaccination
  • Live vaccines can cause mild infection
  • Recombination of vaccine and field strains
40
Q

How is IB vaccination different between broilers and layers?

A

Broilers - Spray vx on day of hatch and day 10-18 of age
Layers - Inactivated vaccine given every 4-6 weeks starting at hatchery until pre lay

VETM 422: Virology (20 decks)

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