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Food animal production > Marek's disease and avian leukosis > Flashcards

Marek's disease and avian leukosis Flashcards

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1
Q

What is marek’s disease?

A

a herpesvirus-induced neoplastic disease of chickens. characterized by infiltration of various nerve trunks/organs by pleomorphic lymphoid cells

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2
Q

Who does marek’s disease occur in? (species)

A

chickens (sometimes quail, rarely turkey, pheasants, jungle fowl).

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3
Q

What age does marek’s disease occur in

A

sexually IMMATURE chickens 2-7 months (>3 weeks)

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4
Q

What are the three serotypes of alpha herpes virus?

A 
serotype 1--ubiquitous, the oncogenic type is serotype 1
serotype 2--common in chickens, nononcogenic
serotype 3 (turkey) is ubiquitous in turkes and nononcogenic
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5
Q

Is there cross-reactivity between the isotypes of alpha herpes virus?

A

yes

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6
Q

What is the epidemiology of mareks?

A

infected chickens shed virus in feather follicle dander, other birds inhale it. Carriers may or may not be sick and shed throughout life.

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7
Q

Does vertical transmission occur in marek’s?

A

no

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8
Q

What are the clinical signs of Marek’s disease?

A
  1. death

2. paralysis

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9
Q

What are the lesions of marek’s disease?

A
  1. gross enlargement/yellowing/loss of cross-striations of peripheral nerves
  2. discoloration of iris (rare)
  3. enlargement of feather follicles
  4. visceral tumors (most common)
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10
Q

What is skin leukosis

A

A lesion of Marek’s disease. enlargement of feather follicles with reddening

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11
Q

What is seen microscopically with Marek’s disease?

A

lymphomas characterized by PLEOMORPHIC LYMPHOCYTES (T and B cells)

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12
Q

How is Marek’s disease diagnosed?

A
  1. history
  2. clinical signs
  3. distribution of lesions
  4. age–2-5mo or after egg production (late mareks)
  5. histopathology
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13
Q

What are ddx for Marek’s?

A
  1. lymphoid leukosis
  2. botulism
  3. deficiency of thiamine
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14
Q

Why is serology and virology not useful for diagnosis of Marek’s disease?

A

the Marek’s disease virus is ubiuitous

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15
Q

How is Marek’s disease controlled

A

Immunization

Minimize early exposure before immunity develops (7-10d). only need to vaccinate once

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16
Q

How long can MD virus survive in the environment?

A

1 month?

17
Q

What is the most common vaccine for Marek’s disease?

A

serotype 3 (turkey herpes virus) or serotype 2 and 3

18
Q

What is avian leukosis?

A

retrovirus-caused neoplastic diseases of chickens with lymphoid leukosis being most common

19
Q

What are the characteristics of lymphoid leukosis in a flock?

A
  1. persistent low mortality

2. neoplasia of bursa of fabricius with metastasis

20
Q

avian leukosis J causes what?

A

Primarily causes myeloid leukosis

21
Q

What age of birds does avian leukosis occur in?

A

birds 16 weeks or older

22
Q

Avian leukosis viruses (alpha retroviruses) are classified into what?

A

10 subgroups

23
Q

What subgroup of avian leukosis viruses most commonly causes lymphoid leukosis?

A

A

24
Q

Which subgroup of avian leukosis viruses is endogenous?

A

E

25
Q

Does vertical transmission (egg transmission) occur with avian leukosis virus?

A

yes! important mechanism of spread

26
Q

What is the epidemiology of avian leukosis virus

A

vertical transmission. infected chicks are permanently viremic, don’t develop antibody and have increased risk of death from lymphoid leukemia, have fewer eggs (maybe) and likely shed virus to own eggs

27
Q

What are clinical signs of birds with lymphoid leukosis?

A
  1. non specific or no signs
  2. unthrifty or emaciated, pale combs and wattles
  3. enlargement of liver
  4. enlarged and lumpy bursa of fabricius
  5. birds with skeletal myelocyomatosis may have observable masses on shanks, head, thorax
  6. depressed egg production in affected flocks
28
Q

What are the lesions of avian leukosis?

A

lymphomas seen in many organs in chickens >16 weeks esp liver, kidney, ovary, bursa

29
Q

What are the microsopic characteristics of avian leukosis lesions?

A

UNIFORMLY LYMPHOBLASTIC neoplastic cells in lymphoid tumors. Originate from B cells?

30
Q

How is lymphoid leukosis diagnosed?

A
  1. age
  2. course of disease
  3. pattern of mortality
  4. location of gross lesions–bursa of Fabricius nearly always involved
31
Q

Why is virology and serology not that helpful for diagnosing avian leukosis?

A

because ALV is very widespread in chickens

32
Q

How is lymphoid leukosis controlled?

A

by eradication, focused at the level of primary breeding companies–test prior to egg production and remove.

33
Q

Is there a vaccine for avian leukosis? what is it used for?

A

yes, the vaccine is used to immunize parent stock where ALV has been eradicated and they pass their maternal immunity to progeny. Does NOT work for tumor mortality protection as congenitally infected chicks are immunologically tolerant and cannot be immunized.

34
Q

What is the treatment for lymphoid leukosis?

A

none

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