Poultry Flash - Marek's Disease

Question 1

what is the classic case presentation of a bird with marek’s disease?

Answer 1

down, paralyzed chicken with one leg forward

Question 2

what birds are commonly affected by marek’s disease?

Answer 2

chickens 2-5 months old, & turkeys raised near chickens

Question 3

what clinical signs are seen with marek’s disease?

Answer 3

transient paralysis syndrome, depression, distorted iris shape, torticollis, enlarged feather follicles, decreased growth rate & egg production

Question 4

what is seen on necropsy on a bird with marek’s disease?

Answer 4

enlarged peripheral nerves

lymphoid tumors - lungs, heart, liver, spleen, kidney, muscle, gonads, proventriculus, intestines

skin leukosis - enlarged feather follicles

ocular lesions

Question 5

how is marek’s disease diagnosed?

Answer 5

necropsy

histopath & immunohistochemistry, PCR - marek’s viral DNA within lymphomas

Question 6

how is marek’s disease prevented?

Answer 6

vaccination at hatching or in ovo day 18, incubation, & pathogen free flock

Question 7

what is the etiology of marek’s disease?

Answer 7

oncogenic lymphotrophic alphaherpesvirus - highly contagious & ubiquitous in the environment

Question 8

what is the issue with chronic carriers of marek’s disease?

Answer 8

infected chicken carriers (latent or t-cell) will shed virus for a long time through their dander, feathers, desquamated skin, secretions, & droppings

virus persists in litter & dust for months

Question 9

how do you reduce shedding of marek’s disease in chronic carriers?

Answer 9

reduced by prior vaccination!!!

Question 10

what are the 4 common manifestations of marek’s disease?

Answer 10

1. neurologic - paralysis, extending legs, dropping wings
2. ocular - blindness, distorted iris shape
3. cutaneous - enlarged feather follicles & leg lesions
4. visceral - diffuse visceral lymphoid tumors