Marek`s disease: Tumors in poultry
Published: November 17, 2015
By: Abdelaziz Abdelfatah
it is one of aneoplastic viral disease primarly affect chicken and rarely affect turkey and firstly detection of the virus occur at year of 1980 by ( dr jozef Marek) and the virus is belongs to Herpes virus of DNA viruses this viruses characheterized by the infiltration of neoplastic cells of cells forming lymphocyt in many organs as nerves trank and internal organs and most of the virus type are antigenically related to each other and greatly differs according to their onchogonisty and ability to form tumors and some of serotypes are highly virulant and other are avirulant the female chicken is mostly affected than male one.
Some characters related to the virus .
Mode of transmission.
by horizontal transmission only and the infection occur through the respiratory tract of poultry by the inhalation of the virus which founded on the epithelial tissue of feather or skine dander and so it is very important from our field experience to burn the collected feather of birds at time of 80 days old when the feather renewed and prevent the ability of transmission of this virus infection and also burn the feather collected every 3 days during egg production. also the virus can infect birds through the digestive tract by ingestion the contaminated food and water which affected by the secrection of affected birds.
the virus of markes shedes after 6 weeks age from infection and can make post mortum lesion and signs at day after 80 days old.
Types and serotypes of markes disease.
- serotype 1.
oncogenic strain like .GA. MD11. MD5. TK. RBIB low pathogenic strains as CV1988(RESPINES).
- serotype 2.
SBI.
- Serotype 3.
HVT.
Infection with markes disease doesnt mean that the birds will develop tumor as it depends on factors belongs to the virus itself.
- dose of the virus inhalled by bird
- virulance of virus during infection
- onchogencity
Factors belong to bird itself.
- genetic of bird
- age of bird and if the infection occur early through 2 weeks after hatch or not
- sex of bird
- immunization
Factor belongs to the environment.
like hygenic measures and stressfull factors and all in all out of the flock reared in the farm.
Clinical signs of Markes disease viruses.
first wave of the virus infection occur to bursa and thymus gland destroying the mucosal immune system of bird. The virus replicate to fully infection form in the feather follicules. The tumor occur from the virus by malignant transformation of the lymphocyte in diferent tissues.
the general clinical signs of markes is.
the bird affected is dull and emaciated of pale comb and wattle and the feed and water intake is decresed.
in some cases appearance of lamness and dulleness and most of signs is differs according to the organs affected as .
Eye lesion.
Irregularity eye pubile. and like fish eye and mostly be unilateral and if bilateral the bird will be blind anular depigmention in iris which appearanc as grayish spot loss of intenisty to light
Neural form.
If vagus nerve affected the paralysis occur and respiratory manifestion occur and appearance of tumors on lung tissue like if nerves of digestive tract affected so paralysis occur and appearance of flaccid crop appearance and dirrhaee and some tumors which take whitich colouration on the mesentery like.
If sciatic nerve affected and loss his striation and the bird take the posture of pallourina posture and this must differantianted from vit B defieciancy from our experiance especially the loss of stratian of sciatic nerve as.
Visearal form.
Occur as scatered of tumor in different parts of birds as heart and spleen and proventriculus and liver which is very enelarged and kidney which occur in rare form as.
Gonadal form.
which occur to ovary destroying the ovary and make infertility.
Cutanous form.
which occur to feather follicles and leads to defeathering of skine and scatered of alot of it on letter in farm ground.
Mortility can be extended for about 40 weeks and the virus can live in normal atmospher for about 65 weeks and the birds will be viramic for extended life and the virus itself is very difucult in its control by sanition as it resistant to phenol and quantery ammonium cloride.
Clinical diagnosis of Markes disease in brief.
- by clinicopathological examination
- by histopathological examination and presence of intranuclear inclusion bodies
- by isolation and identification of the virus by agar gell ppt and using of floresent antibody tech(FAT)
- by differantial diagnosis .
- it should differantiated from some disease make tumors like.
- lymphoid leuckosis as
Control of Markes.
- genetically by genetic selection of breeds which are more resistant.
- environmental factor.... by puting bird in good hygenic condition beyond the stress and make good veterinary hygienic measures and removal of skine collected every 3 days especially after 80 days old chick and burn it make good hygenic measure to the flock.
- by vaccination.
- there is some facts:
About vaccination which repesented in markes vaccination take 10 days for immunity to birds.
Markes disease interfer with the immunity to coccidosis.
Live vaccine of reovirus can potenially interfer with the response to MARKES DISEASE VACCINATION IF THEY USED after each other directly adminstration o fowl pox vaccination at one day old with the markes vaccination is good and preferable and can give immunostimulation status to bird
There is 3 types of vaccination.
- serotype one.......is virulant strain vaccine which is attenuated and called Respines strain vaccine.
- serotype two.....is avirulant vaccine of Turkey Herpes vaccine(H.V.T).
- third serotype is...... chicken strain which is avirulant fowl strain.
From our field experience we prefer to use the bivalent vaccine of the Respines and H.V.T vaccine as one vaccine at one day old chick under skine of neck or I.M injection in the end of my brief post about markes disease which i go far from the scientific complication about markes and mix between my field experience and the acadimic situation which is written from my books(poultry disease and hygene for future poultry consultant part 1. 2 .3) most of postmortuim photo is belong to me and occur from my field situation thanks for all.
References.
1. field observation of dr abdelaziz.
2. poultry disease and hygene for future poultry consuldant...editor of dr abdelaziz abdelfatah.
3.poultry international magzines.
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