POULTRY FARMING

Marek’s Disease

Team Pashudhan Praharee

October 16, 2022

769

Marek’s Disease

(MD, Neurolymphomatosis,Fowl Paralysis)

Dr.Shilpa Gajbhiye, Assistant Professor, College of Veterinary Science & A.H. Rewa(M.P.)

Email-drshilpagajbhiye@gmail.com

Keywords- Viral disease, poultry, transmission, MD, age, vaccine, infection, paralysis, tumors, hygiene.

Marek’s disease is a very common disease among chickens. It is caused by herpes virus.MD affects both commercial and backyard poultry and may result in death and sometimes huge production loss. This disease leads to tumors in major internal organs and changes in many of the nerves.

Etiology

Marek’s disease is caused by a herpes virus.

Spread

Infected premises, where day-old chicks will become infected by the oral and respiratory routes.
Young chicks are particularly susceptible to horizontal transmission.
Susceptibility decreases rapidly after the first few days of age.
Dander from feather follicles of infected chickens can remain infectious for more than a year.

Species Affected

The domestic fowl.

Clinical Signs

Weight loss in infected birds and exhibit some form of paralysis.
Mortality may varies from 5 to 50% in unvaccinated birds.
The classical form (paralysis) with leg nerve involvement causes a bird to lie on its side with one leg stretched forward and the other backward.
When the gizzard nerve is involved, the birds will have a very small gizzard and intestines and will waste away.
Mortality usually occurs between 10 and 20 weeks of age.

Diagnosis

The presence of tumours in liver, spleen, kidneys, lungs, ovary, muscles, or other tissues is indicative of MD, but they can also be indicative of lymphoid leucosis.
However, nerve involvement, either grossly (swelling of leg, wing or other nerves) or microscopically, is typical of MD.
Eye involvement can be visible as an irregular constriction of the iris (ocular lymphomatosis).
Skin involvement (skin leucosis) often consists of tumours of feather follicles or in between follicles.
Skin leucosis is a reason for broiler condemnation in certain parts of the world.

Treatment and Control

Vaccination of day-old chicks is an effective mean of control.
MD vaccine only prevents the appearance of Marek’s disease tumours and paralysis, it does not prevent the birds from becoming infected with MD -virus.
It is therefore of major importance to maintain high hygienic and sanitary measures by good management to avoid early exposure of young chickens.

Prevention

The occurrence of Marek’s disease can be successfully prevented by following points:

Preventing the entry of pathogen

Chicks get infected in an environment which is contaminated with MDV, Cleaning and disinfecting can decontaminate the chicken houses. The entry and spread of virus in farms can be effectively and continuously prevented by appropriate architectural measures. This method is used by the producers of specific pathogen free (S.P.F) hatching eggs. SPF flocks are kept in positive pressurized houses having filters to nullify possibility of entry of any microorganisms.

Following vaccination protocol

Proper application of the vaccine – dilution mistakes during the preparation, faults in the technique of injection, too long times of storage or too high ambient temperate of reconstituted vaccines.

Proper dosing of vaccine– The protection by inoculation depends on the dose of injected viruses.

Cleanliness and hygiene after vaccination– An infection with virulent MDV occurs simultaneously with or a few days after the vaccination. So accurate cleaning/ disinfection and strict biosecurity measures, for first 15 days post hatchery vaccination.

Sterlization -Contamination of a vaccine can lead to damage to the inoculated chick by concurrently present microorganisms. Accurate sterilization of injection appliances before being used.