Marek's Disease

Small and Backyard Flocks May 05, 2015 Print Friendly and PDF

Written by: Dr. Jacquie Jacob, University of Kentucky

Marek's disease, also referred to as visceral leukosis, fowl paralysis, and range paralysis, is caused by a virus. Although there have been reports of infections in pheasants, quail, game fowl, and turkeys, the virus most commonly affects chickens between the ages of 12 to 25 weeks. (Note that although Marek's disease is very similar to lymphoid leukosis, lymphoid leukosis typically starts at 16 weeks of age.) This disease Is spread through the inhalation of feather dander contaminated with the virus. The virus may also be spread by excretions from infected chickens.

Marek's disease is a type of avian cancer. Tumors in nerves cause lameness and paralysis. Tumors can occur in the eyes and cause irregularly shaped pupils and blindness. Tumors of the liver, kidney, spleen, gonads, pancreas, proventriculus, lungs, muscles, and skin cause incoordination, unthriftiness, paleness, weak labored breathing, and enlarged feather follicles. In the later stages of an infection, birds become emaciated and have pale, scaly combs and greenish diarrhea.

Clinical Signs

Clinical signs of Marek's disease include the following:

  • Inability to use or raise the wings
  • Partial paralysis
  • Blindness
  • Ataxia (lack of muscle control)
  • Emaciation

Treatments

There are currently no treatments for Marek's disease.

Prevention and Control

Vaccinations are usually available in hatcheries. All newly hatched birds should be vaccinated for Marek's disease. Following a good biosecurity program helps reduce the likelhood that a flock will become infected.


For More Information

Marek's disease. Tina Savage, University of New Hampshire, and Michael Darre, University of Connecticut.

 

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USDA / NIFA

This work is supported by the USDA National Institute of Food and Agriculture, New Technologies for Ag Extension project.