Mareks Disease paralysis
Mareks disease is a Herpes virus infection of chickens and turkeys that live with chickens. The eighties and nineties brought some highly virulent strains to the U.S. and Europe.
Symptoms are neurological problems such as floppy necks, transient paralysis, long standing paralysis of the legs or wings, eye lesions, tumors in the hear, ovaryies, testies, muscles, lungs, and feather follicles. It is highly contagious, between ten and fifty percent of a flock will come down with the virus and mortality reaches one hundred percent. Once it roars through a flock the mortality will continue for nearly three quarters of a year and the weakened bird are susceptible to other bacterial, viral, and parasitical diseases.
Usually spread through respiratory means and also dander from infected feather follicles. The surviving birds remain carriers for life. The virus is quite hardy, surviving outside of a host for over a year and resistant to ammonia and phenol based disinfectants. It easily survives freeing and thawing.
Signs of Mareks disease are paralysis of the legs, wings, and neck, loss of weight, grey or irregular pupils, partial blindness, skin around feather follicles is rough and raised. .Prevention depends upon biosecurity, sanitation and hygiene, all in and all out production where possible, purchasing resistant strains, and vaccination. Once again a good bird proof treadle feeder is a must.
Even when extreme biosecurity is practiced Mareks disease can find its way into your flock. Due to the tenacity of the disease it is a good idea to disinfect after visiting a feed store, not allowing other flock owners to visit your coops, not visiting other coops, and purchasing hatching eggs instead of hatched chicks. Commercial or backyard flocks will spread the disease through wild birds and the disease is so hard to eradicate that farmers once recommended burning the entire chicken house to the ground along with the chickens in it. However keeping a closed flock, vaccinating, and possibly even breeding for resistance to the disease is worth trying.
Vaccinations do not actually stop the transmission of the disease but it does lessen the severity which in turn allows the bird to live to spread the disease. Breeding for resistance would require being hard hearted, not treating birds that contract the disease but culling the birds and burning the carcasses.
. That also means not relying upon disinfectants other than lime to expose the birds to all sorts of bacteria and viruses. Good nutrition, clean and un-crowded coops are a necessity if you attempt this route. Deliberate exposure to disease rather than attempting biosecurity and allow the fittest to survive.
Purebred animals are always less vigorous and less hardy and that extends to disease as well. Deliberately exposing the birds instead of biosecurity, antibiotics, and coddling the flock is the only possible way to breed resistance into the flock. Any surviving birds will be the most resistant to the disease and should be used as the brood stock for future generations.