From time to time we see a chicken keeper post here who has received a diagnosis in their flock of lymphoid leucosis. This disease is terribly common in American chicken flocks, about as common as Marek's. Getting this diagnosis is usually met with panic since you usually get this scary news only after a chicken has become sick and died. That certainly was my first reaction when it was diagnosed in my flock. The second reaction was, "this is the end of my flock and the end of my world".
That was around seventeen years ago. Since then, I've learned to live with this disease and to manage my flock in specific ways to deal with it. It has not been the end of the world. In fact, it's been years since there has been any active symptoms in my flock except for my current rooster. There are some definite do's and don'ts, and if you follow the rules, a leucosis flock can be nearly as normal as any other flock.
While Marek's and lymphoid leucosis both can cause cancerous tumors, they are caused by different viruses. Marek's is caused by the herpes virus while leucosis is caused by a retro virus. https://www.merckvetmanual.com/poul...eukosis-in-poultry#Clinical-Findings_v3342481 If you like scientific reading, this is for you. For others, I will tell of my experience and invite questions.
Lymphoid leucosis differs from Marek's in time of onset. While Marek's shows up around age eight weeks, leucosis typically shows up around four to five months. Like Marek's, the first symptom often is lameness. From there, the chicken gets sicker, stops eating, loses weight, and dies. If you do a home necropsy on the dead bird, you will likely see a drastically enlarged liver. The chicken I sent to the lab had a two pound liver. Often you'll see hundreds of little white tumors on all the organs.
There is no vaccination for lymphoid leucosis. However, with good management, chickens in a leucosis flock can build up resistance to the disease and lead perfectly normal full lives.
Here are the "rules". Introducing adult chickens into a leucosis flock is a death sentence for those new chickens. However, you can safely bring new baby chicks into the flock, and during those first few weeks, they can begin to form antibodies against the disease if you brood them in proximity to the flock. This process will continue, and most of these chicks may never become symptomatic. However, I lost an entire group of new chicks to the disease when a symptomatic hen decided to brood the chicks at six weeks of age. I didn't understand it at the time, but they were being exposed to the full force of the disease by sleeping under her. It was a very painful lesson.
Another painful lesson I learned was not to try to hatch chicks from my flock. The disease is passed into the egg by a hen with lymphoid leucosis so those chicks are hatched with the disease. (The eggs are safe to consume by humans, though.) These chicks rarely make it beyond one year. I only had two chickens hatched from my flock make it beyond that, and each did become symptomatic eventually. Currently, one of those chicks is still alive at age ten years, but he has cancer in his leg.
No chickens must be rehomed from a leucosis flock. No hatching eggs must leave the flock. You must not wear the same footwear you use in your run to run errands or risk spreading the disease on the floors of stores where others can bring the disease home to their flocks.
A good balanced diet and keeping the premises as free of feces as possible all help to boost immune systems to keep the chickens asymptomatic. With all these measures, a leucosis flock can be as healthy as any other and live just as long, if not longer. My oldest chicken was nearly fourteen when she died.
There is another big difference between Marek's and leucosis. If you do wish to cull an infected flock, the disease is easily eradicated from the premises with a disinfectant. You can start a new flock almost immediately. With Marek's, the virus will last for a year or longer in the soil and is not easily removed with disinfectants. It's much, much easier to deal with lymphoid leucosis than Marek's.
That was around seventeen years ago. Since then, I've learned to live with this disease and to manage my flock in specific ways to deal with it. It has not been the end of the world. In fact, it's been years since there has been any active symptoms in my flock except for my current rooster. There are some definite do's and don'ts, and if you follow the rules, a leucosis flock can be nearly as normal as any other flock.
While Marek's and lymphoid leucosis both can cause cancerous tumors, they are caused by different viruses. Marek's is caused by the herpes virus while leucosis is caused by a retro virus. https://www.merckvetmanual.com/poul...eukosis-in-poultry#Clinical-Findings_v3342481 If you like scientific reading, this is for you. For others, I will tell of my experience and invite questions.
Lymphoid leucosis differs from Marek's in time of onset. While Marek's shows up around age eight weeks, leucosis typically shows up around four to five months. Like Marek's, the first symptom often is lameness. From there, the chicken gets sicker, stops eating, loses weight, and dies. If you do a home necropsy on the dead bird, you will likely see a drastically enlarged liver. The chicken I sent to the lab had a two pound liver. Often you'll see hundreds of little white tumors on all the organs.
There is no vaccination for lymphoid leucosis. However, with good management, chickens in a leucosis flock can build up resistance to the disease and lead perfectly normal full lives.
Here are the "rules". Introducing adult chickens into a leucosis flock is a death sentence for those new chickens. However, you can safely bring new baby chicks into the flock, and during those first few weeks, they can begin to form antibodies against the disease if you brood them in proximity to the flock. This process will continue, and most of these chicks may never become symptomatic. However, I lost an entire group of new chicks to the disease when a symptomatic hen decided to brood the chicks at six weeks of age. I didn't understand it at the time, but they were being exposed to the full force of the disease by sleeping under her. It was a very painful lesson.
Another painful lesson I learned was not to try to hatch chicks from my flock. The disease is passed into the egg by a hen with lymphoid leucosis so those chicks are hatched with the disease. (The eggs are safe to consume by humans, though.) These chicks rarely make it beyond one year. I only had two chickens hatched from my flock make it beyond that, and each did become symptomatic eventually. Currently, one of those chicks is still alive at age ten years, but he has cancer in his leg.
No chickens must be rehomed from a leucosis flock. No hatching eggs must leave the flock. You must not wear the same footwear you use in your run to run errands or risk spreading the disease on the floors of stores where others can bring the disease home to their flocks.
A good balanced diet and keeping the premises as free of feces as possible all help to boost immune systems to keep the chickens asymptomatic. With all these measures, a leucosis flock can be as healthy as any other and live just as long, if not longer. My oldest chicken was nearly fourteen when she died.
There is another big difference between Marek's and leucosis. If you do wish to cull an infected flock, the disease is easily eradicated from the premises with a disinfectant. You can start a new flock almost immediately. With Marek's, the virus will last for a year or longer in the soil and is not easily removed with disinfectants. It's much, much easier to deal with lymphoid leucosis than Marek's.
