Marek's Virus questions come up so frequently, I thought I would address the subject in some detail. My information is based on my discussions with professionals, vets & I hope it helps you and other readers.
Probably not Marek's in your case but I cannot be sure because they do not act drunk in classic Marek's -- at first, they are unsteady on their feet, gradually, they lose use of one leg, then the other, all the while, they are alert & otherwise fine, they eat food, drink water . . . gradually over a week or two, they lose the use of both legs and cannot stand and must sit. They will scoot along on their abdomen to get to food and water even using their wings. Gradually, they lose use of their wings and must be put down to prevent starvation.
Another form of Marek's can cause sudden death at any age, another form will cause blindness usually at a later age. I have experienced the classic, the blind form and the sudden death.
The vaccine must take hold. There is a specific age window in a chick's life when they can contract Marek's. Even if vaccinated, before the vaccine takes hold and immunization develops, if the chick comes into contact with the virus via dust, dander, on your clothing, etc., it can still contract the disease so the vaccine is not 100%. For a vaccine to take hold , it takes at least TWO WEEKS (so chicks should have no contact with other birds for 2-3 weeks following vaccination on day one NOR your clothing, shoes etc. from being out in your pens. Marek's is carried by dander, on dust, is long-lived in the environment (50 years or more). Wild birds carry it. THE NORMAL TIME A CHICK IS SUSCEPTIBLE TO CATHING THE VIRUS (UNVACCINATED) -- THE SHORT WINDOW I SPEAK OF, IS HATCHING THROUGH ABOUT 24 WEEKS. This is why vaccinating an older bird is of little use. Some folks (and some research) suggests a booster, later on, to vaccinated birds can be helpful.
Marek's is everywhere, worldwide and everyone should assume their flock is infected. I used to have it. I'd lose a bird or two each season, usually at point of lay for a pullet and between 7-12 months for a male. I chose not to vaccinate (even though I ordered the vaccine in the beginning). I tried having turkeys around and that worked except the turkeys would get blackhead so I got rid of them.
(the vaccine is made from the turkey's herpes virus which is safe for turkeys and chickens alike -- having chicks around turkey poop is similar to vaccinating -- the Turkey herpes virus causes chickens to develop immunity to some forms of Marek's).
Instead, I begin breeding from old stock at least over one year of age & older if I could that appeared healthiest. I have built a resistance in my flock as I have not had a death in a couple of years.
Back in the 1970s, the commercial industry were losing about 1.5% monthly. The vaccines were developed for the commercial industry. The industry vaccinated in the embryo in the egg. Nowadays, the losses in the industry to Marek's have ceased. Some Marek's strains are more virulent than others.
Some infected birds never show any symptoms. If birds are not vaccinated, they may be immune, or they may have been exposed and it show up later -- cannot tell.
The virus may be virulent and many birds in a flock will die over a relatively short time--or a very "weak" virus that infects few birds. You may have only one bird at a time--over a number of years, die after showing the symptoms. Sudden death may indicate Marek's--you must do a necropsy to be sure. It's appearance in a flock is not a death-knell for them all. (Or it can be.)
I confirmed that what I was seeing (as classic Marek's) because I sent a couple of birds to the lab. This is the only way to confirm that it is Marek's.
One more thing: you CANNOT disinfect for Marek's and you CANNOT get rid of it. Marak's is NOT carried in eggs. You CANNOT know if your birds resistant or immune.
Pros of vaccination- some, but not complete, protection against a potentially devastating virus. Peace of mind.
Cons of vaccination- cost, both in time and money, if you do it yourself. But certainly cost is always a factor. If you have a closed flock (no new birds in, breed all your own replacements, no biosecurity breakdown)then it is hard to justify the cost.
A vet who knows about chickens told me:
Quote: ~The reality is that companies that develop vaccines do so with the production market in mind and since vaccination has to occur at day one for the production market, that is where the energy and money have been focused. Those of us who are small time chicken lovers may reap the benefits but are not the focus. Hence, the lack of a marek's vaccine for 12 week old (pick any age) pet chickens on the market. I remember from school that there were flocks in multiple countries that had reported resistance factors to Marek's, as well as, to other diseases. And by default, we must assume there are also susceptibility factors that run in lines, even if it is just the lack of a resistance gene . . .
~The reason chicks must be separated from unvaccinated birds is that the vaccine is not effective until the chicks' immune systems have had a chance to respond. This takes days to weeks (by 3 or a poor immune system is likely to blame). The vaccinated chicks aren't a danger to other birds. It is the other way around. An unvaccinated bird may still transmit the virus to your newly vaccinated chicks. Remember that at its best the vaccine isn't 100% effective in a flock or in an individual bird. Some birds may not be protected at all (prior exposure to disease, poor vaccination husbandry, other current illnesses, ineffective immune systems, etc.); and there are many birds that end up with lesser cases of Marek's because they have been vaccinated but are not fully protected from getting it. The current thought is that the shedding time is shorter in vaccinated birds that do happen to get the virus.
HOPE THIS ALL HELPS!
Probably not Marek's in your case but I cannot be sure because they do not act drunk in classic Marek's -- at first, they are unsteady on their feet, gradually, they lose use of one leg, then the other, all the while, they are alert & otherwise fine, they eat food, drink water . . . gradually over a week or two, they lose the use of both legs and cannot stand and must sit. They will scoot along on their abdomen to get to food and water even using their wings. Gradually, they lose use of their wings and must be put down to prevent starvation.
Another form of Marek's can cause sudden death at any age, another form will cause blindness usually at a later age. I have experienced the classic, the blind form and the sudden death.
The vaccine must take hold. There is a specific age window in a chick's life when they can contract Marek's. Even if vaccinated, before the vaccine takes hold and immunization develops, if the chick comes into contact with the virus via dust, dander, on your clothing, etc., it can still contract the disease so the vaccine is not 100%. For a vaccine to take hold , it takes at least TWO WEEKS (so chicks should have no contact with other birds for 2-3 weeks following vaccination on day one NOR your clothing, shoes etc. from being out in your pens. Marek's is carried by dander, on dust, is long-lived in the environment (50 years or more). Wild birds carry it. THE NORMAL TIME A CHICK IS SUSCEPTIBLE TO CATHING THE VIRUS (UNVACCINATED) -- THE SHORT WINDOW I SPEAK OF, IS HATCHING THROUGH ABOUT 24 WEEKS. This is why vaccinating an older bird is of little use. Some folks (and some research) suggests a booster, later on, to vaccinated birds can be helpful.
Marek's is everywhere, worldwide and everyone should assume their flock is infected. I used to have it. I'd lose a bird or two each season, usually at point of lay for a pullet and between 7-12 months for a male. I chose not to vaccinate (even though I ordered the vaccine in the beginning). I tried having turkeys around and that worked except the turkeys would get blackhead so I got rid of them.
(the vaccine is made from the turkey's herpes virus which is safe for turkeys and chickens alike -- having chicks around turkey poop is similar to vaccinating -- the Turkey herpes virus causes chickens to develop immunity to some forms of Marek's).
Instead, I begin breeding from old stock at least over one year of age & older if I could that appeared healthiest. I have built a resistance in my flock as I have not had a death in a couple of years.
Back in the 1970s, the commercial industry were losing about 1.5% monthly. The vaccines were developed for the commercial industry. The industry vaccinated in the embryo in the egg. Nowadays, the losses in the industry to Marek's have ceased. Some Marek's strains are more virulent than others.
Some infected birds never show any symptoms. If birds are not vaccinated, they may be immune, or they may have been exposed and it show up later -- cannot tell.
The virus may be virulent and many birds in a flock will die over a relatively short time--or a very "weak" virus that infects few birds. You may have only one bird at a time--over a number of years, die after showing the symptoms. Sudden death may indicate Marek's--you must do a necropsy to be sure. It's appearance in a flock is not a death-knell for them all. (Or it can be.)
I confirmed that what I was seeing (as classic Marek's) because I sent a couple of birds to the lab. This is the only way to confirm that it is Marek's.
One more thing: you CANNOT disinfect for Marek's and you CANNOT get rid of it. Marak's is NOT carried in eggs. You CANNOT know if your birds resistant or immune.
Pros of vaccination- some, but not complete, protection against a potentially devastating virus. Peace of mind.
Cons of vaccination- cost, both in time and money, if you do it yourself. But certainly cost is always a factor. If you have a closed flock (no new birds in, breed all your own replacements, no biosecurity breakdown)then it is hard to justify the cost.
A vet who knows about chickens told me:
Quote: ~The reality is that companies that develop vaccines do so with the production market in mind and since vaccination has to occur at day one for the production market, that is where the energy and money have been focused. Those of us who are small time chicken lovers may reap the benefits but are not the focus. Hence, the lack of a marek's vaccine for 12 week old (pick any age) pet chickens on the market. I remember from school that there were flocks in multiple countries that had reported resistance factors to Marek's, as well as, to other diseases. And by default, we must assume there are also susceptibility factors that run in lines, even if it is just the lack of a resistance gene . . .
~The reason chicks must be separated from unvaccinated birds is that the vaccine is not effective until the chicks' immune systems have had a chance to respond. This takes days to weeks (by 3 or a poor immune system is likely to blame). The vaccinated chicks aren't a danger to other birds. It is the other way around. An unvaccinated bird may still transmit the virus to your newly vaccinated chicks. Remember that at its best the vaccine isn't 100% effective in a flock or in an individual bird. Some birds may not be protected at all (prior exposure to disease, poor vaccination husbandry, other current illnesses, ineffective immune systems, etc.); and there are many birds that end up with lesser cases of Marek's because they have been vaccinated but are not fully protected from getting it. The current thought is that the shedding time is shorter in vaccinated birds that do happen to get the virus.
HOPE THIS ALL HELPS!
