Mixing vaccinated and unvaccinated chickens post-Marek’s infection?

[ebot]

Hello all,

Last July I lost my dearest hen to Marek’s. Fast forward to now, and I’ve since lost 3 more hens (out of 13) - a 1 year old brahma, 4 year old speckled sussex, and her daughter, a 15 week old RIR/speckled sussex mix. All were unvaccinated.

Since the last loss, things seem to be settling down, but now I’m looking to replenish my flock. I was planning on breeding for Marek’s resistance (I hatched out 5 chicks last year, 1 has died thus far), but recently I had to move to an area with an HOA that doesn’t allow roosters.

So my question is - if I buy vaccinated chicks (I know to quarantine them as long as possible), will they inevitably contract the virus that has infected my flock and shed it themselves? Would this overload my unvaccinated chickens who have survived thus far?

I’ve read that the Egyptian Fayoumi are naturally resistant to Marek’s. Should I exclusively add this breed to my flock?

If I decide to get a mix of Fayoumis and other breeds, would it be best to leave the Fayoumi chicks unvaccinated but vaccinate the other breeds?

If I did get Fayoumis, should I vaccinate them regardless of their alleged resistance to Marek’s?

I know this is a complicated situation and I appreciate any and all advice, insight, or even brutal honesty. Thanks in advance.

 

[sloanbychoice]

Definitely following this one! I can’t wait to hear what everyone has to say...

 

[pozees2]

Marek's is complicated, and I'm not sure you will get one answer that's better than the rest, but here is my input.
1 - Several years ago I had read numerous times that birds vaccinated for Marek's will shed the virus in a more dangerous form than the one commonly infecting birds, but when I asked the folks at the Colorado State University, they said the virus shed by the vaccinated birds was not one other birds could pick up.
2 - Once a bird is past about 6 months of age its vulnerability to Marek's should be greatly reduced, to the extent that unless they have some other issue affecting the immune system or happened to be among the minority of birds extra susceptible to Marek's, they should be largely resistant. This leads me to believe that the loss of your one year old and 4 year old birds may have been attributable to something else, did you have necropsies done by any chance to confirm that was what they died from?
3 - The vaccination for Marek's most commonly used, last I read at least, was live virus, so vaccinated birds have the virus. That is how their immune systems learn to manage it. I find this a bit confusing to comprehend fully, but what I have read is that the chicks hatch with a certain level of immunity from their mothers, and once that immunity wears off, if they have not been vaccinated, their immune systems are too immature to manage it until they are about six months of age. Ages 6 weeks to 6 months, unvaccinated birds which are not resistant will succumb to it if infected in almost all cases.

Since you are no longer in a position to breed for resistance, your options would be to either buy chicks old enough to know gender from a local breeder who has been breeding for resistance five years or more (that was about how long it took me to stop losing birds to it, although the last couple of those five years I only lost one or two birds), buy unvaccinated sexed chicks and hope for the best, or buy vaccinated sexed chicks and know the vaccine is like sexing, about 90% effective, but that your older birds should be well past the age of vulnerability, and that if the Colorado State University folks are correct, they can't become ill because of the vaccinations of the chicks.

 

[ebot]

Marek's is complicated, and I'm not sure you will get one answer that's better than the rest, but here is my input.
1 - Several years ago I had read numerous times that birds vaccinated for Marek's will shed the virus in a more dangerous form than the one commonly infecting birds, but when I asked the folks at the Colorado State University, they said the virus shed by the vaccinated birds was not one other birds could pick up.
2 - Once a bird is past about 6 months of age its vulnerability to Marek's should be greatly reduced, to the extent that unless they have some other issue affecting the immune system or happened to be among the minority of birds extra susceptible to Marek's, they should be largely resistant. This leads me to believe that the loss of your one year old and 4 year old birds may have been attributable to something else, did you have necropsies done by any chance to confirm that was what they died from?
3 - The vaccination for Marek's most commonly used, last I read at least, was live virus, so vaccinated birds have the virus. That is how their immune systems learn to manage it. I find this a bit confusing to comprehend fully, but what I have read is that the chicks hatch with a certain level of immunity from their mothers, and once that immunity wears off, if they have not been vaccinated, their immune systems are too immature to manage it until they are about six months of age. Ages 6 weeks to 6 months, unvaccinated birds which are not resistant will succumb to it if infected in almost all cases.

Since you are no longer in a position to breed for resistance, your options would be to either buy chicks old enough to know gender from a local breeder who has been breeding for resistance five years or more (that was about how long it took me to stop losing birds to it, although the last couple of those five years I only lost one or two birds), buy unvaccinated sexed chicks and hope for the best, or buy vaccinated sexed chicks and know the vaccine is like sexing, about 90% effective, but that your older birds should be well past the age of vulnerability, and that if the Colorado State University folks are correct, they can't become ill because of the vaccinations of the chicks.

Thank you so much for this detailed reply! I really appreciate it.

Actually, 3 out of the 4 hens I’ve lost to Marek’s have been <1 year old. My first loss, a 1 year old Ayam Cemani (July 2019), and then the 1 year old brahma (November 2019), and then the 4 year old speckled sussex (December 2019) immediately followed by her RIR mix daughter. Funny you mention CSU, that’s actually where I took my Ayam Cemani when I found her partially paralyzed and unable to walk. I did not get necropsies done on the other 3 that died because they were so classic Marek’s - one leg paralyzed, unbalanced walking, then unable to stand at all, all within the span of 1-3 days until they were euthanized.

I know it’s not common to have adult chickens succumb to Marek’s, and I really couldn’t say why this has happened to mine. I haven’t had any pervasive illness in my flock. I’ve had off and on problems with poultry lice but nothing extreme. The only other illness of note is when I had to quarantine and put one of my girls on antibiotics winter of 2018 to fight off a respiratory infection, but she recovered quickly and no one else got sick. I didn’t lose anyone to Marek’s until July 2019.

Strangely, I have a few bantams, including a sebright and silkie (they live in a separate coop/run from my larger mixed flock) who haven’t showed any signs of illness, despite being genetically susceptible.

Thank you for your information on the vaccine! That is probably the route I will take. I know the live virus in the vaccine is a different type than the virus they actually contract, I just wasn’t sure due to conflicting information on the internet whether or not they could still contract the virus that’s already in my flock, and then shed that back out in higher amounts.

 

[pozees2]

Did CSU mention the possibility of lymphoid leukosis? I remember reading some time ago that it could mimic Marek's symptomatically, but I have no idea how it would be diagnosed, and I don't think it's treatable. I know I (and most keepers I would guess) assume one-sided paralysis where they still try to eat for a while and then get depressed and thin and die is almost certainly Marek's, and 99 times of 100 we're probably right, the thing that surprises me is your older birds, but weird stuff happens sometimes for no explainable reason. I'm glad the rest of your flock seems well and that your bantams have shown no sign of illness, whew!