Marek's Vaccination in Unexposed Chicks Over a Day-old

[McChooky]

I considered this, doing it off property is a possibility.

Unfortunately, this is not the case. Vaccinated chickens won't automatically vaccinate others. Every chick has to be vaccinated for it to work. I've also stopped hatching under broodies because it's impossible to prevent exposure that way if the hen is shedding the virus. It makes it a hassle for small hatches because it becomes expensive real fast.

According to this article "The offspring are protected by the maternal antibodies of the mother" https://www.pbs.org/newshour/science/tthis-chicken-vaccine-makes-virus-dangerous

 

[LikeTurkeys]

According to this article "The offspring are protected by the maternal antibodies of the mother" https://www.pbs.org/newshour/science/tthis-chicken-vaccine-makes-virus-dangerous

It's a little bit more complicated than that, and a PBS article doesn't cover much.

Here is my understanding (sorry if it gets a bit complicated!).

There are two different types of immune responses. A humoral or antibody-based response, are fully developed antibodies that bind to antigens (specific proteins on viruses) and prevent them from replicating. Maternal antibodies fall into this category.

A cell-mediated response are killer T-cells that destroy infected cells. This is the kind of response induced by vaccination.

After infection (or vaccination), a certain number of killer T-cells become memory T-cells. When the virus starts replicating again and are encountered by memory cells, they produce a massive number of killer T-cells to fight the infection. This is what produces long term immunity.

These two types of immunities are also commonly known as passive and active immunity.

The level of maternal antibodies varies from chick to chick, and in general active immunity provides better protection than passive immunity. You want to give the chicks time to develop memory T-cells before actual infection, which is why it's so important to keep them from being exposed for 1-2 weeks after vaccination. That way when the chick is exposed, the memory T-cells can quickly generate killer T-cells and prevent symptoms.

Unfortunately, Marek's disease has the ability to become latent, which means some virus won't be seen by killer T-cells. This is why a chicken will never stop shedding the virus, even if it's vaccinated. But vaccination does aid in preventing symptoms and reducing the amount of virus a chicken does shed.

I hope this makes sense. I'll provide sources later.

 

[McChooky]

It's a little bit more complicated than that, and a PBS article doesn't cover much.

Here is my understanding (sorry if it gets a bit complicated!).

There are two different types of immune responses. A humoral or antibody-based response, are fully developed antibodies that bind to antigens (specific proteins on viruses) and prevent them from replicating. Maternal antibodies fall into this category.

A cell-mediated response are killer T-cells that destroy infected cells. This is the kind of response induced by vaccination.

After infection (or vaccination), a certain number of killer T-cells become memory T-cells. When the virus starts replicating again and are encountered by memory cells, they produce a massive number of killer T-cells to fight the infection. This is what produces long term immunity.

These two types of immunities are also commonly known as passive and active immunity.

The level of maternal antibodies varies from chick to chick, and in general active immunity provides better protection than passive immunity. You want to give the chicks time to develop memory T-cells before actual infection, which is why it's so important to keep them from being exposed for 1-2 weeks after vaccination. That way when the chick is exposed, the memory T-cells can quickly generate killer T-cells and prevent symptoms.

Unfortunately, Marek's disease has the ability to become latent, which means some virus won't be seen by killer T-cells. This is why a chicken will never stop shedding the virus, even if it's vaccinated. But vaccination does aid in preventing symptoms and reducing the amount of virus a chicken does shed.

I hope this makes sense. I'll provide sources later.

The vaccine is very controversial. Adding chickens to a vaccinated flock means buying from a hatchery and meeting the minimum to ship or vaccinating our own & isolating them (which opens up a whole new can of worms ). Some just let their old flock die off and wait years before getting more.Personally I wish I'd never vaccinated mine.

 

[McChooky]

Not necessarily. If the flock is vaccinated but not infected, they will not be shedding the virus. Thus chicks will also have to be vaccinated in order to gain immunity. If the flock is vaccinated and infected, they will be actively shedding the virus in small amounts but not showing symptoms.

You don't want unvaccinated chickens to be infected by virus shed by infected vaccinated chickens. Rather, you want to induce immunity by vaccinating them with a look-alike virus (like a turkey herpes virus) that will not actually produce symptoms or spread from chicken to chicken. Precautions have to be taken to prevent exposure - like sanitizing eggs and hatching them in an incubator, as well as keeping the chicks separate for 14 days.

Once vaccinated chicks are carriers for life. They shed the virus by day 7.
https://pubmed.ncbi.nlm.nih.gov/23901761/

 

[McChooky]

The virus spreads quickly to birds that aren't vaccinated once exposed to birds that are vaccinated( Rispens CVI988) https://pubmed.ncbi.nlm.nih.gov/27569836/

 

[LikeTurkeys]

The vaccine is very controversial. Adding chickens to a vaccinated flock means buying from a hatchery and meeting the minimum to ship or vaccinating our own & isolating them (which opens up a whole new can of worms ). Some just let their old flock die off and wait years before getting more.Personally I wish I'd never vaccinated mine.

Why do you wish you had never vaccinated your chicks? A vaccinated chicken is much better off if infected than an unvaccinated one. Also, there are different strains of Marek's disease. If your flock has a particularly virulent one that is resistant to vaccinations, then I might consider starting over. Many however are quite manageable with vaccination.

Once vaccinated chicks are carriers for life. They shed the virus by day 7.
https://pubmed.ncbi.nlm.nih.gov/23901761/

The virus spreads quickly to birds that aren't vaccinated once exposed to birds that are vaccinated( Rispens CVI988) https://pubmed.ncbi.nlm.nih.gov/27569836/

These are both interesting studies. While I knew that vaccinated birds that are infected will certainly spread pathogenic Marek's disease to unvaccinated birds, this shows that the Rispens vaccine which is the most common serotype 1 vaccine used by hatcheries, can actually transmit from chick to chick.

I think the key difference is that Rispens is not pathogenic (meaning it doesn't cause disease), while the real Marek's disease strains are. So it is still advantageous to vaccinate with a non-pathogenic version of the virus first (even if it can replicate and transmit to other chickens), than to have them potentially infected with the real deal and have no prior immunity.

However it does raise an interesting question of whether vaccinating a few chicks with Rispens and placing them with unvaccinated chicks will provide protection to the unvaccinated ones as well. If the unvaccinated chicks have maternal antibodies, it could prevent infection with the vaccinal virus, but it definitely warrants more research as every study I have read indicates that all chicks should be vaccinated, not just a few.

I don't think this applies to turkey herpes virus (serotype 3) vaccines, which are the ones currently available to small farms.

 

[McChooky]

Reasons why I wish I never vaccinated my chicks against Mareks.

#1 Vaccinated flock w/rooster & broody hens can't hatch & raise their own chicks.
#2 Not all places that sell day old chicks offer the Mareks vaccine.
#3 Any chick I buy or hatch from fertile eggs will have to be isolated after vaccinated.
#4 Vaccinated chickens can & do get Mareks
#5 Vaccinated chickens can & do die sometimes.
#6 Vaccinated chickens can be infected & show no symptoms
#7 The vaccination is costly & must be given soon after thawed or tossed.
#8 Once you've had vaccinated chickens on your property you can't have chickens that aren't
#9 Vaccinated flocks cost more .Period.
#10 Vaccinated chickens that were once healthy are now more apt to get other diseases

 

[LikeTurkeys]

Reasons why I wish I never vaccinated my chicks against Mareks.

#1 Vaccinated flock w/rooster & broody hens can't hatch & raise their own chicks.
#2 Not all places that sell day old chicks offer the Mareks vaccine.
#3 Any chick I buy or hatch from fertile eggs will have to be isolated after vaccinated.
#4 Vaccinated chickens can & do get Mareks
#5 Vaccinated chickens can & do die sometimes.
#6 Vaccinated chickens can be infected & show no symptoms
#7 The vaccination is costly & must be given soon after thawed or tossed.
#8 Once you've had vaccinated chickens on your property you can't have chickens that aren't
#9 Vaccinated flocks cost more .Period.
#10 Vaccinated chickens that were once healthy are now more apt to get other diseases

#1 True if your flock is infected and you want to continue vaccinating chicks to prevent symptoms. Not true just because they are vaccinated (before Marek's entered my flock, I had vaccinated broody hens raise their own chicks with no consequences).

#2, #3 True, part of the difficulty of wanting to provide extra protection.

#4, #5 True, but so do unvaccinated chickens if infected. And vaccinated chickens are much better off if Marek's comes through than unvaccinated ones. Chickens don't get Marek's just because they are vaccinated (they have to be infected), this is very important.

#6 True, but would you rather have unvaccinated chickens that do show symptoms??

#7 True, part of the cost of providing protection

#8 Not necessarily. Again, it's highly dependent on whether your flock actually has Marek's or not. Just because you have vaccinated chickens doesn't mean that they will automatically all have Marek's. And you can still add unvaccinated chickens later if you choose to.

If they're not infected, part of your flock will be protected, part not. You will have more losses should Marek's infect your flock, but still better off than if none were vaccinated. It's ok to mix vaccinated and unvaccinated chickens if your flock doesn't have Marek's.

But if they are infected, then unvaccinated chickens that you add will be prone to serious infection. This is regardless of whether your original flock was vaccinated or not. It's just a question of how many of your original flock you're willing to lose.

#9 True

#10 I don't think there is any evidence to support this. But even if there were, Marek's is the most common chicken disease. It is more likely that they will get exposed to Marek's than any other chicken disease (not including minor and treatable ailments like coccidia or bacterial infections here and there).


It comes down to an individual choice on what you want to do with your flock. Cost is definitely a big one (perhaps the biggest) as is the inconvenience of having to vaccinate small batches of chicks. But I don't want to discount the benefits of vaccination over fears that it could endanger your chickens or harm their health.

 

[RoostersAreAwesome]

#10 Vaccinated chickens that were once healthy are now more apt to get other diseases

That’s only true if they also have Marek’s. Marek’s causes a lowered immune system, the vaccine does not.

 

[InterestingChickens]

According to this article "The offspring are protected by the maternal antibodies of the mother" https://www.pbs.org/newshour/science/tthis-chicken-vaccine-makes-virus-dangerous

According to this source of information, if a chicken if vaccinated for Marek's disease while carrying the eggs that will be hatched, chicks will be protected from Marek's for 3 weeks from hatch date.

'If you hatch eggs at home, your hens can also be vaccinated while still carrying the eggs. If the vaccine is effective, maternal antibodies—antibodies from the hen transferred to the chick—will persist in the chick for up to three weeks.'

The virus spreads quickly to birds that aren't vaccinated once exposed to birds that are vaccinated( Rispens CVI988) https://pubmed.ncbi.nlm.nih.gov/27569836/

The vaccine does not give vaccinated birds Marek's - if this was the case it would never have been rolled out as it would be much too risky. It would of destroyed a huge number of flocks around the world who could not afford or be supplied the vaccine. My source for this information is in the link below.

#1 Vaccinated flock w/rooster & broody hens can't hatch & raise their own chicks.

The vaccine does not pass on the disease, it cannot survive in the vaccine form.

'As hardy as this virus is in the feather dander, it is a live virus that dies rather quickly in vaccine form.'

This link contains graphic pictures.
https://extension.psu.edu/mareks-disease-in-chickens

#4 Vaccinated chickens can & do get Mareks

They can get Marek's, but have an 85.3% better chance of not dying than they would without the vaccine.

'This serotype 3 vaccine was shown to be safe and gave overall protection of 85.2%'.

You can read about that here.

#5 Vaccinated chickens can & do die sometimes.

Key word there is 'sometimes'. The Stereotype 3 vaccine has a 85.3% success rate as mentioned above.

#10 Vaccinated chickens that were once healthy are now more apt to get other diseases

Please state your source's.

#3 Any chick I buy or hatch from fertile eggs will have to be isolated after vaccinated.

This is so they do not catch Marek's during the incubation period of the vaccine. This is important for the vaccine to work and for your birds safety, if you happen to have the disease in close proximity. It is hardy any work for the protection you and your bird's will benefit from in the future if your birds do end up catching Marek's.


'Birds must get the vaccine before they are exposed to the virus. Then the birds need about 4-7 days for the vaccine to do its work. That means complete isolation of the chicks for at least this time.'

Same link as the second one. Contains graphic images.
https://extension.psu.edu/mareks-disease-in-chickens

#6 Vaccinated chickens can be infected & show no symptoms

This is the same with unvaccinated birds.

'Birds that are healthy in appearance can be carriers of the disease.'
https://www.business.qld.gov.au/ind...lfare/pests-diseases-disorders/mareks-disease