Marek's disease

Thanks so much for your reply, that is what it was! I am just a worry wart!

I bought 6 vaccinated chicks from a hatchery in March. I bought an UNvaccinated chick to add to the frock a couple days later. A couple months later, I bought an UNvaccinated pullet. One of my vaccinated chicks started showing signs of Marek's in June. We didn't think it was Marek's bc she had been vaccinated. We actually took her to the avian vet a few times and since she wasn't getting better, we recently had her put down. The vet did a free necropsy and confirmed Marek's. Either the hatchery missed her when vaccinating, or she's one of the unlucky 5% that still get infected after being vaccinated. Or maybe the vaccine only covers certain strains of Marek's?? Anyway, now it's safe to say my other 7 birds are carriers, although they haven't shown any signs...yet.

Now, my question is: If I add a vaccinated bird to my flock, will she be safe since she is vaccinated even though my other birds are carriers? That's what a vaccine is for, right?

Yes but there is the slim chance of a vaccinated bird getting it as you experienced.

Deeya8604 said:

I bought 6 vaccinated chicks from a hatchery in March. I bought an UNvaccinated chick to add to the frock a couple days later. A couple months later, I bought an UNvaccinated pullet. One of my vaccinated chicks started showing signs of Marek's in June. We didn't think it was Marek's bc she had been vaccinated. We actually took her to the avian vet a few times and since she wasn't getting better, we recently had her put down. The vet did a free necropsy and confirmed Marek's. Either the hatchery missed her when vaccinating, or she's one of the unlucky 5% that still get infected after being vaccinated. Or maybe the vaccine only covers certain strains of Marek's?? Anyway, now it's safe to say my other 7 birds are carriers, although they haven't shown any signs...yet.

Now, my question is: If I add a vaccinated bird to my flock, will she be safe since she is vaccinated even though my other birds are carriers? That's what a vaccine is for, right?

Click to expand...

Wish it was this simple!! A lot of us with Marek's would breathe a sigh of relief if this is how it worked in reality.

Marek's vaccines boast a 95% effective rate. I do not disbelieve that this was true back in the day-- but increasingly we are seeing new strains and more virulent strains of Marek's. The most commonly used vaccine might be 95% effective in a commercial farm (which is actually what the vaccines were developed for), but in backyards where there are so many variables (including but not limited to: different breeds, different genetics, different immunities, different strains, different conditions...) I would say that the vaccine is probably, realistically, anywhere from 60-95% effective in mixed backyard flocks with all of these variables.

On top of this: vaccines are not always administered correctly, even at hatcheries. They usually are, but sometimes a chick just doesn't get the correct inoculation due to volume of chicks processed in any given day.

On top of all that: if a chick is exposed to Marek's within the first three weeks of life, the vaccine does not always have enough time to help boost immunity in the chick. And so, the vaccine has a greater chance of "failing". It is why it is vitally important to keep new chicks in strict quarantine for at least 3 weeks before exposing to your flock or to other birds.

So, if you add any vaccinated birds to your flock, they have a high chance of not showing symptoms (this is good, as symptoms can become fatal). But it is not impossible. Woefully, many of us have still lost vaccinated birds added to an infected flock. Most lose them at a much lower rate, but it can still happen.

Vaccines give the chick's body a chance to build immunity by exposing it to a closely related virus (that will not hurt the chicken). It is not a guarantee. It is just a jump-start to the immune system. It can help a lot, but is NOT a cure or a true immunity.

Here is more reading: https://www.backyardchickens.com/a/the-great-big-giant-mareks-disease-faq

Just to bump this topic I have a question for everyone.

I have a pullet showing signs of Mareks but can't be positive. I have her isolated in a dog crate but she is in the coop. I don't have anyplace else to put her but I'm concerned about the other girls. If this is definitely Mareks what can I do to "prevent" the onset of it in the other girls. Clearly they have been exposed already????