Marek vaccine shedding

Poodlemum

Crowing
Aug 26, 2021
2,079
6,578
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Northern Utah
All our chickens came via local feed stores and aren’t vaccinated for Mareks. I placed a combined order with a local chicken mama and we decided to vaccinate the whole order because she didn’t want to accidentally get an unvaccinated chick. Now I’m hearing that vaccinated chicks can shed and kill off the rest of an unvaccinated flock 😭 Is this actually a huge issue? Should/can I keep the new chicks at my parents house until they stop shedding or does it not work like the live people vaccines?
 
I have gotten vaccinated and unvaccinated chicks at the same exact time, and they have been raised together their whole lives. I haven’t had a single problem. I’m not sure where you heard this from, but I don’t think you need to worry because it doesn’t sound true.
 
I have raised both vaccinated and unvaccinated chickens together for 10 years, and never had a known case of Mareks. I always opt for the vaccine when buying chicks from a hatchery. Some people don’t for various reasons. If you live in an area with a lot of chickens or where Mareks is very common, your chickens could be at risk for getting it from wild birds. Once the disease, which is spread in chicken dander and dust, is on your property or nearby, it may remain there for months to years. It takes 2 weeks of no exposure to the virus for chicks to become immune once vaccinated.
 
I was wondering this same thing. If I hatch chicks and immediately brood with vaccinated chicks from a hatchery, my hatched chicks should be fine, right? Or do I need to keep them separate for 2 weeks?
 
For what it’s worth, I just started vaccinating my home-incubated chicks myself as I recently had a few cases of suspected Marek’s in my flock. My understanding is that all of the available vaccines use live virus (a few different strains), so shedding can definitely be expected. However, the reason these strains are safe to use in the first place is that they’re not very pathogenic at all. If you can inject the vaccine strain directly into a day-old chick, it’s not going to kill the bird next door who catches it via shedding, and may even be protective if that bird hasn’t already been exposed to a natural strain.

A separate issue that may be getting conflated here is that the widespread use of these vaccines may be making other strains of Marek’s more deadly. The reason for this is that a flock of vaccinated birds that can survive a deadly strain will nevertheless act as long-term hosts, forever shedding that more deadly strain into the environment once they’ve caught it. This has nothing to do with the vaccine itself shedding, it just means more potential hosts to transmit whatever hellish version might already exist in the environment.
 

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