Moving Forward- Breeding for Resistance to Marek's Disease

[feather13]

are you talking about the mareks vaccine or coccidosis or both?

We ordered our day-old chicks from Murray McMurray's and they were supposed to be vaccinated for both coccidiosis and Mareks.

One of our Phoenixes did get vet-confirmed coccidiosis when she was around five months old, although I understand that vaccines aren't 100% effective. I initially thought she had Mareks since some of the symptoms are similar and was going to euthanize her, but treated the whole flock with Corid and she recovered.

 

[ackie]

oh I just realized how old this thread is. I guess the original breeding project isn't around anymore?

 

[microchick]

if a mareks resistant bird is exposed to mareks, do they become a carrier like they would if theyd had the vaccine?

I would expect them to be just because vaccinated birds can still be carriers once they are exposed.

Scrubbing with Oxine is a good preventative but don't become overly confident that you are going to eradicate the virus by scrubbing an area with it. Marek's disease is transmitted through contaminated dander not only from your birds but from wild birds and other people's flocks in your area. It's in the air.

All you can do is what you can do. What you have to remember is that it still around you no matter how well you scrub or disinfect.

 

[EggSighted4Life]

if a mareks resistant bird is exposed to mareks, do they become a carrier like they would if theyd had the vaccine?

As a person who actively breeds for resistance to Marek's.. YES 100% birds that show resistance are still exposed and carrying it IF you have seen it and/or have a diagnosis.

It (Mdv) is stated by the state poultry vet at UC Davis in California to be "ubiquitous" in poultry environments.

The idea is not that we eliminate Mareks but that we breed a better bird..

They MAY still succumb as they AGE with DIFFERENT symptoms than those that appear in the juvenile birds.. IS the newest revelation made known to me via another persons experience/diagnosis.. as our bodies age our immune system declines and what it once fought or controlled well it may no longer continue to do so.. I'm in my 40's and despite having more confidence and skill (mentally) there are some things my body just will not comply with like it did in my 20's.. I have less flexibility and strength (physically). To wit any ELDER bird who start to show symptoms will be culled as quickly as a younger one, in MY "breeding for resistance" program.. there is NO baby the bird along with antibiotics and anticoccidia-stats.. that's NOT resistance.

I'm sure I'll never know for sure how it got here but I'm hoping that in the future my losses will not be so high. I'm not sure I can stand losing 2-3 chickens a year to this.

I'm sorry for your loss.

It has hit hard here this past fall as well.

For you it sounds like ordering vaccinated birds is the right thing to do, which I see you've handled. And a Carolina coop to boot, congrats on your new and happier adventure!

 

[ackie]

it's so weird to think that stronger birds will still carry it

 

[microchick]

As a person who actively breeds for resistance to Marek's.. YES 100% birds that show resistance are still exposed and carrying it IF you have seen it and/or have a diagnosis.

It (Mdv) is stated by the state poultry vet at UC Davis in California to be "ubiquitous" in poultry environments.

The idea is not that we eliminate Mareks but that we breed a better bird..

They MAY still succumb as they AGE with DIFFERENT symptoms than those that appear in the juvenile birds.. IS the newest revelation made known to me via another persons experience/diagnosis.. as our bodies age our immune system declines and what it once fought or controlled well it may no longer continue to do so.. I'm in my 40's and despite having more confidence and skill (mentally) there are some things my body just will not comply with like it did in my 20's.. I have less flexibility and strength (physically). To wit any ELDER bird who start to show symptoms will be culled as quickly as a younger one, in MY "breeding for resistance" program.. there is NO baby the bird along with antibiotics and anticoccidia-stats.. that's NOT resistance.


I'm sorry for your loss.

It has hit hard here this past fall as well.

For you it sounds like ordering vaccinated birds is the right thing to do, which I see you've handled. And a Carolina coop to boot, congrats on your new and happier adventure!

Two minds with the same thought.

I have no illusions about the vaccinated birds that I have brought into my flock of Marek's positive chickens that they aren't exposed to and carrying MD.

And I agree 100% about your observations and experiences in breeding for Marek's resistance. To be resistant to anything, a chicken must be exposed to the contagion and not only survive it, but live to breed chicks that are also resistant.

As for what you notice as you age in your own body.....I hear ya loud and clear!

 

[EggSighted4Life]

it's so weird to think that stronger birds will still carry it

It's been a fantastic wake up call and education that ELIMINATES any fear I had about Covid 19.

There are bacteria and viruses affecting us.. and actually supporting our lives which is not possible without them!

Genetics, followed by AND heavily influenced by nutrition IS the foundation to immunity. Best wishes to all for strong health!

 

[ackie]

im not sure if I agree that resistant birds (not from the vaccine) are carriers.

you can be exposed to a contagion in general and garner a resistance without becoming a carrier.

example, the chicken pox vaccine exposes you to chicken pox and forces your body to build up antibodies against chicken pox, but it doesn't make you contagious with chicken pox and able to spread it to others.

the mareks vaccine is such that the bird gets some resistance against mareks and then basically becomes an asymptomatic carrier. but I don't know that a bird with a natural immunity would be the same way.

example, humans with 1 copy of the gene for sickle cell anemia have a higher resistance to malaria, as it changes their blood cell shape & malaria affects the blood cells so they can actually fight it. I dont know if those people are effectively asymptomatic spreaders while they're infected or not, but as less of the virus can take hold in them, I suspect theyd be somewhat less contagious

biology isnt as cut and dry as to say that birds resistant to mareks are definitely carriers. you'd have to know what is causing the resistance.

another example, herpesvirus in humans stays in your body forever, but it can only be spread while its actively shedding, and that most often coincides with an outbreak (asymptomatic shedding can happen but is less likely). so those people are only "contagious" in any measurable amount when they have symptoms, even though they always have the virus. having a better immune system will cause fewer outbreaks, as in fewer instances of shedding and spreading the virus, which means that being healthy in general makes you spread the virus significantly less.

I know my thoughts are kind of jumbled here so I'd be happy to explain more if something doesn't make sense. but the long and short is...without knowing what is causing the natural resistance, you cant really know if theyd be contagious or not.

 

[microchick]

Studies show that exposed birds, even though they survive and are resistant still carry the virus in their dander.

This quote is directly from the Merck Veterinary Manual.

Transmission and Epidemiology​

Marek disease is highly contagious and readily transmitted among chickens. The virus matures into a fully infective, enveloped form in the epithelium of the feather follicle, from which it is released into the environment. It may survive for months in poultry house litter or dust. Dust or dander from infected chickens is particularly effective in transmission. Once the virus is introduced into a chicken flock, regardless of vaccination status, infection spreads quickly from bird to bird. Infected chickens continue to be carriers for long periods and act as sources of infectious virus. Shedding of infectious virus can be reduced, but not prevented, by prior vaccination. Unlike virulent strains of Marek disease virus, which are highly contagious, turkey herpesvirus is not readily transmissible among chickens (although it is easily transmitted among turkeys, its natural host). Attenuated Marek disease virus strains vary greatly in their transmissibility among chickens; the most highly attenuated are not transmitted. Marek disease virus is not vertically transmitted.

End of quote.

Then there is Typoid Mary to consider who was exposed to Typhoid Fever, never developed the disease but spread it to everyone she met because she was a carrier.

Chicken Pox lives on in the host's body, sometimes colonizing at the base of nerves to rear it's ugly head years later as shingles. The only way a person can get shingles is from the herpes zoster virus. Now, shingles aren't catching but if a person who hasn't had chicken pox comes in contact with the fluid from the blisters caused by shingles, then they can come down with chicken pox. Ask me how I know that one....which I learned the hard way and I'm a retired nurse, LOL. Chicken Pox can also be 'silent' in nature. Meaning you can have them and not know you have them. The symptoms might be really mild and you may even not have a rash...once again ask me how I know that one.

To think that resistant chickens cannot spread MD is a misconception of the disease. I will put it this way. IF you have Marek's disease in your flock, confirmed by a medical professional, then your entire flock is carriers of the disease whether or not they show symptoms. Resistant birds are carriers. As I stated earlier, resistance does not mean immunity. Resistance means they are less likely to be killed by the disease then birds that are susceptible.

My Egyptian Fayoumis, while resistant to Marek's Disease, are still carriers of the disease that infected our property. Vaccinated birds while resistant to the disease are still carriers of the disease.

Some breeds of chickens are more susceptible than others. Silkies, Seabrights, Cochins, Buff Orpingtons to name a few are VERY highly susceptible to Marek's Disease. Other birds like Fayoumis and naked necked Turkens are resistant to the disease. The closer the bird is to it's wild state (one of the reasons they suspect a Fayoumi is more resistant than a hybrid specialized breed) is because their genetics are closer to chicken genes in the wild state.

I suspect that Marek's Disease is a byproduct of science and breeders trying to create chickens that produce large amounts of eggs and look pretty while they are doing it.

​

 

[EggSighted4Life]

Some breeds of chickens are more susceptible than others. Silkies, Seabrights, Cochins, Buff Orpingtons to name a few are VERY highly susceptible to Marek's Disease.

Not in MY anecdotal experience.. The Silkies I bred NEVER showed any symptoms and there were a whole lot of them.. I even got reports back that chicks from my stock were the only ones surviving a distant outbreak several years AFTER they had left my place BEFORE any diagnosis and while still freshly incubated... They kept bringing bird from from unknown places plus added in some hatchery sex links.

MAYBE it matters how virulent the time of year is AND at what age they're first exposed..

There was ONE gene identified that actually showed resistance. Whether or not one has that and WHICH gene it was or how it MIGHT effect carrier status.. that I do not personally recall if it had been reported.. It's a lot of information to try and retain.. and requires repeated AND updated review on MY part in order to maintain and semblance of comprehension.

im not sure if I agree that resistant birds (not from the vaccine) are carriers.

I'm not sure if I agree with your take either.. but I do gather what you are expressing and will take the time to look and consider further.

Noting the KEY is discussion towards comprehension and hashing it out in a civilized manner as appears to be going on here!

I see lots fascinating thing to further my over all understanding pertaining to LIFE!

Interesting point.. yes Marek's writes itself into the dna somehow but does indeed NOT transmit vertically!!

Thank you guys for taking the time to express the reasoning behind your comprehension.