Not an Emergency...Marek's in the Flock

[mightymax]

1Quote:
Hey seminolewind...here's a possibility. Perhaps the Marek's virus can lie dormant in a chicken for an extended period of time and only return to its active status as a result of some physiological insult to their immune system. Now if that doesn't open up a whole new can of worms, I seriously don't know what will !!!

I'll leave you now so you can formulate your questions...lol !!!

Signed,
-one of your Think Tank buddies-

aka

-kim-

 

[Nambroth]

Hey seminolewind...here's a possibility. Perhaps the Marek's virus can lie dormant in a chicken for an extended period of time and only return to its active status as a result of some physiological insult to their immune system. Now if that doesn't open up a whole new can of worms, I seriously don't know what will !!!

I'll leave you now so you can formulate your questions...lol !!!

Signed,
-one of your Think Tank buddies-

aka

-kim-

Actually, this is exactly what herpes viruses are known for. Creating latent copies (dormant if you will) in the host's cells, then becoming 'active' again when the opportunity strikes. So to speak. That's a very broad simplification of it. Science is still trying to fully understand RNA and DNA viruses that do this.

 

[mightymax]

@Nambroth ...
...Thank You !!! I knew I must of read that somewhere before because after I wrote it and reread it, I thought..."Hmm,,,that sorta sounds like you (meaning me) might actually know what you're talking about"...LOL !!!

Thanks for giving me my Feel Good Moment of the day !!!

-kim-

 

[seminolewind]

https://en.engormix.com/MA-poultry-industry/forums/mareks-disease-range-paralysis-t5964/p0.htm#17911

You can sign up and ask questions, one of mine was answered by the Vet that started the thread!

 

[seminolewind]

...

...what an image that conjures up in my head !!! There goes a half dozen or so skinny-assed chickens, followed in hot pursuit by a crazy ol' chicken lady in a big floppy hat holding an enormous jar of freeze dried meal worms screeching, "Here, here now chickie, chickie you can't have any pudding 'til you eat all your meat" all the way down the block !!!

<any fans of 'Jethro Tull' out there

>

Oh yes I'm a fan of Jethro Tull. Does that give our ages away?
My skinny chicken of the week is named "Mangia" , and she's eating like a pig right now.


Oh boy...that was fun !!! (not that I picture you that way of course

...lol !!!)

Yes you do! LOL!

OK...back to the business at hand.
Regarding those that were exposed 4-5 years ago and whether or not they should all be considered immunosuppressed, I would definitely tailor my
husbandry practices to accommodate the notion that they were. I'd rather err on the side of caution with this disease. But the question still remains, When those chickens who were exposed to MD 4-5 years ago die, what will be written on their death certificates? Death by Marek's or Death by Unknown/Secondary Illness/Other ???

well, my last 3 necropsies were Negative for Marek's, cause of death? Aspergillosis and enteritis, Liver cancer and enteritis, and capillaria, enteritis, e. coli and cocci. I just can't get past the negative Marek's. I thought that any exposed chicken would be positive for Marek's, not just an active tumor ridden one. I'd have to agree that death was secondary to Marek's in some cases.
I don't know what the correct answer to that would be...Death Suspect for Marek's with Extenuating Circumstances...IDK

I really haven't
got a clue !!! If this were a perfect universe and the world actually did revolve around me (hahaha !!!) I would categorize ALL the exposed chickens' deaths as Marek's deaths and be done with it. Why, you ask? Well, since 'I don't know' just doesn't give the disease (nor my chickens) any justice here, I'd
have to say that...

...sometimes we just have to take it on faith...


For me anyways, that one statement can answer many of those open-ended questions that we all have when we get to talking about MD.
I'm not a religious person by design, tending to lean more towards the scientific, but I do consider myself to be spiritual. and as such, sometimes I find
that by just letting things 'be' for a bit, the answers will eventually come and the questions will usually resolve themselves. Now as high and mighty as that may sound, I'll be the first one to tell you that although faith is something I believe in, it is, without a doubt, not what I am always able to trust nor utilize in my everyday life...lol !!!

Anyway, back at the ranch...

Every one of my chickens that has presented with symptoms that qualified it to carry the title of 'Marek's Disease' victim number so-and-so, has been a ravenous (albeit, rather anorexic-looking) little wisp of a thing. They hadn't always been that way. Only when the symptoms become most pronounced have they been able to succeed at the seemingly incongruous task of eating like they have a hollow leg AND looking as if there'll be no tomorrow. Don't know why that is...malabsorption, MD induced hyperthyroidism, just can't seem to get in their mouth...could be any number of reasons. All I know is that mine were kinda like me...all about food up until the very end!

yes, some of my chickens are thin, and some are like those ravenous and anorexic looking, or eat but not enough. That's a good way of describing it, like they have a hollow leg. I wish I knew why, malabsorption is a better probable than not eating enough.

I wish I knew if something could be done about it. It just seems that those that survive exposure and live never really get discussed. If the virus does not end up causing death by tumors, what other damage is done to exposed chickens whether vaccinated or not?

And with that, I think I will just let the rest of the questions 'be'...
For tonight anyway!

-kim-
...sorry about the length and the obsessive/compulsive way I use spacing !!! And apparently exclamation marks as well !!!

 

[seminolewind]

Quote:
Sometimes I feel like if I ask a question a bunch of different ways, it will finally be answered , LOL. Interesting, I never thought of the part that says "herpes virus" which means it can have dormant copies. Sometimes I think that we all have important facts but like me, I get tunnel vision and and need a good slap on the head!

So Marek's can lay dormant, awake, and not necessarily grow tumors, but affect a chicken in different ways, like wasting?

 

[Nambroth]

Sometimes I feel like if I ask a question a bunch of different ways, it will finally be answered , LOL. Interesting, I never thought of the part that says "herpes virus" which means it can have dormant copies. Sometimes I think that we all have important facts but like me, I get tunnel vision and and need a good slap on the head!

So Marek's can lay dormant, awake, and not necessarily grow tumors, but affect a chicken in different ways, like wasting?

Marek's is Herpesvirus of chickens. HVT is Turkey Marek's-- Herpesvirus of Turkeys.
Herpesviruses are DNA viruses, which essentially (again this is oversimplified) inject themselves into the very DNA of the host's cells, in order to trick the cell into making many copies of the virus DNA instead of the cell's own DNA. When it is latent-- dormant-- it sits there, with its copies in the cell(s), just chilling out until it becomes active again or the host dies.
If you want to rip your hair out you can learn more about herpesviridae and latency here: http://en.wikipedia.org/wiki/Herpesvirus (I know, it's Wikipedia, but it's helpful for a layperson to get a basic idea!)

I am unclear on exactly when, how, and if Marek's becomes reactivated, and what symptoms we see. I sort of suspect that reactivation of the virus (versus the initial infection) is when we see the more long-term slow advance of problems, such as general wasting, immunosupression, sometimes eye problems. This is, at best, a layman's guess based on what I have read.
When you think of reactivation of the virus, think of it like Human Herpes (Herpes Simplex, the STD) and Chicken Pox. Both can go into latency (remission, whatever you want to call it) and then pop back up later in life. Herpes has cyclical reemergence in humans, usually when the person is under stress or is sick with a secondary issue (sound familiar?) whereas chicken pox comes back as Shingles, but it is still the same virus. It has just taken a different symptom when it reactivates later in the host's life.

 

[Nambroth]

Sometimes I feel like if I ask a question a bunch of different ways, it will finally be answered , LOL. Interesting, I never thought of the part that says "herpes virus" which means it can have dormant copies. Sometimes I think that we all have important facts but like me, I get tunnel vision and and need a good slap on the head!

So Marek's can lay dormant, awake, and not necessarily grow tumors, but affect a chicken in different ways, like wasting?

Change once word in your sentence.

"I never thought of the part that says "herpes virus" which means it WILL have dormant copies."

Herpesvirus will make dormant (latent) copies when it infects a host, regardless of symptoms or lackthereof. It's what makes herpesviruses SO GOOD at what they do. They are a very, very effective virus, and a very ancient one.

Now, the part I don't know in all of this is-- again-- exactly why, when, and how Marek's virus reactivates in a chicken.
So, when we know a chicken has been exposed to Marek's, and has latency, how do we know what symptoms later are for sure Marek's, or are they secondary? Are they taking hold because of a comprised immune system? There are a hundred variables. And it is all guesses at that point.

 

[tridentk9]

Actually, this is exactly what herpes viruses are known for. Creating latent copies (dormant if you will) in the host's cells, then becoming 'active' again when the opportunity strikes. So to speak. That's a very broad simplification of it. Science is still trying to fully understand RNA and DNA viruses that do this.

Exactly!! The problem is that while the disease is latent in the B- and T-cells, well, the virus is still produced in the dander. I think exams as thorough as possible, without stressing the chicken, of feathers and skin, while it won't find many cases may be good for two reasons. The best reason is that you'll get a better idea how that bird is doing and spending time with it (treats anyone?).

As far as the hollow leg- Marek's disease does cause problems with the normal bacteria in the gut. I *think* lactobacillis is fine, it's the others that go haywire. And since the gut is going crazy parasites will take advantage. Funny, I was just reading about this Friday or Saturday.

I also found this older article from 1971

Abstract:
Parameters of infection with Marek's disease herpesvirus (MDV) were studied in a flock of naturally infected White Leghorn chickens during a 76-week period. Infection appeared to persist indefinitely in the host chicken although the virus titers were variable and frequently low. Transmission of infection by contact was demonstrated for some 76-week-old survivor birds and seemed related to the titer of viremia and presence of virus in the integument. Titers of Marek's disease (MD) precipitins peaked prior to the 28th week, and in a few cases eventually disappeared; however, antibody detected by the indirect fluorescent antibody test remained undiminished. The persistence of precipitins appeared related to persistence of viral antigen. Birds with high virus titers died more frequently of MD than other birds, but virus pathogenicity could not be implicated as a determinant of survival. Duration of survival was related directly, although not causally, to antibody titer. Response differences among sire families were noted, but progeny tests showed that absence of detectable viremia was unreliable as a marker for genetic resistance.

The current lab tests may give different results plus different strains may also respond differently in the body. But the original strain is still active so some birds may still respond this way.

As a curiosity- an individual bird may be affected by two different strains. A flock may also have different strains affecting it as well as multiple diseases.

 

[Nambroth]

As a curiosity- an individual bird may be affected by two different strains. A flock may also have different strains affecting it as well as multiple diseases.

Yes. And no way for the layperson to distinguish them. qPCR, to my knowledge, just looks for the genetic markers of the MDV-1 species of Marek's virus. I don't think anyone but the people deepest into research even look at strains. I don't think average lab tests do.

There are more variables than one can possibly account for. We guess, at best.