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

[mightymax]

Hi there Seminolewind...
...Metastasis is basically when malignant, or cancer, cells go from one part/area/location in the body to another part/area/location in the same body via transportation provided by the blood vessels, permeable membranes and/or the lymphatic system.

...Not all birds that are diagnosed as having Marek's will present with tumors. Just like not all of them will present with the eye abnormalities or with the paralysis. But aside from a positive PCR, one of the most definitive symptoms of MD is enlarged nerves. Specifically, the vagus, brachial and sciatic nerves.

I'm sorry. Somethings come up. I'll finish this up in the morning.
-kim*

 

[seminolewind]

Hi there Seminolewind...
...Metastasis is basically when malignant, or cancer, cells go from one part/area/location in the body to another part/area/location in the same body via transportation provided by the blood vessels, permeable membranes and/or the lymphatic system.

...Not all birds that are diagnosed as having Marek's will present with tumors. Just like not all of them will present with the eye abnormalities or with the paralysis. But aside from a positive PCR, one of the most definitive symptoms of MD is enlarged nerves. Specifically, the vagus, brachial and sciatic nerves.

I'm sorry. Somethings come up. I'll finish this up in the morning.
-kim*

I thought the eye abnormalities and enlarged nerves were also caused by tumors, just microscopically small. I also thought that a PCR accuracy is based on amount of viral concentration. Such as my chickens tested negative although I know they have exposure, and Nambroth has experienced the same thing. Active vs inactive?

I can't seem to find anything that addresses what a Marek's exposed chicken dies of several years later when there are no tumors. Is it a life-long immune suppression that Marek's causes? Or is the immune suppression only when the virus is being produced?

Every one of my latest necropsied chickens has lived within Marek's contamination for several years. For some reason my last necropsy was worded as since my hen did not have tumors, it did not have Marek's. I would have had more assurance if the necropsies had said that the hens died of ***** secondary to suppressed immune system secondary to Marek's.

I can't seem to find any information on whether exposure and no tumors ends there or how exposure kills them later on, if it does.

 

[seminolewind]

I found this, I haven't had time to read any of it.............

http://en.engormix.com/mbr-42868/forums.htm

 

[mightymax]

Quote:
Yes and No.
...I think (and I could be wrong, I oftentimes am) that some of the confusion may stem from the use of the term 'tumors'. To me, as I'm sure it does to a lot of people, the word 'tumors' conjures up pictures of tangible things consisting of mass, or substance (i.e. a golf ball sized tumor or a pear shaped foreign body, etc). But I don't think that those are fitting descriptions of what the term 'tumor' means in a MD discussion. Only because the 'tumors' in MD are not necessarily tangible nor do they constitute a mass. Instead, the 'tumors' referenced in MD are (and here's where I believe much of the confusion lies) terminally differentiated B-cells. When invoking an image of a tumor such as these, a picture of a golf ball floating in a pool of blood transversing through a vein, is not one that should be conjured up. It should be imagined as nothing of mass, or substance, but of just individual cells that happen to be carrying a concealed weapon of mass destruction in their pocket. Not something that can be cut out and dissected.
Yes and No.
...Since basically a PCR test makes many copies of a small segment of DNA (or RNA) so that in the end you'll have a much larger sample of identical DNA to isolate from, it's accuracy isn't dependent on viral load, just its presence. That being said, it's a well known fact that PCR testing is not 100% accurate (nor is any test that requires human hands to be an assistant...lol !!!).

Now that I've entirely muddied the already murky waters of even my own mind, I'll rest a bit...lol !!!

Until next time...
Take Care,

-kim-

 

[tridentk9]

I thought the eye abnormalities and enlarged nerves were also caused by tumors, just microscopically small.  I also thought that a PCR accuracy is based on amount of viral concentration.  Such as my chickens tested negative although I know they have exposure, and Nambroth has experienced the same thing.  Active vs inactive? 

I can't seem to find anything that addresses what a Marek's exposed chicken dies of several years later when there are no tumors.  Is it a life-long immune suppression that Marek's causes?  Or is the immune suppression only when the virus is being produced?

Every one of my latest necropsied chickens has lived within Marek's contamination for several years.  For some reason my last necropsy was worded as since my hen did not have tumors, it did not have Marek's.  I would have had more assurance if the necropsies had said that the hens died of ***** secondary to suppressed immune system secondary to Marek's. 

I can't seem to find any information on whether exposure and no tumors ends there or how exposure kills them later on, if it does. 

I wasn't able to verify info from the older (1980-90's) study I found and now that I'm ready to try again, well I just can't find it. Basically it said that the strain: original, v, vv or vv+ had a lot to do with the signs and symptoms. For example very virulent plus (vv+), a new strain at the time, rarely had tumors- though it may have had to do with the speed with which it killed.

From a more recent article:

The pathogenesis of MD can be divided into 4 well-characterized phases: (1) acute cytolytic infection; (2) latency phase; (3) secondary cytolytic phase, and (4) lymphoproliferative disease. Disease usually becomes manifest during the fourth phase. However, after experimental infection of chickens with some strains of MDV, early deaths occurred that coincided with the acute cytolytic stage of infection and occurred between 5 and 21 days post inoculation. This process was named early mortality syndrome (EMS). The acute cytolytic phase occurs 3 to 4 days post infection, when there is cytolysis of B-lymphocytes and activated T-lymphocytes. By days 7 to 13 post infection, atrophy of bursa of Fabricius and thymus is present.

http://m.vet.sagepub.com/content/48/5/993.full

 

[tridentk9]

I found this, I haven't had time to read any of it.............

http://en.engormix.com/mbr-42868/forums.htm

Dr Schat has written some very informative MDV articles.

 

[Nambroth]

Kim is very spot on.... tumors and neoplasms are not always the masses we think of. Simply, they are abnormal growth of cells. Even when they do not form masses, they are often no less damaging to surrounding healthy tissues, organs, etc.

 

[jgoldy2]

I was woundering is Maraks contagious?

 

[seminolewind]

Quote:

Yes and No.
...I think (and I could be wrong, I oftentimes am) that some of the confusion may stem from the use of the term 'tumors'. To me, as I'm sure it does to a lot of people, the word 'tumors' conjures up pictures of tangible things consisting of mass, or substance (i.e. a golf ball sized tumor or a pear shaped foreign body, etc). But I don't think that those are fitting descriptions of what the term 'tumor' means in a MD discussion. Only because the 'tumors' in MD are not necessarily tangible nor do they constitute a mass. Instead, the 'tumors' referenced in MD are (and here's where I believe much of the confusion lies) terminally differentiated B-cells. When invoking an image of a tumor such as these, a picture of a golf ball floating in a pool of blood transversing through a vein, is not one that should be conjured up. It should be imagined as nothing of mass, or substance, but of just individual cells that happen to be carrying a concealed weapon of mass destruction in their pocket. Not something that can be cut out and dissected.
Yes and No.
...Since basically a PCR test makes many copies of a small segment of DNA (or RNA) so that in the end you'll have a much larger sample of identical DNA to isolate from, it's accuracy isn't dependent on viral load, just its presence. That being said, it's a well known fact that PCR testing is not 100% accurate (nor is any test that requires human hands to be an assistant...lol !!!).

Now that I've entirely muddied the already murky waters of even my own mind, I'll rest a bit...lol !!!

Until next time...
Take Care,

-kim-

Kim that's very good information.
I've always understood tumors to be something like invading tissue with specified walls or shape becoming a mass or just something like a pimple or pock. And they multiply or grow to the point of destroying enough tissue to cause illness or death.

Right or wrong, thinking is good, and I consider this something like a "think tank".

I understand the testing consists of 3 components. Gross appearance of tumors and flock history. Histological findings. And a pcr. Now, do pathologists find the first 2 negative and don't bother with the pcr? Is the pcr only more accurate with active tumors? How does actively spewing virus without tumors fit into this?

I guess my 3 necropsies being Marek's negative when I'm sure the chickens are positive leave a question of is that chicken's immunosuppression caused by Marek's , age, or genetics , or something else?

I'm also thinking about whether subclinical clostridium enteritis plays a part in this as a low grade infection secondary to Marek's immunosuppression which may cause wasting in an older chicken.

This makes my head hurt!!!

 

[seminolewind]

I was woundering is Maraks contagious?

That is the major problem, jgoldy2. An exposed chicken, whether they get symptoms or not, are vaccinated or not, still spew dander with infective virus. So if one of your flock is positive, the flock is exposed as well. The vaccine can prevent the tumors, but not stop the virus from spreading rapidly.