Originally Posted by mightymax
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.
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...
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!!!
Edited by seminolewind - 11/1/14 at 10:40am