Ok folks, I'm going to play devil's advocate here and throw some wrenches into the toxic rat theory.
First, and perhaps most obviously, how come we have not heard about other large constrictors losing color, having greasy butt explosions(GBE's 
), regurges and rolling over and dying? I've scanned the retic, burm, anaconda and blood forums here on KS and found nothing. May mean nothing, but it's something to consider.
Second, with regards to the poison dog food issue, if the dog food was toxic enough to kill dogs and cats, wouldn't it be toxic enough to kill rats too? The only way this makes sense is if someone had a load of rats just up and die after feeding poison dog food and then froze them and sold them. In my estimation, this would have to be a ton of rats, possibly even an entire breeder's collection. From a business standpoint, this would be a hugely risky thing to do, with far worse repercussions in the long run than losing a bunch of stock to some "unknown" cause. But then again, it seems most of these complaints are directly related to XXXL size rats and not other sizes which kind of negates the theory altogether. What about the smaller rodents being fed the same food? I would think that they would succumb to the poison even quicker and in greater numbers. Wouldn't it then make sense that snakes all over the country, large and small, from corns and kings to retics, burms and our beloved boas, would be shedding out color, having GBE's and regurges and dropping dead?
I think it's a bit simplified to look at only the food supply. What about substrates? What about cage cleaners? What about decorations? What about actual cages? Has anyone done any kind of stats to find out who's boas this is happening to? You know, how old the snakes are, their geographical location, what's the housing, feeding, cleaning, what other snakes are present in the collection, what insecticides may have been used recently, what's the source of the actual snakes affected (who bred them or imported them), etc.
Also, if anyone cares to, please contact me to let me know who the suspected rodent supplier(s) is/are. I have only ever bought frozen rats/mice from two suppliers, and only one in the last two years or so, and I am concerned about the possibility of something being transmitted to my collection from the food.
Anyway, I just would like everyone to stop and think about this a little further to see if there is some other culprit(s), because in my mind, the toxic rat thing just doesn't make too much sense. I do believe that it is hugely important that we pin down the exact cause so it can be avoided in the future.
Also, my most heartfelt condolences to anyone who has lost an animal to this particular syndrome.
Billy
