Thanks for a great overview of the problem.
I noticed that ranavirus sometimes manifests by affecting the feet of turtles. About ten years ago I had a large collection of various species of turtles that was devastated by disease. Only two animals survived, a Terrepene and a Cuora and they are still alive today. I spent thousands of dollars trying to discover the causative agent. I got reports from histologists saying that every organ was affected in the diseased animals. One of the most startling symptoms was that the turtles' feet were rotting off.
You also mentioned that wildlife rehabilitators can be part of the problem or part of the solution. About a month after the epidemic I discovered a missing Rhinoclemmys pulcherrima. To my horror I discovered that all four feet had been reduced to skeletons yet the animal was still alive and walking. In retrospect I should have destroyed it, but instead I took it to a wildlife rehabilitation center in Gainesville FL. I explained that I was leaving the country and could not care for it myself. I provided a child's swimming pool as an isolation cage, a supply of antibiotics that had been prescribed by a vet, a stipend for its care, and a donation to the facility. That afternoon I got a call from a friend who sometimes volunteered at the facility. She told me that I had been indicted for animal cruelty and the police were on the way to arrest me. The people who ran the rehabilitation center were animal rights fanatics who would not listen to reason, but she eventually convinced them to drop the charges. I can only hope that they did not release the sick animal into the wild.
In a message dated 10/24/2012 8:47:34 A.M. Eastern Daylight Time, [log in to unmask] writes:
Hi, Bruce,

I've done an overview on Ranavirus here.  I believe your theory is very plausible.  

David Stang  

-------- Original Message --------
Subject: Kingsnake decline, a possible cause
From: Bruce Morgan <[log in to unmask]>
Date: Mon, October 22, 2012 7:15 pm
To: <[log in to unmask]>

Fellow herpers:
As you all know kingsnakes have long been in decline throughout the southeast and have been totally extirpated in many areas of Florida where they were once common such as Paynes prairie. Many other species are in equally bad shape. The general consensus has long been that fire ants were the primary cause, along with roads, habitat destruction, and resulting ecosystem collapse.
There are problems with each of these explanations. Kingsnakes and other species have disappeared in remote wilderness areas, so it is clearly not just rednecks, roads, or lack of habitat.
Long ago I noticed that kingsnakes persisted in small numbers on the islands along the gulf coast. I am told that they persist on dikes in the everglades too, particularly in agricultural areas, but I have not seen them there. Kingsnakes still exist in upland locations further north and perhaps west but I have no personal experience further west. If fire ants were the problem how could they continue to exist on dikes in the glades? Fire ants can fly, and I have often seen them on the gulf coast islands, so there goes that explanation.
If it is a disease there must be either a vector or some other means of transmission. Snakes are not communal animals so direct transmission is unlikely. If there was a vector such as mosquitos then the snakes on my back porch would long ago have died since they can easily be bitten through the screen. Ditto for an aerosol pathogen.
More recently natricines, once the most common of snakes, have disappeared too. Our creeks and rivers are now effectively devoid of watersnakes where there used to be thousands of them, and Steve Christman has for years offered a reward for anyone who can find a male blue garter snake. Natricines are extremely prolific. It certainly isn't lack of food for there are still plenty of small fish.
Let's review what used to be the basic food chain at Paynes prairie: plants>bugs>frogs>watersnakes>kingsnakes. (Yes, I know kingsnakes eat things besides watersnakes, and it is true that there was a catastrophic decline in cotton rats, perhaps caused by fire ants) The point is that kingsnakes used to eat watersnakes and garter snakes both of which eat frogs.
Why do the islands serve as refuges? What is different there from the mainland? Lack of standing fresh water! What needs standing fresh water? Frogs!
I recently read that ranaviruses have been shown to infect various reptiles, so I cannot help but suspect that frogs infected the natricines that infected the kingsnakes. Perhaps the natricines persisted after the kingsnakes simply because they are more prolific.
The kingsnakes on the gulf islands presumably eat lizards, mice, possibly birds, and salt marsh watersnakes. Nerodia clarkii is fairly scarce, lives in brackish water, and thus rarely eats frogs. Likewise kingsnakes living in upland places like Tennessee probably have less contact with frog eating natricines than those living further south in swamps.
There are some holes in my theory such as the presumed persistence of kingsnakes on dikes in the glades where surely there must be plenty of frogs. Or are there? Is it possible that agricultural spraying in the cane fields has reduced the number of frogs thus forcing the watersnakes to eat fish and the kingsnakes to eat the abundant rodents? I don't know.
Moccasins eat frogs and they are doing fine. They have recently been show to carry eastern equine encephalitis without exhibiting any symptoms, but that just proves that they are indestructible. Ditto for bullfrogs.
Even rat snakes are in decline, but there are still some around, especially large adults. Young rat snakes specialize in small frogs and lizards whereas the adults do not. I don't know if hylids are susceptible to ranaviruses or not. Is it possible that their arboreal lifestyle limits exposure to waterborne disease and thus not all rat snakes have died out from eating them?
I don't know anything about ranaviruses or other herp diseases, but cannot help but suppose that the persistence of kingsnakes on small islands may be an important clue. So who does know about these things?
That is why I am writing this, to see if any of you can point me in the right direction or have any thoughts on the subject. Feel free to forward this.
AKA: Bruce J. Morgan
Environmental Designs
POB 1519
Archer, FL 32618 USA
352 495 9748