Tortoise disease divides experts - Scientists discuss burying tortoises (Terry Witt)
|CITRUS COUNTY CHRONICLE
(Crystal River, Florida) 17 January 05
Two of the state's leading experts on gopher tortoises are offering contrasting views about whether a disease that sometimes kills tortoises should be controlled by allowing animals to be buried alive if they test positive for the illness.
Scientists with the Florida Fish and Wildlife Conservation Commission (FWC) say they are attempting to stop the spread of upper respiratory tract disease (URTD) by forbidding the relocation of animals that may be sick.
For a fee, developers are allowed to entomb them in their underground burrows. Money generated from the "incidental take" permit fees is used to purchase gopher tortoise conservation land in an effort to protect what is left of the species in Florida. Tortoises are listed as a species of special concern under state law because their numbers are in decline.
Ray Ashton, founder of Ashton Biodiversity Research and Preservation Institute Inc. in Gainesville, is a critic of the entombment policy, but Dr. Mary Brown, a professor at the University of Florida's veterinary college, supports the policy, with one qualification. She said no one feels good about having animals buried alive in their burrows.
In Citrus County, the issue came to light recently when four tortoises at the site of a future subdivision in Lecanto tested positive for URTD. The property owner was issued an incidental take permit by FWC allowing him to bury the animals in their burrows.
The other 88 tortoises in the colony can also be buried alive because the state's policy assumes, based on statistics, that a large number of the tortoises have probably come into contact with the sick animals. Twelve tortoises were captured at the subdivision site. Four tested positive.
Ashton, who is seeking federal protection status for gopher tortoises, said the blood test used by the state detects antibodies produced by the tortoise's immune system. The test shows whether the animal has come into contact with the disease, but not whether it has the illness, and the test can't predict whether the animal will die from the disease.
He said the test often produces "false positives," and he said environmental consultants who work for developers often don't know what they are doing when they draw blood from tortoises for the test. He said they often don't realize the test is good for only one strain of the virus, when there are eight strains in Florida.
"Killing tortoises that have antibodies is tantamount to killing people who have antibodies to the flu and never get sick," Ashton said.
Ashton, who operates a preserve near Gainesville, likens URTD to "tortoise flu" and states that not all tortoises die from the illness. He said he has studied tortoise populations where the disease was present, and noticed that some tortoises got well and others died. The fact that some tortoises died doesn't portend a statewide epidemic, he said.
He said the state treats URTD as though it is "tortoise AIDS," when it is more like "tortoise flu." And he said the state has done a poor job of using incidental take permit revenue to purchase tortoise conservation land, which is why it is difficult to find suitable habitat to relocate the animals.
FWC attempted to purchase two pieces of property in Citrus County last year for tortoise conservation, but the landowners wanted more than the appraised value, and FWC did not buy the property. State policy prohibits the purchasing of land at more than the appraised value on the tax roll, according to FWC.
Brown said the thought of burying sick tortoises is horrifying to her, but at the same time, she said there is practical side. She said the species is in trouble primarily because their habitat is disappearing as development occurs in Florida. The only way to save the species is to preserve enough good habitat for the animals to survive. She said the incidental take permits serve that purpose.
"You're not going to stop development in Florida," she said.
Having performed necropsies (animal autopsies) on tortoises that died of URTD, Brown said she disagrees with Ashton's view that URTD is like the flu. She said if he could dissect a tortoise that tested positive for the antibodies, but didn't look sick, he would see the lining of the respiratory tract covered with severe lesions.
Those lesions eat away the respiratory tract lining, she said, and even if the tortoise survives, it may not be able to search for food. She said it's often difficult to tell by looking at a tortoise whether the disease has progressed to the point where the animal is gravely ill and is infecting other animals.
But she said the state has found that when sick tortoises are introduced into a healthy population, they invariably spread the disease to healthy animals and cause "die-offs." At one state tortoise preserve in North Florida, she said this was borne out when an unknown person relocated a sick tortoise to a preserve of healthy tortoises. The result was a die-off, she said.
Brown conceded that research on URTD is in the early stages, but she said researchers know considerably more than they did 10 years ago. Brown said URTD it is an aggressive bacteria, and there is no cure. The disease can be spread from animal to animal, but researchers know little about how it is transmitted.
She said Ashton may be correct that tortoises could withstand the disease on their own, but she said that would be true only if there were not manmade pressures heaped on top of the disease. She said tortoise populations are under stress throughout Florida, and an epidemic now could wipe out their populations.