GAINESVILLE SUN (Florida) 19 May 03 Alligators checked for West Nile (Greg C. Bruno)
Six months after University of Florida researchers announced the discovery of West Nile in farm-raised reptiles, state wildlife scientists have begun hunting for the deadly virus in Florida's wild alligator populations.
The effort, a collaborative study between university scientists, alligator experts at the Florida Fish and Wildlife Conservation Commission, and other agencies, will aim to establish an alligator "blood bank" to identify, catalogue and track potential threats from the disease to reptiles - and humans - statewide.
“This is, as far as we know, the only study looking at West Nile in wild alligators populations,” said Dwayne Carbonneau, a wildlife biologist with the state's alligator management section.
“Do we expect to see it in wild alligators?” Carbonneau asked, noting that differences in captive and wild gator environments may restrict the disease's natural spread. “No, we don't.”
“But I've been wrong before.”
In November, after three alligators raised on a farm in Christmas tested positive for West Nile - a flu-like virus native to Africa, West Asia, and the Middle East that can infect birds, horses and other animals, as well as humans - UF scientists began investigating the source of the disease in Central Florida. Initial tests on the farmed animals confirmed the presence of West Nile in alligator brain tissue, said Elliot Jacobson, an expert in reptile disease at the university.
Additional studies are under way to determine if West Nile was responsible for the alligator deaths, he said. Results are expected within weeks.
But while the West Nile study has confirmed the presence of the disease in farmed animals, many questions remain: If the virus is capable of infecting captive alligator populations, are all of the state's wild gators at risk of infection? And are alligators, which appear to exhibit concentrations of the virus on par with wild birds, possible transmitters for the disease?
The answers are only beginning to emerge.
First detected in crows as early as 1999, West Nile has spread from birds and wildlife populations to humans. While the full extent of the virus' effects in the wild are unclear, the disease has been documented in countless endangered bird species, as well as horses, chicken, bats, rabbits - even a New Jersey State Aquarium harbor seal named Sirrus.
The effects on birds may be most profound, however, and some ornithologists estimate that since the virus' introduction to the United States, more than 90 percent of crow populations have been destroyed by West Nile in some of the nation's worst-affected areas.
Whether wild gators will suffer the same fate is unlikely, some say.
“No, I doubt it,” Carbonneau said. “It hasn't wiped out wild bird populations.”
Lisa Conti, director of the state's environmental health division, agreed.
“It's not something we'd expect to see in wild gators,” she said. She said scientists have gone into tissue archives looking for evidence of neurological damage in wild alligators, and found nothing.
Human health consequences of last year's discovery are also being considered.
In 2002, more than 4,100 cases of West Nile were reported in 39 states, with nearly 15 percent resulting in death. In Florida, 28 human cases were reported, with two deaths.
Health experts have long maintained that mosquitoes are the primary route of transmission to humans. When mosquitoes feed on infected birds, and then bite people, animals or other birds, the disease is quickly spread. But the university's alligator investigation has prompted some to question whether gators may also be capable of passing the virus onto insects, and eventually to humans.
"We know birds move it around the state," Carbonneau said. "We know mosquitoes can. Is that the only source?"
For now, answers remain hypothetical, and research continues.
Since mid-April, Carbonneau and state alligator researchers have been collecting blood samples from more than 300 wild alligators in 20 state water bodies, including the Suwannee River, Orange Lake and Lake Kissimmee. Much of the blood sampling was completed last week, Carbonneau said, and university professors, led by Jacobson, are now working to develop a test to rapidly identify the virus in wild reptile populations.
While results may be months away, a number of theories have emerged as to how the virus could have infected the farm in Christmas.
The initial route of transmission was most probably through a mosquito bite, Jacobson said. While scales and tough skin protect the majority of the reptile's body, soft underbellies, tongues and eyelids are often swarmed by the blood-seeking bugs.
Once a gator is infected with a virus, heated cages and high reptile densities create optimal breeding grounds for diseases, Jacobson said, making it easy for gators to transmit illness among themselves.
And while the virus has been positively identified on only one Florida farm, evidence suggests the problem is far more widespread. Other farms in Florida, and Georgia, have reported similar symptoms observed at the farm in Christmas.
How such findings may affect the state's wild alligators, however, remains a mystery.
Alligators checked for West Nile