Louisiana's Alligator Conservation Program Under Threat From West Nile Virus - American Veterinary Medical Association (AVMA) Annual Convention

Main Category: Veterinary
Article Date: 22 Jul 2008 - 1:00 PDT

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Veterinary professionals attending New Orleans at the American Veterinary Medical Association (AVMA) annual convention, held July 18-22, will have a chance to learn more about one of the area's most remarkable industries and conservation efforts - Louisiana's alligator ranches.

Louisiana has the world's largest alligator farming industry, estimated at $60 million, and alligator ranchers here work in cooperation with conservation efforts in what has become an international model for rebuilding populations of wild alligators. Dr. Javier G. Nevarez, of the Louisiana State University veterinary school, will speak at 1 p.m. July 22 about the alligator conservation and ranching programs in Louisiana and discuss the biggest threat to these programs - West Nile virus.

Louisiana's modern alligator ranching industry was born in the early 1970s as the result of an environmental crisis. The alligator population had dropped to just 100,000 in the wild and were listed as an endangered species from 1967 to 1981. With the oversight of the Louisiana Department of Wildlife and Fisheries, a ranching and conservation program was developed that has benefited both alligators and the owners of property where alligators live.

Approximately 80 percent of alligator habitats in the state are privately owned, so Louisiana sought to make maintaining an alligator swamp an asset under the conversation program. The program allowed controlled harvesting of the alligators by property owners for profit and introduced, in the 1980s, alligator ranching.

Every summer, ranchers pay a fee to the property owners and are permitted to collect wild alligator eggs. The eggs are hatched and the juvenile alligators mature inside indoor pens. After about a year, the rancher must return alligators representing 14 percent of the total eggs collected to the wild.

This is roughly the same percentage that would have survived if they had grown up in the wild, but the ranched alligators are bigger - the size of a five-year-old alligator--because of the controlled conditions in which they have been raised.

"This program is responsible for bringing the alligator population back to a sustainable level and is used as a model of conservation across the world," Dr. Nevarez says. "This program has been responsible for restoring the wild American alligator from being a species that was threatened to a very manageable population estimated at over 2 million."

More recently, Louisiana's alligator ranching and conservation efforts have been hit by a new and unexpected threat: West Nile virus (WNV). Dr. Nevarez explains that ranchers discovered the alligators in their facilities were getting WNV when they started getting skin lesions, much like the lesions often found on humans with the disease.

Dr. Nevarez said 30,000, out of a captive population of 400,000, died from 2003-2005, but in the last two years, the spread of the disease has been stopped due to vigorous mosquito-control programs. WNV has a mortality rate of 60 percent in captive alligators.

"There have certainly been some successes in the control of West Nile virus over the last two years, and most of those have been in mosquito control programs. The ranchers are spraying for mosquitoes and sealing the ranch facilities," Dr. Nevarez explains.

During his educational programs, Dr. Nevarez will discuss what they have learned about West Nile virus in Louisiana. Wild alligators, it seems, are not susceptible to the virus, and it's now believed that the same temperature controls at the ranch that allow the young alligators to thrive have allowed the virus to thrive in what otherwise would be an unexpected host for the virus.

Alligators are somewhat unusual in that they excrete the West Nile virus in their feces, meaning that alligators transmit the disease to other alligators. They also serve as an amplifying host, being able to re-infect mosquitoes. Finally infected alligators pose a zoonotic threat for humans working with them while infected.

For more information about these and other programs at the AVMA annual convention in New Orleans July 18-22, visit http://www.avmaconventionmedia.org.

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Article adapted by Medical News Today from original press release.
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The American Veterinary Medical Association (AVMA) and its more than 76,000 member veterinarians are engaged in a wide variety of activities dedicated to advancing the science and art of animal, human and public health. Visit the AVMA Web site at www.avma.org for more information.