ALAMOSA VALLEY COURIER (Colorado) 23 August 03 Valley 'gators join war against West Nile virus (Teresa L. Benns)
Mosca: As the infection rate for the West Nile virus escalates, studies continue to determine exactly how and under what conditions the disease is transmitted.
Eight Colorado residents have died from the virus and recent statistics show West Nile has infected 638 statewide.
Thursday an Associated Press release reported that several residents of the Denver Zoo, all of different species, died recently from West Nile.
Center for Disease Control (CDC) researchers in Fort Collins are three months into their study of San Luis Valley reptiles to determine what factors contribute to the development of the virus and how these factors might explain its development and control.
Mosca Alligator Farm owner Erwin Young delivered 22 young American alligators to the Fort Collins CDC laboratory in June to participate in the study. CDC researchers and students visited the Alligator Farm in Mosca earlier this summer to randomly test the reptiles for signs of West Nile or immunity to the disease. Blood draws were obtained from both younger and adult alligators.
The Fort Collins CDC laboratory, in collaboration with Florida University also imported alligators of the same species from Florida for the study.
"The study is going great," Epidemiologist Dr. Michael Bunning reported Friday, Aug. 22.
"Alligators are somewhere between horses and birds," on the West Nile transmission scale, he said. Phase two of the study will determine whether alligators already carrying the disease can infect uninfected mosquitoes.
"Crows and blue jays have viremias of between nine and 10," Bunning said. "We thought equines played a role, but they're only moderate hosts. Alligators are between five and six on the scale."
Bunning emphasized he does not intend to make the alligator viremia statistics a "smoking gun," but simply wishes to pinpoint "the primary cycle. We're looking at overwintering mechanisms that may play an additional role in disease transmission."
Bunning explained earlier in the testing process why the CDC chose to study the alligators.
"Reptiles are being looked at for West Nile because they are cold-blooded," he explained. "We think water temperature might play a part. "
Alligators usually are raised in waters where temperatures average about 90 degrees to improve the reptiles' growth rate.
`Several Florida alligators died last year from the virus after the water in their pen slightly exceeded the 90-degree range. Studies will focus on the infection rate experienced by alligators in water temperatures averaging 80-90 degrees.
"We will be infecting the alligators via infected mice to mimic what could happen," Bunning said.
"Different infection methods will be explored and then the results will be evaluated. Not all mosquitoes feed equally on different types of alligators."
"Our alligators live in 80-87 degree water," Young said. "We've been told all these years by the Rockefeller Wildlife Habitat and Refuge in Louisiana that 89- degree water is the perfect temperature."
Researchers hope to discover whether higher water temperature is the main culprit and if stress plays a role in the infection rate, Young added.
The Mosca farm brought 100 baby alligators from Florida 16 years ago to raise in the geothermal springs off Hwy.17.
The alligators clean up dead fish from the fish farm Young operates on the site, and the reptiles in turn provide entertainment for tourists and educational opportunities for local school children.
"All our random testing was negative," Young said. "But they will eventually test them all individually."
The study should be completed by November, Bunning said.
Background on West Nile S cientists meeting in Denver at a Tropical Medicine and Hygiene conference last November marveled then at the swift evolution of the West Nile virus, which began in Africa in 1937.
The new strain of the disease, New World West Nile began killing birds in Israel in 1998 but did not become a killer virus until migrating to the American continent in 1999.
Some 212 Americans died of West Nile last year and another 3.605 survived the virus. Researchers now believe West Nile can be transferred by pregnant women to their unborn children and can infect breast milk.
The virus also can be transmitted through blood transfusions and organ transplants.
West Nile transmutates and becomes more virulent as it travels further across the country. Thirteen thousand horses contracted the virus last year and over a third of the animals died.
The rapid advance of West Nile has scientists worried. Originally mosquitoes from hot and humid climates were most likely to carry the disease.
Now some 37 types of mosquito are potential carriers.
Valley 'gators join war against West Nile virus