GA Press:Frogs, Lizards Unlikely to Carry West Nile Virus

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Posted by Desiree on March 28, 2002 at 00:51:30:

Frogs, Lizards Unlikely to Carry West Nile Virus
Mon Mar 25, 1:54 PM ET

ATLANTA (Reuters Health) - Frogs and lizards that are native to North America might become infected with West Nile virus (news - web sites), but are unlikely to act as reservoirs for the disease, researchers reported here on Sunday.

Mosquitoes spread the West Nile virus after feeding on infected birds. However, it has not been clear if some other species might harbor the virus through winter months until mosquito activity increases again with warm weather.

Scientists from the US Centers for Disease Control and Prevention (news - web sites) in Fort Collins, Colorado have tried to figure out if reptile or amphibian species native to North America are as likely carriers of West Nile virus as their European relatives.

Humans, horses, and other mammals can be infected by West Nile, but generally do not maintain high enough levels for mosquito re-transmission, while some reptiles and amphibians have been shown to be good hosts.

"In Europe, West Nile virus was found to replicate in amphibians and reptiles and be infectious to mosquitoes," Kaci Klenk told Reuters Health. "Since a similar species was capable of transmitting the virus, we kind of expected to see it in the North American species as well," she said.

Klenk and colleagues infected North American reptiles (green iguana) and North American amphibians (bullfrog) to see if they were adequate carriers of the virus.

She presented her findings here at the 2002 International Conference on Emerging Infectious Diseases in Atlanta, Georgia.

Only one iguana and two bullfrogs showed detectable levels of virus in the blood and the highest level seen equaled about half the amount necessary for mosquito re-transmission. West Nile virus also showed up in the spleen and small intestine of one of the iguanas and in the heart of one of the bullfrogs.

All in all, the viral load was considered quite low and most likely not infectious to feeding mosquitoes.

Klenk suggested the reason why birds may be better vehicles for the virus when compared with the iguana and bullfrog could be due to variations in their cells.

"We really don't know why these animals weren't good carriers," she told Reuters Health. "Somehow they don't have the right proteins on their cells for the virus to attach to," she said.

In the future, the group plans to continue testing different amphibian and reptile species, including the garter snake and the red-ear slider, a type of turtle.

Since it first appeared in the Western Hemisphere in New York City in the summer of 1999, the West Nile virus has been found in about 25 US states and the Canadian province of Ontario.

West Nile virus infection produces no symptoms in most people, but can cause a flu-like infection in the elderly or those with weakened immune systems. It can develop into a crippling or deadly brain inflammation.

Frogs, Lizards Unlikely to Carry West Nile Virus

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: Frogs, Lizards Unlikely to Carry West Nile Virus : Mon Mar 25, 1:54 PM ET : ATLANTA (Reuters Health) - Frogs and lizards that are native to North America might become infected with West Nile virus (news - web sites), but are unlikely to act as reservoirs for the disease, researchers reported here on Sunday. : : Mosquitoes spread the West Nile virus after feeding on infected birds. However, it has not been clear if some other species might harbor the virus through winter months until mosquito activity increases again with warm weather. : Scientists from the US Centers for Disease Control and Prevention (news - web sites) in Fort Collins, Colorado have tried to figure out if reptile or amphibian species native to North America are as likely carriers of West Nile virus as their European relatives. : Humans, horses, and other mammals can be infected by West Nile, but generally do not maintain high enough levels for mosquito re-transmission, while some reptiles and amphibians have been shown to be good hosts. : "In Europe, West Nile virus was found to replicate in amphibians and reptiles and be infectious to mosquitoes," Kaci Klenk told Reuters Health. "Since a similar species was capable of transmitting the virus, we kind of expected to see it in the North American species as well," she said. : Klenk and colleagues infected North American reptiles (green iguana) and North American amphibians (bullfrog) to see if they were adequate carriers of the virus. : She presented her findings here at the 2002 International Conference on Emerging Infectious Diseases in Atlanta, Georgia. : Only one iguana and two bullfrogs showed detectable levels of virus in the blood and the highest level seen equaled about half the amount necessary for mosquito re-transmission. West Nile virus also showed up in the spleen and small intestine of one of the iguanas and in the heart of one of the bullfrogs. : All in all, the viral load was considered quite low and most likely not infectious to feeding mosquitoes. : Klenk suggested the reason why birds may be better vehicles for the virus when compared with the iguana and bullfrog could be due to variations in their cells. : "We really don't know why these animals weren't good carriers," she told Reuters Health. "Somehow they don't have the right proteins on their cells for the virus to attach to," she said. : In the future, the group plans to continue testing different amphibian and reptile species, including the garter snake and the red-ear slider, a type of turtle. : Since it first appeared in the Western Hemisphere in New York City in the summer of 1999, the West Nile virus has been found in about 25 US states and the Canadian province of Ontario. : West Nile virus infection produces no symptoms in most people, but can cause a flu-like infection in the elderly or those with weakened immune systems. It can develop into a crippling or deadly brain inflammation.

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