West Nile Virus Marches West

  • Zoos have helped public health officials monitor the spread of the West Nile virus. Besides concerns about human health, zoos are worried about the birds in their care.

Cooler weather sweeping the Great Lakes region means the end of the mosquito season. It also means a temporary halt to the spread of West Nile virus in the area. But this past summer the virus made headway into the region much faster than experts had expected. The Great Lakes Radio Consortium’s Lester Graham reports:


Cooler weather sweeping the Great Lakes region means the end of the mosquito season. It also means a temporary halt to the spread of West Nile virus in the area. But, this past summer the virus made headway into the region much faster than experts had expected. The Great Lakes Radio Consortium’s Lester Graham reports.

It’s extremely rare that West Nile virus causes severe illness in humans. But it does happen. While most people won’t even realize they’re infected, about one fourth of those infected will exhibit some mild symptoms. However, the virus can cause encephalitis, which is an inflammation of the brain. In very rare cases it can be fatal.

Zoos have been helpful in monitoring the spread of the disease. It was first identified here in the U.S. by the Bronx zoo in the fall of 1999 after crows started dying in the New York area. Since then, zoos across the U-S have kept watch on their birds and animals. In part to protect them and in part to help health officials track the progress of the virus.

Scientists thought the virus would slowly make its way to neighboring states. But, it’s spread much more quickly than expected. It wasn’t supposed to hit states as far west as Illinois and Wisconsin until sometime next year. But it made it even farther west with reports of it in Missouri.

Researchers have learned the virus is carried by birds such as crows, blue jays, hawks and Canada geese. Dominic Travis is a veterinary epidemiologist at the Lincoln Park Zoo in Chicago. He says since West Nile virus infects birds, experts suggested it would spread southward from New York. That’s because many birds, including some infected with the virus would travel south for the winter. Others, though, said it could spread west.

“And, the westward race won. We were fairly surprised that it came past the Michigan and western Ohio area, but we’ve been prepared because we started this surveillance system and started working with the CDC and USDA and everybody last spring for this specific eventuality.”

Travis says zoos across the Midwest started monitoring for West Nile virus this past spring. They worked with local health officials to determine if the disease had spread to birds in the area.

While birds carry the disease, mosquitoes spread it. So, officials at he Lincoln Park Zoo have been trapping mosquitoes and drawing blood from its animals, testing for West Nile virus. They’ve also been working to reduce the chance that animals will be bitten by mosquitoes. Again. Dominic Travis.

“The two strategies are try and limit the mosquito and if you can’t limit the mosquito, limit the contact.”

Most zoos are hesitant to use insecticides to kill the mosquitoes. So, instead, they try to eliminate places where they can breed. Basically, that’s anywhere a puddle of water stands for more than four days. Travis says that helps meet strategy number one, limiting the mosquito.

“So, a) if you don’t have mosquitoes, the risk is fairly low, and b) if you can’t get rid of all your mosquitoes, then you want to stop mosquitoes from biting the animals and so you do things to keep them separate. And those are –depending on the birds, the size, the situation, the zoo– those are keeping them in during mosquito feeding hours or some people have mosquito nets that they’re incorporating and so on and so forth.”

Zoos are especially worried because they’re responsible for some very rare birds, in some cases the last of a species.

At the Saint Louis Zoo, a huge outdoor flight cage and several other outdoor cages make up the zoo’s bird garden. Zookeeper Frank Fischer says outside bird exhibits are at highest risk.

“We’re making sure that, trying to make sure that none of our birds, even the birds in the outside exhibits here in the bird garden don’t contract any of that disease, say, from crows or our blue jays or birds of that type.”

While birds are most at risk of infection, they’re not the only species hit by the virus. In the U.S., as many as a dozen people have died after being bitten by a mosquito carrying West Nile virus. And even more horses have died. People and horses are considered incidental victims. That is, they don’t carry the disease and they don’t spread it. But they can be infected. A veterinarian in southwestern Illinois, Don Van Walleghen, says he’s gotten a lot of calls from worried customers, asking about West Nile virus.

“Basically, they want to know, is it here? Is it a concern for me?”

And because it’s such a recent phenomenon Van Walleghen’s customers have a lot of other questions. They bring in dead birds, wondering if their dog or cat that was playing with the bird might be infected. So far, aside from horses and people, there have been no reports of other animals, livestock or pets, being infected by West Nile virus, or spreading it.

“In humans, if you are a human bitten by a mosquito that had this disease, you could not transmit it to your kids or to anything else. So, at least that limits the disease from even being thought of as any kind of epidemic.”

But it is spreading. Experts hope that weather conditions next year are not good for mosquito production. But even a relatively normal to dry season as this past year was has not seemed to slow the spread of West Nile virus. If next year is wetter, experts say the virus could spread farther and infection rates could rise. That’s why health and agriculture experts are reminding people to work toward reducing the mosquito population next year. They recommend everything from keeping roof gutters unclogged to prevent standing water, to landscaping yards and driveways to eliminate puddles. Anything that will slow mosquito production next year will hopefully slow the spread of the West Nile virus. For the Great Lakes Radio Consortium, this is Lester Graham.

Biologist Fosters Bald Eagle’s Return

In the 1960’s, the bald eagle was in trouble. There were only about 4
hundred birds living in the U-S And in some states, pollution had wiped
them out altogether. But the bald eagle has made an impressive comeback.
The U-S Fish and Wildlife Service recently announced plans to remove it from
the endangered species list. As the Great Lakes Radio Consortium’s Karen
Kelly reports, it’s good news for the scientists who fought to save this