The Heat Is Online

WNV Decimating Bird Populations in Midwest

West Nile virus takes toll on US birds, Sept. 25, 2002

CHICAGO - Every morning Jill Anderson puts out a handful of peanuts for the birds in her backyard in River Forest, Illinois, a suburb of Chicago.

"The crows usually are there and get the first dibs on the peanuts," she said.

In early August, the crows disappeared. Then Anderson noticed the blue jays started looking sick, followed by house finches and goldfinches, chickadees, and most recently she found a dead mourning dove, all apparently victims of the West Nile virus. "I loved the crow family that lived in my yard," Anderson said. "I think they're dead."

The virus, blamed for dozens of human deaths and more than 1,500 cases of illness, is also taking a toll on avian wildlife in a wide section of the United States from Minnesota south to the Gulf of Mexico and from Nebraska east to Ohio, experts say.

A September survey by the National Audubon Society's Chicago region found that crows, which are normally noisy and visible birds, are almost completely absent from parts of the Chicago area. Audubon Monitors also reported unusual numbers of dead or ailing birds of many species.
"For people who really love nature, this is really upsetting to them to see this," said Judy Pollock, the Audubon's bird conservation projects manager.

Birds serve as the host for the West Nile virus, which is spread by mosquitoes to other birds, as well as to humans, horses, squirrels and even canines. The virus, which causes encephalitis, a potentially fatal inflammation of the brain and spinal cord, cannot be spread from person to person or from birds to humans.


Illinois has emerged as the epicentre so far this year for West Nile infections among humans with 457 cases reported as of September 19, 23 of them fatal, according to state officials. The U.S. Centers for Disease Control and Prevention reported that the disease has been seen in most of the continental United States with 1,641 cases of human infection and 80 deaths.

West Nile, which was spotted on the East Coast three years ago, has taken an even bigger toll on birds, with more than 100 species known to be susceptible to the disease.

The virus, which was seen initially mostly in crows and blue jays, has spread to birds of prey or raptors, including hawks, owls and eagles.

An eagle raised in captivity for 12 years at the Bay Beach Wildlife Sanctuary in Green Bay, Wisconsin, succumbed to the virus about a month ago.

"It's hard to lose a bird that you've had so long," said Mike Reed, the sanctuary's curator.
Dr Pat Redig, director of The Raptor Center at the University of Minnesota, said it had its first West Nile virus case on August 23 in a great horned owl. Since then another 40 or so raptors, mostly great horned owls and red-tailed hawks, have come into the centre with the disease. Most of the birds died or were destroyed, according to Redig.

Raptor deaths from the disease have also been reported in Illinois, Indiana, Kentucky, Louisiana, Michigan, Missouri and Nebraska. In Ohio, the disease is suspected in the illness or death of 800 to 1,000 raptors.

"I've been doing this for 30 years and I've never seen anything like this before in wild birds," Redig said.

He said the birds first appear unaware of their surroundings, then lose their ability to stand and eat and finally begin to suffer from tremors and blindness and sometimes seizures.

With no specific anti-viral treatment available, the centre has been using intravenous fluids, stomach feeding tubes and anti-inflammatory non-steroid drugs to treat birds in the first two stages of the disease.


Redig said the centre was exploring whether the disease could infect raptors in ways other than through mosquitoes, including if the virus could be transmitted through a digested meal, taking into account that great horned owls eat crows that might carry the disease.

It wanted to establish if transmission could occur through parasitic flies and whether a vaccine specifically for birds could be developed.

Experts said while West Nile was here to stay in North America, common bird species would not be wiped out and could develop immunities to the disease. Redig cautioned, however, there were theoretical concerns about birds with small populations in restricted geographical areas, such as the California condor.

Emi Saito, West Nile surveillance coordinator at the U.S. Geographical Survey's National Wildlife Health Service in Madison, Wisconsin, said there were concerns that the annual migration of birds south into Mexico, Central America, the Caribbean and South America would spread the disease there.

In fact, the Cuban authorities said last month they were on the alert for any signs of the disease on their island.