- The Washington Times - Monday, September 1, 2003


The West Nile virus appears to be no worse for people in Virginia this year than last, but wildlife specialists say the illness has been much worse for birds, including endangered peregrine falcons.

Four probable human cases of West Nile had been reported to health officials through last week, said the federal Centers for Disease Control and Prevention (CDC) in Atlanta. At the same time last year, three human cases had been reported.

However, as of Aug. 20, 658 birds had tested positive for the virus — 484 crows, 138 jays, 23 raptors and 13 other species, the Virginia Department of Health reported.

Those figures probably understate the prevalence of the disease, because they include only birds tested by health officials. Most wild birds killed by West Nile are never found.

Mitchell Byrd, of the Center for Conservation Biology at the College of William & Mary, said wildlife rehabilitators receive only a fraction of the birds that are infected.

“Just the tip of the iceberg,” he told the Virginian-Pilot of Norfolk. “I believe this has the potential to be disastrous.”

Other specialists agreed. “I think it’s worse this year. This year we have seen an increase in the number of raptor cases,” said Jonathan Sleeman, director of veterinary services at the Wildlife Center of Virginia in Waynesboro.

Norfolk wildlife rehabilitator Lisa Barlow said she is receiving more calls about sick birds, but many are too ill to save.

Raptors, or birds of prey, which may eat infected songbirds, are being seen in increasing numbers by wildlife rehabilitators. Among raptor species, hawks and owls have been hit hardest. Three peregrine falcons, listed as an endangered species, have been killed by the virus, and blood tests are pending on what may be the state’s first osprey case.

“Different species of raptors have different levels of susceptibility to the virus,” Mr. Sleeman said. For example, he said, “screech owls don’t seem to be affected.”

But the illness is so new to researchers, and wild birds are so hard to study, that apparent differences in susceptibility sometimes may have simple explanations.

, said Robert G. McLean of the U.S. Department of Agriculture’s National Wildlife Research Center in Colorado.

Screech owls, for example, are small and reclusive, and sick ones may be difficult to find.

Among some owl species in Canada, all the sick birds died, Mr. McLean said. Other raptor species seem able to recover, although certain owls seem to have lingering neurological effects.

The Wildlife Center of Virginia took in two peregrine falcons this summer that tested positive for West Nile virus. Both recovered and were released.

Mr. Byrd said the falcons were found when researchers went to the Eastern Shore to put leg bands on this year’s baby falcons.

“We found three of them dead in the [nest] tower and the fourth one quite badly off,” Mr. Byrd said. “Worse, we found the adult male floundering around on the ground underneath the tower. We’ve only got 19 pairs in Virginia. We can’t afford to lose very many of them.”

At least 160 species of birds have tested positive for the virus, as have 28 mammal species and two types of reptiles. Most human cases have been caused by the bites of infected mosquitoes, which may draw virus-laden blood from sick birds. The virus also has been transmitted to healthy birds that have eaten infected prey.

“This virus, at least in [medical] literature, hasn’t been known in mammals, but this virus isn’t following the rules,” said Mr. McLean. “It killed captive alligators and reindeer last year.”

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