West Nile bird vaccine looks promising

Washington-The first round of trials to develop a West Nile vaccine for birds has shown a significant reduction in mortality in inoculated American crows, scientists report.

The Centers for Disease Control and Prevention (CDC) in Fort Collins,Colo., carried out preliminary trials, which demonstrated a 60 percent increasein survival rates over unvaccinated birds in lab tests.

"We are very pleased with the initial tests and believe this couldbe an effective tool for protecting some of our most endangered birds suchas Mississippi sandhill cranes and California condors," says Dr. PattiBright, a veterinary epidemiologist.

Bright is director of the American Bird Conservancy's (ABC) Pesticidesand Birds Campaign. Leading efforts for the bird vaccine are the AmericanBird Conservancy (ABC), in partnership with the American Zoo and AquariumAssociation (AZA).

"We are now looking forward to conducting field trials at participatinginstitutions to see how the vaccine performs in real-world situations, outsideof the laboratory," says Bright. "We hope this will be a cross-speciesvaccine."

Real-life catastrophe

First discovered in an infected crow in Queens, N.Y., in 1999, the WestNile Virus' toll on both wild and captive birds has been enormous.

"At this point, it's too early in the game to know what the long-termimpacts are going to be on wild bird populations," says Bright.

Crows, blue jays and hawks have been among the worst hit, but 111 specieshave now been recorded as killed. At least tens of thousands of birds arethought to have been killed by the virus, according to estimates.

The American crow suffers close to 100 percent mortality rates in thewild when infected by West Nile Virus and so was chosen as the test speciesfor the vaccine trials. At the CDC lab, scientists noted a reduction inmortality rates of 60 percent by use of the new injectable recombinant DNAvaccine.

"We're hoping that since crows are so susceptible, if we're ableto get their mortality rate down, we'll do an even better job in other speciesthat are less susceptible to the disease," says Bright.

Down the road

The bird vaccine ultimately would be designed for birds that are in captivity,either companion animal birds or zoo-based birds. Eventually the goal wouldbe to reach endangered species programs or captive breeding programs.

The latest species to be considered for vaccine testing are geese andred-tailed hawks. The new study will actually challenge the birds with thevirus after they have been vaccinated.

Independent efforts

Concurrently, researchers at CDC, in collaboration with Colorado StateUniversity, United States Army Medical Research Institute for InfectiousDiseases, Harvard University and Temple University, are investigating themanufacture of an oral vaccine for use on wild bird populations. Recentsuccesses with injectable vaccines may lead one step closer to this goal.

As for the vaccine available for use in horses, although zoo officialshave tested its efficacy on birds, by and large they report it appears tohave little effect, if any, on avian species, with the exception of flamingosand black-footed penguins, says Bright.

Disney Wildlife Conservation Fund is primarily funding the bird vaccineproject. Additional supporters include the Dallas Zoo, Brookfield Zoo, FranklinPark Zoo, Houston Zoo and St. Louis Zoo.