Autopsies on two of the greyhounds at Wonderland found the dogs died of pneumonia, a complication that can be caused by infection by either bacteria or a virus.

Dr. Lisa Zerbel, a veterinarian in Massachusetts who is treating some of the sick dogs, said she thinks the illnesses are caused by a new strain of the influenza virus that is more virulent than the common one known as "kennel cough." But other experts say it is too soon to pinpoint the cause.

Wonderland Greyhound Park, in this blue-collar city north of Boston, has been the hardest hit. Since May 4, 16 of its dogs have died from the influenza-like illness, and the track has suspended racing indefinitely and quarantined its 1,200 greyhounds.

Racetracks in Colorado, Iowa and Rhode Island have also reported greyhound deaths over the past month, while other states are seeing a rash of nonfatal cases, according to Massachusetts officials.

"The reason this is happening is because greyhounds travel from track to track, and they may be incubating the illness without someone knowing," Zerbel said.

Autopsies on two of the greyhounds at Wonderland found the dogs died of pneumonia, a complication that can be caused by infection by either bacteria or a virus.

"The most frustrating thing about it so far is it tends to be very silent early on," Zerbel said. "It's not until the late stages that they start to show signs indicating that they need treatment." By then, she said, a sick greyhound may be racing at a track in another state.

Gary Guccione, secretary and treasurer of the National Greyhound Association in Abilene, Kan., said similar outbreaks have plagued racetracks for the past three years.

"A major outbreak like this used to happen once every six or seven years," he said. "Now it seems to be coming on with more frequency and with greater strength. We're in desperate need of a good vaccine."

There is already a vaccine for kennel cough, but the Massachusetts State Racing Commission does not require it, and it is unlikely it would be effective in this case, said Dr. Alexandra Lightbown, the commission's chief veterinarian. In the meantime, all greyhounds at Wonderland are being treated with antibiotics as a preventive measure.

Virginia Tech's Dr. Brad Fenwick, a specialist in greyhound medicine, is leading the search for a new vaccine. He hopes to conduct experiments on a vaccine this summer. Track owners around the country are funding his research.

He said he doubts the deaths at Wonderland and other tracks are from a new strain of influenza. But he said it is not clear yet whether the infections are caused by bacteria or by a virus.

Bacterial pneumonia can result from a variety of illnesses, and in greyhounds it can progress from mild to life-threatening in a matter of hours.

At Dairyland Greyhound Park in Kenosha, Wis., roughly one-quarter of the track's greyhounds have become ill in recent weeks, though none have died, said Scott Larrivee, a spokesman for state regulators. Dairyland suspended racing this week.

Several greyhounds have died at Bluffs Run racetrack in Council Bluffs, Iowa, according to Sally Prickett, a state veterinarian. She is awaiting lab results.

She said kennel cough usually hits younger dogs because their immune systems are weaker. But this disease is striking older dogs, and appears more serious, she said.

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© 2005 Daily News Central. All rights reserved.