After 19 animals had been found dead, two of the carcasses were sent to University of California, Davis, for testing. The results came back May 11 and show the ducks are dying from an acute viral infection, most likely duck viral enteritis, a herpes virus infection.
Duck viral enteritis causes internal bleeding and severe diarrhea. It kills many infected birds but doesn’t affect people.
“It’s like HIV for birds. … It’s sad,” said Lori McGrath, a member of the Duck Squad, a loose-knit group of about four residents who feed and watch over the ducks.
UC Davis checked also for poisoning. Those tests came back negative.
Valerie Tobler founded the Duck Squad after moving to the neighborhood in 1989. When a duck has a fishhook in its mouth, she frees it. If one is hit by a car or has a broken leg, she cares for it. Tobler said it was heartbreaking to find the birds’ bodies or see them acting listless.
“The first was a female,” Tobler said. “I didn’t see any injuries to her. … I left her there and the next day, I found her dead.”
It’s possible DVE is spread by infected ducks that shed the virus in their excrement. The virus survives in water, particularly in stagnant or slow-moving waterways. Waterfowl ingest the virus through drinking or swimming in affected water or by eating contaminated food.
It’s estimated that 30 birds at Desert Shores have died from it. Deceased Muscovy ducks and a dead mallard were found on north and south Lake Madison and north Lake Jacqueline.
Peregrine Wolff, a veterinarian with the Nevada Department of Wildlife, said the number of ducks dying all at once usually points to botulism C. But the tests ruled that out.
DVE, also known as duck plague, usually occurs in clusters, she said. Wolff said the virus could have been introduced by a new bird, or it could have been in a dormant state and activated through the stress of the mating season. Muscovy ducks seem to be more highly susceptible to DVE, she said.
“There are going to be some that are probably immune and won’t die, but most are going to die, as we’ve already seen,” Wolff said. “In most instances, it occurs in captive populations of Moscovy ducks or other domestic ducks.”
The mortality rate will be about 60 percent before the infection is over, Wolff said. She told of an outbreak in 1973 at Lake Andes National Wildlife Refuge in South Dakota that had devastating results, killing off roughly 100,000 birds. Containing such an outbreak is nearly impossible, as birds can fly in and out at will.
Infected birds may show signs of DVE within three to seven days of being exposed. Indicators include listlessness, a loss of appetite, bloody discharge from the bill area and emitting watery diarrhea. On occasion, swollen eyelids and drooping wings are noted. Some ducks are found dead without exhibiting any signs.
Wolff said Desert Shores management told her they opted to “ride it out” and let nature take its course.
“There’s not much you can do if it’s not a closed facility,” Wolff said, adding that disposing of the carcasses would help keep it from spreading.
Although humans cannot contract DVE, they should wear latex gloves when disposing of a bird carcass, Wolff said. Dogs should be kept away from the dead birds, she added.
Normally, Tobler said, quite a few birds get hit by cars each year, but only a few get sick.
“But not like this; these ducks are pretty much on their last legs or they’re already dead,” she said.
Contact Jan Hogan at firstname.lastname@example.org or 702-387-2949.