Avian botulism has killed 67 endangered birds at Kanaha Pond Wildlife Sanctuary in Kahului in a week and a half, and the epidemic continues to rage, state Department of Land and Natural Resources officials said Friday.
A total of 74 Hawaiian stilts, coots and ducks have been afflicted with the paralytic disease - which is the same bacteria but a different strain as the human form associated with improperly canned food.
"People cannot catch avian botulism," assured state Forestry and Wildlife Division wildlife biologist Fern Duvall on Friday.
A Hawaiian stilt wades through murky Kanaha Pond on Friday. An outbreak of avian botulism at the pond has left more than 70 endangered Hawaiian stilts, coots and ducks afflicted with the disease, most of which have died. State wildlife officials are trying to stem the outbreak by removing carcasses and sick birds and controlling the water level.
The Maui News / MATTHEW THAYER photo
Some of those birds have been treated with an antitoxin, and a few have recovered enough to be released in other wetland areas, he said.
But numbers of carcasses pulled out of the pond each day - three to five - is "really frustrating," Duvall said, noting that he and his crew have been at the pond several hours every day since he detected the first afflicted bird June 12.
On Friday, he put the total count of birds with the disease at 41 stilts, 23 ducks and 10 coots - and 31 eggs abandoned by ill or dead parents.
"Every bird counts," he said. "That's a lot of endangered birds . . . a lot of death. It will take a long time to recoup that number."
This is the worst outbreak of avian botulism since 1999, when more than a hundred birds were afflicted at the pond, said Duvall. Statewide, there was an outbreak of the disease in Hanalei, Kauai, that killed 300 birds from December to March.
"In waterfowl, it is one of the most significant causes of death," said Thierry Work of the U.S. Geological Survey National Wildlife Health Research Center on Oahu, who performed the necropsy on the Kanaha birds and confirmed the outbreak.
Although of a different strain than the human variety, the bacteria kills birds the same way it does humans, he said. The toxin in the bacteria has a paralytic effect, blocking the nerve endings. Birds die from respiratory arrest or are unable to hold up their necks, sometimes referred to as "limberneck," and drown in the water, he said.
No one is sure how the outbreak began in Kanaha Pond, said Duvall. Other wetland managers have been on "high alert" to make sure the disease has not spread; Duvall said he has heard no reports that it has.
Botulism is a natural toxin produced by a bacteria commonly found in soil. The avian strain thrives in low- or no-oxygen water conditions. The disease is transmitted through the food system to birds. Maggots, which concentrate the toxin, can provide a high dose of the disease when eaten by birds, a DLNR news release said.
The infected bird could have flown in from another wetland; Duvall noted that there was an outbreak in a Lanai wetland among some coots in February.
Humans also have contributed to the ferociousness of outbreaks of the disease, Duvall said. He explained that these endangered birds have been concentrated in fewer and smaller wetlands through the years. Kanaha Pond once stretched farther into Kahului, he noted.
Fewer birds would be affected if they were spread out over more and larger wetlands, he explained.
"The impact is great, because we have concentrated the birds artificially," said Duvall. "We are majorly on the hook."
Work explained that if caught early, the impact of avian botulism can be limited. At Kanaha, the disease spread too far, leaving wildlife officials "kinda fighting a rear-guard action," he said.
That means going to the pond every day and removing dead carcasses and afflicted birds to stem the spread of the disease. Wildlife officials have tried to raise the water level in the pond, which would be an effective countermeasure, according to Work, but that option can be employed only in limited fashion at Kanaha due to nesting birds.
The outbreak will be considered over when biologists go three days without finding carcasses, said Duvall.
"We haven't had a drop in numbers," he said, noting that Friday they pulled out two stilt and one coot carcass.
"It's carcasses, carcasses, carcasses, so there is no more transmission route," said Duvall. "It has been hellish trying to stop it."
Duvall said officials don't need volunteers; the pond poses some safety hazards, he explained. Residents can report deaths of waterfowl to the state Division of Forestry and Wildlife, and wetland managers need to be vigilant. The phone number on Maui to report dead birds is 984-8100.
* Lee Imada can be reached at firstname.lastname@example.org.