FARMINGTON -- The mystery surrounding the deaths of 20,000 eared grebes along the Great Salt Lake shoreline has Davis County Mosquito Abatement District officials concerned, as a test is being conducted to determine if it is an existing West Nile virus strain or a mutated strain that killed the birds.
Mosquito Abatement District Director Gary Hatch appeared before the Davis County Commission Tuesday expressing his concern.
Hatch said he is not certain what effect the grebes infected with the West Nile virus may have on next summer's mosquito season, but there is the possibility the district could be facing a new strain of the virus in its effort to protect the public through its abatement sprayings.
Testing has confirmed that more than 50 bald eagles died in Utah after scavenging on dead grebes that had the West Nile virus, the National Wildlife Health Center said.
Wildlife officials earlier confirmed the virus caused the eagle die-off that began Dec. 1 and speculated dead migrating aquatic birds such as grebes were the culprit.
Hatch said the eagles fed off the grebes because fish were unavailable in the area due to the late November freeze.
But now district officials are concerned about where the grebes initially contracted the virus, and how it spread so quickly among that bird population.
"We know what killed the eagles," Hatch said. "But what happened with the grebes is the concern."
Local officials suspect based on the evidence of positive test results that the grebes likely contacted the virus somewhere else along their migratory route.
There are roughly 1 to 2 million waterfowl that migrate through the Top of Utah, according to officials.
Davis County only had two positive tests for the West Nile virus in 2013, Hatch said, both those cases found in sentinel chicken flocks in West Point.
Weber County had one positive West Nile virus case reported, it involving a horse.
Trying to figure out what killed all the grebes remains a mystery, Hatch said, where he has never seen that many birds die from the West Nile virus all at one time.
"That is the question. How did this happen?" Hatch said.
There could be future implications with this much virus load, Hatch said.
And as a result, Hatch said, his office is working with a lot of other officials in trying to figure this out.
But in the meantime the county's mosquito abatements makes plans to spray, last year treating 4,939 acres of mosquito larva by air and 1,057 acres of it by ground.
Contact reporter Bryon Saxton at 801-625-4244 or email@example.com, or follow him on Twitter at @BryonSaxton.