Crows found dead at the Bluffton Schools Complex and nearby neighborhoods weren't drunk, but poisoned.
Results of toxicology tests conducted by Clemson University found the 23 birds died from a pesticide.
Earlier tests by the S.C. Department of Health and Environmental Control were negative for West Nile virus and eastern equine encephalitis. And a vet's original theory that they were drunk on fermented berries or fruit also proved to be incorrect.
"I'm trying to figure out who applied the pesticide and at what point," said Daniela Payne, investigator with the Department of Pesticide Regulation at Clemson University. The department regulates licensing, certification and product registration for proper use of pesticides and investigates alleged misuse.
Violations of the S.C. Pesticide Act range from suspension of a business license to fines as much as $1,000.
Payne said she could not disclose the name of the pesticide, only that it was an organophosphate.
"I don't think (people) should be concerned," she said. "This appears to be a one-time, isolated incident because no other deaths have been reported since. It could be accidental poisoning or deliberate. That's what I'm trying to investigate."
Organophosphate compounds have become widely used in agriculture, the home and garden, and vary widely in their toxicity levels, according to the U.S. Centers for Disease Control and Prevention.
In certain cases, the pesticide acts as a nerve agent. Dogs, cats and birds are particularly susceptible, said Dr. Ben Parker of Coastal Veterinary Clinic in Bluffton.
Parker had taken in some of he sick crows brought to his office by residents several weeks ago. He had theorized the birds were drunk, but said Tuesday there are farm fields a mile or two from the school complex.
"They could have ingested the pesticide and got the effects as they're flying over the school complex," Parker said.
But if that were the case, the conditions of the crows he watched over but did not treat, and later released, would have worsened, he said. At first, the birds were disoriented, weak and couldn't fly, Parker said.
"They may have ingested a sub-lethal dose of the organophosphate, but exposure usually requires some form of treatment, including atropine and other medications," he said.
The neurotoxin can cause diarrhea, vomiting, altered mental status, weakness, paralysis and respiratory arrest in children and adults who ingest, inhale or come into direct skin contact with the pesticide, according to the CDC.
"You would have to be playing with the liquid specifically or ingest a certain volume for it to be harmful," Parker said. "Most pesticide companies have moved to pyrethrins that are less toxic for mammals and birds and breakdown quicker in the environment. This was more prevalent say 10 years ago."
Beaufort County School District spokesman Jim Foster said the district uses a pesticide to eliminate fire ants, but it is not the one found in the dead crows.
A DHEC spokesman said Tuesday the department is no longer involved in the case.
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