May 25, 2010
The Unleading of a Swan
A long road back to recovery
Roberto Aguilar, DVM
The male mute swan came to the Cape Wildlife Center in Barnstable, Mass., on a bitter cold day last December. He had been rescued in nearby Plymouth by an Animal Control officer, who came across the anemic and underweight bird being chased by another swan.
Weakness prevented him from raising raise his wings off the ground or lifting his head, which he rested on his neck. He acted starved in spite of having food in his crop, a sack-like pouch that grain eating birds fill to digest later.
When we first examined him, we were at a loss of what could cause these clinical signs. Blood tests revealed the problem: he had a very high level of lead in his system – nearly enough to kill him. He probably ingested the lead from an old lead fishing sinker lying on the bottom of a waterway. Lead sinkers are banned, but still persist in the environment.
The lead in his system was chronically poisoning the swan. We immediately started chelation therapy with Calcium EDTA, an agent that binds to lead and helps eliminate it. It was less expensive than some alternative forms of therapy, and less invasive since it can be given orally. Most lead elimination methods require multiple injections.
The twenty rounds of chelation – five days on and two days off, took almost four months and cost roughly $1,500. Eventually, the signs of poisoning disappeared and the swan started moving around and eating normally.
Lead in the Environment
As this case shows, lead poisoning is a serious problem for wildlife. Lead is a basic element that doesn’t rust or change. Once in the environment, lead remains there for centuries. It poisons the animals that ingest it, as well as animals farther up the food chain.
Lead has affected some species severely. In the case of the California Condor, it has compromised the reintroduction of the species back to the wild. The effort has literally cost millions of dollars. Some evidence suggests that lead may have been a factor in the near disappearance of the California condor in the first place.
Bald eagles, mourning doves, geese and numerous waterfowl are severely affected when they ingest lead particles. Loons may have been wiped out from parts of the Northeast by ingesting lead in fishing tackle. The fact that once in the environment it stays there unchanged makes its effect on wildlife in general even worse.
Dr. Aguilar is veterinarian at the Cape Wildlife Center.