Published Date: 2012-02-26 14:03:30
Subject: PRO/AH/EDR> Red tide, redhead ducks - USA: (TX)
Archive Number: 20120226.1053079
RED TIDE, REDHEAD DUCKS – USA: (TEXAS)
A ProMED-mail post
ProMED-mail is a program of the
International Society for Infectious Diseases
Date: Thu, 23 Feb 2012
Source: The Brownsville Herald [edited]
Fishermen working in South Padre Island recently saw five ducks fly directly into a building, killing themselves.
Another 120 dead ducks were found over the last six weeks.
The birds’ carcasses were sent to a lab in Corpus Christi where biologists found the tissue contained brevetoxin, a potent neurotoxin associated with red tides.
Island Coastal Resources Manager Reuben Treviño said since the onset of red tide in September and October , gulls and pelicans have died, but the death of redhead ducks is abnormal. It isn’t immediately clear how the waterfowl are contracting the brevetoxin, he said.
“Redhead ducks winter here because of the sea grass. It’s what they feed on,” Treviño said. “So our next step is to collect sea grass samples from around the bay to determine if they are getting sick through the food web.”
The dying ducks aren’t limited to waters near South Padre Island. The entire 367-mile Texas coast is affected and reports of birds dying span the length of it.
The dead ducks first began appearing at a pond in front of the Pearl South Padre Hotel, an area where the ducks rest after feeding.
When the waterfowl are poisoned they display erratic behavior, such as flying in circles or letting humans approach them. The birds have also reportedly flown into power lines.
“And we wondered, is that really the problem? The power lines have been there for 20 years and it has never been an issue before,” he said.
And that’s why Coastal Resources had the carcasses tested, which showed the elevated levels of brevetoxin.
In conjunction with AEP Texas and Time Warner Cable, the city of South Padre Island has installed safety markers on existing overhead lines that may be associated with the bird’s death.
If the brevetoxin is in the sea grasses, there’s nothing that can be done to remedy it except to wait as the brevetoxin will eventually work its way out of the food chain, Treviño said.
“It’s a natural process and that’s how things play out sometimes,” Treviño said. “It’s a matter of monitoring and being aware of the ecosystem so we have a better understanding of it, period.”
ProMED-mail from HealthMap Alerts
[Red tide or Harmful algal blooms (HABs) are events in which single-celled protists, dinoflagellates, proliferate rapidly and accumulate in the water column. These events are associated with wildlife mortalities, because under certain circumstances these organisms can produce potent toxins. Normally these toxins enter the food web when they are consumed by filter feeding animals, such as clams, oysters, mussels, in which the toxin bioaccumulate. That is why the disease is not usual in a duck that only eats sea grass. It would be interesting to check the gizzards of the dead ducks to examine what they have been eating, and the toxin concentration of it.
For a picture of a redhead duck go to http://en.wikipedia.org/wiki/File:RedHead.jpg. Portions of this comment were extracted from http://www.sciencedirect.com/science/article/pii/S1568988303000696. A map of the affected area can be accessed at http://healthmap.org/r/1Rsy Mod. PMB