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California Sea Lions Seizures May Come From Fetal Domoic Acid Poisoning
June 9, 2008
 Scientists,
reporting in the current issue of the online journal Marine
Drugs, state that an increase of epileptic seizures
and behavioral abnormalities in California sea lions can result
from low-dose exposure to domoic acid as a fetus. The findings
follow an analysis earlier this year led by Frances Gulland
of the California Marine Mammal Center that showed this brain
disturbance to be a newly recognized chronic disease.
John
Ramsdell of NOAA's
Center for Environmental Health and Biomolecular Research
in Charleston, SC, in partnership with Tanja Zabka, a veterinary
pathologist at the Marine Mammal Center, conducted the first-of-its
kind analysis of poisoning by the algal toxin, domoic acid,
during fetal brain development. The results, analyzed across
multiple animal species, point to the toxin as a cause for
behavioral changes and epilepsy that does not become evident
until later in life.
Domoic
acid is produced by harmful algal blooms. The algae is consumed
by fish such as sardines, herring and anchovies, a significant
part of the sea lion diet. Exposure during
pregnancy concentrates the domoic acid toxin in the mother's
amniotic fluid, which normally protects and aids in the growth
of a fetus. In sea lions exposed to domoic acid, the fluid
retains the toxin, thus subjecting the fetus to repeated direct
absorption through immature skin cells and swallowing during
gestation.
The
results, demonstrated experimentally in laboratory animals
and projected to occur in fetal sea lions, is abnormal development
of brain neurons which does not impact the animal until it
enters later life stages. This phenomenon, known as "fetal
basis to adult disease," is expressed through seizures and
abnormal behavioral changes.
"This
represents a significant break through in understanding the
origins of this behavior and will help us better understand
the long-term consequences of exposure to harmful algal blooms
during pregnancy," notes Ramsdell.
Algal
blooms have been increasing in the sea lions' habitat, resulting
in more cases of acute poisoning and increased concern over
the long-term effects of algal toxins.
Scientists
in NOAA's Oceans and Human Health Initiative
are studying the impact of harmful algal blooms on marine
mammals to determine if similar impacts could affect humans
exposed to the similar harmful toxins.
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