Sea lions suffering from neurotoxic poisoning usually show no interest in their young, and even attack them when they try to suckle. Photograph by Rick Loomis

California sea lions have been stranding with increasing signs of seizures due to domoic acid (DA) poisoning. Pregnant females are commonly affected and frequently lose their young after exposure to this harmful algal neurotoxin. Juveniles exhibit an epileptic disease state, even in the absence of the causative diatom Pseudo-nitzchia. Rodent models have established that low-level exposure to DA during pregnancy has greater health consequences for the fetus than the mother and causes long-term developmental effects to memory and learning.

A recent investigation by NCCOS researchers published in the March issue of Toxicology examined the maternal-fetal transfer of DA. Nearly one third of the toxin in the mother reached the fetus, but the fetus retained the toxin in the aminotic fluid, whereas the mother quickly eliminated the toxin. These first ever prenatal toxicokinetic parameters of DA in fetal animals suggest that fetal recirculation of DA via swallowing of the amniotic fluid sustains fetal brain concentrations at a relatively constant level over 24 hours. This increases their exposure time to the toxin at the target organ.

Like other such rehabilitation centers in California, the Marine Mammal Care Center in San Pedro is frequently overrun by sea lions with domoic acid poisoning. Photograph by Rick Loomis

These data are vital for determining the potential long term health impacts of prenatal exposure to this harmful algal toxin, particularly in marine mammal populations susceptible to DA poisoning. This research provides a basis for understanding why a short term poisoning that most commonly effects pregnant California sea lions results in long term disease in younger animals.

Publication: In Utero Domoic Acid Toxicity: A Fetal Basis to Adult Disease in the California Sea Lion (Zalophus californianus)

News feed: NOAA Researchers Establish Link between Epilepsy and Fetal Exposure to Algal Toxin in Marine Mammals