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Clinical Trial
, 8 (12), e83406

Dietary BMAA Exposure in an Amyotrophic Lateral Sclerosis Cluster From Southern France

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Clinical Trial

Dietary BMAA Exposure in an Amyotrophic Lateral Sclerosis Cluster From Southern France

Estelle Masseret et al. PLoS One.


Background: Dietary exposure to the cyanotoxin BMAA is suspected to be the cause of amyotrophic lateral sclerosis in the Western Pacific Islands. In Europe and North America, this toxin has been identified in the marine environment of amyotrophic lateral sclerosis clusters but, to date, only few dietary exposures have been described.

Objectives: We aimed at identifying cluster(s) of amyotrophic lateral sclerosis in the Hérault district, a coastal district from Southern France, and to search, in the identified area(s), for the existence of a potential dietary source of BMAA.

Methods: A spatio-temporal cluster analysis was performed in the district, considering all incident amyotrophic lateral sclerosis cases identified from 1994 to 2009 by our expert center. We investigated the cluster area with serial collections of oysters and mussels that were subsequently analyzed blind for BMAA concentrations.

Results: We found one significant amyotrophic lateral sclerosis cluster (p = 0.0024), surrounding the Thau lagoon, the most important area of shellfish production and consumption along the French Mediterranean coast. BMAA was identified in mussels (1.8 µg/g to 6.0 µg/g) and oysters (0.6 µg/g to 1.6 µg/g). The highest concentrations of BMAA were measured during summer when the highest picocyanobacteria abundances were recorded.

Conclusions: While it is not possible to ascertain a direct link between shellfish consumption and the existence of this ALS cluster, these results add new data to the potential association of BMAA with sporadic amyotrophic lateral sclerosis, one of the most severe neurodegenerative disorder.

Conflict of interest statement

Competing Interests: The authors have declared that no competing interests exist.


Figure 1
Figure 1. Four spatial units with a significant SIR.
The Hérault district is a coastal area in the very southern France, surrounding the mediterranean sea. The four significant spatial units are featured in dark grey. Two spatial units, cluster 1 and 2, surround the Thau lagoon.
Figure 2
Figure 2. Spatio-temporal ALS cluster in the Hérault district.
This cluster (dark grey area) is composed of 26 townships and has been identified for the period between January 1992 and December 2009, with 68 ALS cases for 33.7 expected (SIR = 2.02, RR = 2.24, p = 0.0024).
Figure 3
Figure 3. SIR evolution in the Hérault district according to the distance from cluster 1.
Maximum SIR is noted in cluster 1 and decreases rapidly when increasing the distance from this epicentre. Significance is p = 0.025, Stone's test for raised incidence around locations. Type of boots: parametric. Model used when sampling: Poisson. Number of simulations: 999. Statistic: 2.19325.
Figure 4
Figure 4. Seasonal variations of the picophytoplankton community in Thau lagoon from March 2009 until February 2010.
Circles: picocyanobacteria; triangle: picoeukaryotes; black: inside the farming zone, open: outside the farming zone.

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Grant support

This work was supported by INSERM and Ifremer. The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.