Cyanobacteria produce many neurotoxins including beta-methylamino-L-alanine (BMAA) that has been liked to amyotrophic lateral sclerosis (ALS) and neurodegenerative disease. A number of ALS cases have been diagnosed among residents of Enfield, NH, a town encompassing a lake with a history of cyanobacteria algal blooms. To investigate an association between toxic cyanobacterial blooms in New Hampshire and development of ALS, we reviewed records from our institution and other community databases to obtain demographic information on patients diagnosed with ALS within New England. We identified nine ALS patients who lived near Lake Mascoma in Enfield, NH, an incidence of sporadic ALS that is 10 to 25 times the expected incidence of 2/100,000/year. We suggest that the high incidence of ALS in this potential cluster could be directly related to chronic exposure to cyanobacterial neurotoxins such as BMAA. Possible routes of toxin exposure include inhalation of aerosolized toxins, consuming fish, or ingestion of lake water. Further investigation, including analysis of brain tissue for cyanobacterial toxins, will be helpful to test for an association between BMAA and ALS.
Ten to sixteen Daphnia were placed in small vials filled with natural water from a lake and incubated for 0.5 to 2.0 h. The small (ca. 0.10 µ3) bacteria were counted on Nuclepore filters by an Acridine Orange direct count method with epifluorescence. Filtering rates were calculated from counts of bacteria before and after the incubations.
For D. pulex, D. middendorffiana, and D. longiremis the filtering rates ranged from 0.2 to 1.5 · ml animal−1 · h−1 depending on the size of the animal and temperature. Simultaneous comparisons with rates of filtering on larger yeast cells indicated that these bacteria were filtered at about 30% the rate for yeast.
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