Investigation of the toxicology and public health aspects of the marine cyanobacterium, Lyngbya majuscula

Osborne, Nicholas John Thomas (2004). Investigation of the toxicology and public health aspects of the marine cyanobacterium, Lyngbya majuscula PhD Thesis, School of Population Health, The University of Queensland. doi:10.14264/uql.2015.210

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Author Osborne, Nicholas John Thomas
Thesis Title Investigation of the toxicology and public health aspects of the marine cyanobacterium, Lyngbya majuscula
School, Centre or Institute School of Population Health
Institution The University of Queensland
DOI 10.14264/uql.2015.210
Publication date 2004
Thesis type PhD Thesis
Open Access Status Other
Supervisor Glen Shaw
Penny Webb
Total pages 246
Collection year 2004
Language eng
Subjects L
321299 Public Health and Health Services not elsewhere classified
730210 Environmental health
Formatted abstract

Lyngbya majuscula is a filamentous marine cyanobacterium with a worldwide distribution in temperate and tropical regions to a depth of 30m. Over 70 chemicals have been isolated and characterised from this organism, many of which are biologically active. Dramatic responses have been elicited after human exposure to lyngbyatoxin A (LA) and debromoaplysiatoxin (DAT), toxins extracted from L. majuscula. These chemicals have been found to cause irritation at concentrations as low as 100 pmol and exposure of humans to this cyanobacterium in the enviroimient is associated with irritant contact dermatitis, as well as eye and respiratory irritation. Previously, L. majuscula has been reported as implicated in negative health outcomes only in Hawaii and Okinawa. Recently large blooms of L. majuscula have occurred with increasing repetition in the Moreton Bay region as well as other areas along the eastern Australian coastline. A broad study of this organism and its potential effect on human health was undertaken. 

LA and DAT and were found in samples of L. majuscula collected from Eastern Moreton Bay and North Deception Bay, Queensland, Australia, respectively. Samples of L. majuscula obtained from West Maui, Hawaii and the freshwater L. wollei from Florida contained LA. A quantitative measure of the irritant effects of the chemicals found in L. majuscula was made using a mouse ear-swelling test. The relative toxicities of two purified toxins, LA and DAT, were examined. These were found to produce swelling to a similar extent. The time course of inflammation and histopathological results were also similar for the two purified toxins. Less than 1 μg per ear of either toxin or a mixture (1:1) of the two toxins caused a measurable increase in ear thickness. When toxins were combined (1:1) there was an additive, not synergistic effect. Increases in ear thickness occurred within 15 minutes. Crude extracts of L. majuscula from Moreton Bay were also applied to mice ears. The effect of crude extracts from Eastern Moreton Bay were not fully explained by the measured LA content, suggesting other toxin(s) and/or modulating factors were present. This effect was not found with L. majuscula containing DAT from North Deception Bay. Some samples of L. majuscula containing no measurable quantities of LA or DAT were found to exert an inflammatory response. This response had a different time course to response to LA or DAT. 

In an effort to understand the potential exposure of humans to the toxins of L. majuscula the spatial and temporal distribution of LA and DAT were made in Eastern Moreton Bay and Northern Deception Bay. Not all samples of L. majuscula contained LA or DAT. More than ten-fold differences in DAT concentration were found at a single time at North Deception Bay (0.93-11.17 mg/kg freeze dry weight). LA was predominantly found at Eastern Moreton Bay while DAT was found only at North Deception Bay. Highest concentrations of toxin occurred when bloom size and density were also at their maximum (131.9 mg/kg LA and 43.0 mg/kg DAT). In an attempt to predict where L. majuscula biomass and toxins were maximal, and hence greatest chance of human exposure, a variety of physical and biotic parameters were obtained. Bloom intensity occurred when water temperature was maximal. Low precipitation periods were noted to occur before blooms. Total and dissolved reactive phosphorus were present at bloom initiation and peaks of chlorophyll-a in the water column were found at the peaks of L. majuscula bloom intensity. 

In an attempt to understand the extent of human exposure to the toxic effects of L. majuscula several epidemiological studies were completed. To assess the potential affects a survey of the health of ocean users in the North Deception Bay area, a residential area close to L. majuscula blooms, was undertaken. A postal survey was mailed to 5000 residents and a response rate of 27.4% was achieved. High numbers of people (78.2%) responding to the survey reported marine recreational water activity in Moreton Bay. Of those having marine recreational water activity, 34.6% reported at least one symptom, with skin itching the most reported symptom (22.7%) while fever was the least (0.4%). Younger participants had greater water exposure and symptoms than older participants. Participants with greater exposures were more likely to have skin and eye symptoms, suggesting agents in the marine environment contributing to symptoms. Of those entering Moreton Bay waters 29 (2.7%) reported severe skin symptoms, 12 of who attended health professionals. Six (0.6%) reported the classic symptoms of recreational water exposure to L. majuscula, severe skin symptoms in the inguinal region. Participants with knowledge of L. majuscula reported less skin, gastrointestinal and fever and headache symptoms. 

Anecdotal evidence reported an outbreak of symptoms similar to those expected with exposure to L. majuscula on Fraser Island during the late 1990s. Examination of first aid records from Fraser Island revealed an outbreak of symptoms in January and February 1998. This coincided with the presence of a bloom of L. majuscula. The other four years examined had no L. majuscula blooms and the number of Z. majuscula symptoms was much reduced. 

Keyword Cyanobacterial toxins
Public health
Additional Notes Variant title: Toxicology and public health aspects of Lyngbya majuscula.

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Created: Fri, 24 Aug 2007, 18:35:53 EST