Research article

Primary irritant and delayed-contact hypersensitivity reactions to the freshwater cyanobacterium Cylindrospermopsis raciborskii and its associated toxin cylindrospermopsin

Ian Stewart^1,2,3 , Alan A Seawright¹ , Philip J Schluter⁴ and Glen R Shaw^1,3,5

¹National Research Centre for Environmental Toxicology, University of Queensland, 39 Kessels Road, Coopers Plains, QLD 4108, Australia

²School of Population Health, University of Queensland, Herston Road, Herston, QLD 4006, Australia

³Cooperative Research Centre for Water Quality and Treatment, PMB 3, Salisbury, SA 5108, Australia

⁴Faculty of Health and Environmental Sciences, Auckland University of Technology, Private Bag 92006, Auckland 1020, New Zealand

⁵School of Public Health, Griffith University, University Drive, Meadowbrook, QLD 4131, Australia

author email corresponding author email

BMC Dermatology 2006, 6:5doi:10.1186/1471-5945-6-5

Published:	31 March 2006

Abstract

Background

Freshwater cyanobacteria are common inhabitants of recreational waterbodies throughout the world; some cyanobacteria can dominate the phytoplankton and form blooms, many of which are toxic. Numerous reports in the literature describe pruritic skin rashes after recreational or occupational exposure to cyanobacteria, but there has been little research conducted on the cutaneous effects of cyanobacteria. Using the mouse ear swelling test (MEST), we sought to determine whether three toxin-producing cyanobacteria isolates and the purified cyanotoxin cylindrospermopsin produced delayed-contact hypersensitivity reactions.

Methods

Between 8 and 10 female Balb/c mice in each experiment had test material applied to depilated abdominal skin during the induction phase and 10 or 11 control mice had vehicle only applied to abdominal skin. For challenge (day 10) and rechallenge (day 17), test material was applied to a randomly-allocated test ear; vehicle was applied to the other ear as a control. Ear thickness in anaesthetised mice was measured with a micrometer gauge at 24 and 48 hours after challenge and rechallenge. Ear swelling greater than 20% in one or more test mice is considered a positive response. Histopathology examination of ear tissues was conducted by independent examiners.

Results

Purified cylindrospermopsin (2 of 9 test mice vs. 0 of 5 control mice; p = 0.51) and the cylindrospermopsin-producing cyanobacterium C. raciborskii (8 of 10 test mice vs. 0 of 10 control mice; p = 0.001) were both shown to produce hypersensitivity reactions. Irritant reactions were seen on abdominal skin at induction. Two other toxic cyanobacteria (Microcystis aeruginosa and Anabaena circinalis) did not generate any responses using this model. Histopathology examinations to determine positive and negative reactions in ear tissues showed excellent agreement beyond chance between both examiners (κ = 0.83).

Conclusion

The irritant properties and cutaneous sensitising potential of cylindrospermopsin indicate that these toxicological endpoints should be considered by public health advisors and reservoir managers when setting guidelines for recreational exposure to cyanobacteria.