Blue-green algae have been associated with a diarrheal disease which may affect travelers.
The person usually has had exposure to a contaminated water source. Evidence of an algal bloom may be absent.
Clinical features:
(1) diarrhea which may start as explosive and watery and which may be prolonged (up to 7 weeks)
(2) anorexia
(3) fatigue
The algae can be demonstrated in the stool as:
(1) nonrefractile hyaline cysts measuring 8-9 microns I diameter
(2) red or pink spheres on a modified acid-fast stain
(3) bright blue circles under ultraviolet light (autofluorescence)
Algae can be isolated from stool but may require light exposure (1,280 lux from fluorescent lamps).
Exclusions:
(1) other enteric pathogens (norovirus, leptospirosis, Salmonella, Shigella, Vibrio, Giardia, etc)
(2) cyanobacterial toxins
