Microsporidia are a large diverse group of intracellular parasites now 
considered as fungi. They are particularly prevalent in fish and are recognized 
as important opportunistic parasites in humans. Although the mode of 
transmission of microsporidia has not been fully clarified, the consumption and 
manipulation of infected fish may be a risk factor for humans. Comparative 
analysis of rDNA sequence revealed that the microsporidians used in the present 
study had 99-100% identity with anglerfish microsporidians of the genus Spraguea 
and very low identity with microsporidians that infect humans. Microsporidian 
spores were exposed to different physical and chemical treatments: freezing at 
-20°C for 24-78 h, heating at 60°C for 5-15 min, microwaving at 700 W, 2.45 GHz 
for 15-60s, and treatment with ethanol at concentrations of between 1 and 70% 
for 15 min. The viability of the spores after each treatment was evaluated by 
two methods: a) haemocytometer counts, measuring the extrusion of the polar 
filament in control and treated spores, and b) a fluorometric method, testing 
the membrane integrity by propidium iodide exclusion. The results of both 
methods were concordant. Spores were inactivated by freezing at -20°C for more 
than 48 h, by heating to 60°C for 10 min and by microwaving at 750 W, for 20s. 
Exposure to 70% ethanol for 15 min also inactivated microsporidian spores. The 
results suggest that both freezing and heating are effective treatments for 
destroying microsporidian spores in European white anglerfish, and that 70% 
ethanol could be used by fish processors to disinfect their hands and the 
utensils used in processing fish. The fluorometric method can be used as an 
alternative to haemocytometer counts in disinfection studies aimed at 
establishing strategies for inactivating and reducing the viability and the 
potential infectivity of microsporidians present in fish or in the environment.