Persistence of Clostridium botulinum neurotoxin type E in tissues from selected freshwater fish species:: Implications to public health

Rainbow trout (Oncorhynchus mykiss), round gobies (Neogobius melanostomas), yellow walleye (Stizostedion vitreum), and yellow perch (Perca flavescens) were given Clostridium botulinum neurotoxin type E (BoNT/E) at four doses (0, 800, 1,500, and 4,000 mouse lethal doses). BoNT/E was sought in the fish tissues at death or at the conclusion of the experiment (10 days after treatment). Fish were divided into a fillet (axial musculature) and a nonfillet sample before testing for BoNT/E toxicity with a mouse bioassay. BoNT/E was detected in all species. The percentage of positive BoNT samples ranged across the species and doses from 0 (trout, perch, and walleye) to 17% (round achy) in fillet tissues and from 0 (perch) to 92% (round goby) in nonfillet tissues. The lack of positive fillet samples in three key commercial fish species suggests that the public health implications of eating these fish are minimal. However, the presence of toxin in the nonfillet compartment of a high proportion of fish supports the hypothesis that live intoxicated fish are a vehicle for the transfer of BoNT/E to fish-eating birds, which are then in turn, intoxicated.