Susceptibility of coho salmon, Oncorhynchus kisutch (Walbaum), to different toxins of Clostridium botulinum

摘要

Coho salmon Oncorhynchus kisutch (Walbaum), held at 15degreesC were tested for their susceptibility to toxins of proteolytic and nonproteolytic Clostridium botulinum types A, B, C-1, C-2, D, E, F, and G administered by the oral and intraperitoneal (i.p.) routes. By the oral route, the fish were most susceptibile to type E neurotoxin, which was lethal at a dose equivalent to 90 mouse intraperitoneal minimum lethal doses (MLDs). The oral lethal dose increased to 2000 MLD for nonproteolytic and proteolytic type F neurotoxins, but the toxin types A, B, and C-1 were not lethal to fish at 2000 MLD and type D was not lethal at 20 000 MLD (highest titre tested). The fish were not susceptible to 200 MLD (the highest titres tested) of type G neurotoxin or C-2 cytotoxin. By the i.p. route, all of the toxins except type G were lethal to coho salmon. Type E neurotoxin was the most toxic at a level of one-half the mouse MLD. Coho salmon held at temperatures ranging from 1 to 20degreesC were sensitive to type E neurotoxin by both the oral and i.p. routes. As the temperature decreased the fish became more resistant to type E neurotoxin by the oral route, but the i.p. dose remained one-half the mouse MLD at all temperatures.