Fish can be contaminated withC. botulinum, particularly type E, from
the aquatic environment and uncooked fish products have been respon-
sible for several outbreaks of type E botulism.
Smoked fish consumed without reheating has generally been hot-
smoked so control ofC. botulinumdepends on microbial inactivation by
heat plus the inhibitory effects of salt, smoke constituents and surface
drying. With the advent of refrigeration, the severity of the salting and
smoking stages has been reduced in line with the perceived consumer
preference for a less strongly flavoured product. In the early 1960s, two
outbreaks of type E botulism in North America associated with vacuum-
packed, hot-smoked fish caused considerable alarm and led to Canada
banning the importation of all types of packaged fish. A similar outbreak
in Germany in 1970 was caused by smoked trout from a fish farm. At
first it was feared that vacuum packing, an emerging technology at that
time, was responsible by providing an anaerobic environment in which
C. botulinumcould flourish.
It transpired that the problem was compounded of several factors. The
salting and smoking treatments had been insufficient to eliminate
C. botulinum or inhibit its growth during storage. A minimum salt
concentration (in the water phase) of 3% and an internal temperature
not less than 63 1 C during smoking are recommended. The product had
also been subjected to severe temperature/time abuse allowingC. botulinum
to grow and produce toxin. The product should have been stored at
temperatures below 4 1 C. Finally, vacuum packing had improved the
product shelf-life by inhibiting the normal spoilage microflora of bacteria
and moulds which would have indicated that the product was inedible.
Fish products that are consumed raw after a fermentation process have
also caused occasional problems, for example I-sushi (see Chapter 9).
In 1986 in the Canadian Northwest Territories an outbreak of type
E botulism was recorded after consumption of a meal comprising raw
fish, seal meat and fermented seal flipper. The latter had been prepared by
packing the product in a plastic bucket, covering with seal fat and leaving
it outside the house to ferment. The process differed from normal in that
the product was stored for 7 days instead of the usual three and the
weather had been unseasonably warm. It was claimed that the seal flipper
had an unusual taste and subsequent investigation established the pres-
ence ofC. botulinumtype E in the product. In Europe, the Norwegian
fermented trout rak-orret has also been responsible for outbreaks of
botulism.
The long association of botulism with meat products in Europe has
already been noted and inadequate curing of meats still gives rise to
occasional problems in some European countries. Outbreaks of botulism
in the UK are relatively infrequent. The largest outbreak this century
occurred in 1989 when 27 people fell ill and one died. In this outbreak the
208 Bacterial Agents of Foodborne Illness