Early Type E Botulism Activity

Caspian TernType E Botulism, which has become a more or less annual event on the lower Great Lakes, causing significant avian mortality in most years, is a condition whose prevalence tends to begin late in the summer and peak during the autumn months when large numbers of fish-eating migratory birds are present. However, it is not uncommon for cases to occur sporadically earlier in the summer.

This year, we have had one confirmed case of Type E Botulism, in a Caspian Tern collected alive and sick near Burlington, at the western end of Lake Ontario, on 23 July. Serum collected from this bird tested positive for the presence of Type E botulinum toxin.
Early summer cases often involve scavenging birds such as gulls, but this tern had been consuming live fish. The ecological circumstances under which toxin is produced and made available through the food chain to birds are complex and remain poorly understood. Therefore, it is difficult to predict, from one year to the next, whether botulism will be a major problem or not.

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