Ecology and Management of Avian Botulism on the Canadian Prairies

139used, as would be more appropriate for assessing field poisoning. Konst et al. (1965) suggestedthat the toxic oral dose <strong>of</strong> microcystin in mice is ~40x larger than the intraperitoneal dose. Fromthe trial, we know that 100 µg/kg is not toxic for mallards by the intraperitoneal route,suggesting that the oral dose would be >4,000µg/kg. A dose <strong>of</strong> that size would cost aboutC$2,400 for a single adult mallard.Another approach to resolve the toxicity <strong>of</strong> algal blooms for ducks would be to collect <strong>and</strong>preserve large amounts <strong>of</strong> suspected toxic algal material from the field, in an area where ducksare dying. The material could be tested for toxicity in mice first. If toxicity is detected usingmice, then it could be tested for toxicity in ducks by oral dosing. If it proved to be toxic, thetoxin(s) present could then be identified by laboratory analysis. A potential problem with thistechnique is that a mixture <strong>of</strong> toxins will likely be present, so it will be difficult to establishwhich toxins are important.The toxicity <strong>of</strong> algae to ducks could also be resolved with laboratory isolations <strong>of</strong> algal toxinsfrom cultures <strong>and</strong> further bioassays. A significant advantage <strong>of</strong> this approach is that experimentscan be repeated with changing variables to resolve the details <strong>of</strong> the pathology. Field trialswould be difficult to replicate <strong>and</strong> may not be effective in determining whether other,unmeasured toxins are influencing results. In addition, field trials cannot resolve complexitiessuch as synergism or bioavailability. Ideally, both field <strong>and</strong> laboratory approaches shouldbe used.