What's killing the birds in Georgian Bay?

WASAGA BEACH, Ont. -- The beaches along scenic Georgian Bay are littered with thousands of dead birds – that Federal and provincial officials believe the cause of the death is a severe form of botulism, apparently from the birds eating dead fish.

To find out more about botulism, we spoke to Doug Campbell, a Pathologist with the Canadian Cooperative Wildlife Health Centre at the University of Guelph, about how the disease grows, affects birds and fish, and whether human populations have anything to worry about.   

Is botulism that is killing the birds and fish in Georgian Bay? 

No it’s not confirmed at this time but it’s strongly suspected.

Why is botulism suspected in this case?  

For a couple of reasons I guess. The first is that this botulism is a repeated event on the lower great lakes. At this time of year, since 1998, there is almost invariably been one or more botulism mortality events occurring. So the geographical location is new but the range of the species involved and the pattern of events, the timing of it, is fairly typical with what we’ve come to expect with botulism.  The other reason is that there is probably a shortage of other candidate explanations. I’ve had the opportunity to look at a few birds from this occurrence at Wasaga Beach over the last month because it has been sort of building a long period of time and so far we’ve not discovered any evidence of any other disease in these birds. With something like this we do try and make sure that we’re not missing something else rather than just assume it is botulism but the probability is that it will turn out to be Type E botulism.

So Georgian Bay is a new location? What could contribute to the botulism moving there?  

We first saw type E botulism here in Canada in 1998. The disease had previously occurred on the American side of the great lakes as far back, that we know of at least, in the early 1960s. Why the disease comes and goes isn’t really known because it was quite an important disease on Lake Michigan and the American side of Lake Huron and even up into superior into the 1960s and then completely disappeared for twenty years. And then it reappeared in Lake Michigan in the 1980s and again after that, it disappeared. As I said, we first saw it in south-eastern Lake Huron, down near the provincial park in 1998. Following that it moved eastward, south and eastward into Lake Erie and then eastward into Lake Ontario until it was seen down in the very eastern end of Lake Ontario.  On Lake Huron, we really hadn’t seen much north of Kincardine until just a couple of years ago and over the last couple of years, we’ve seen some cases up and over the tip of the Bruce peninsula. So this occurrence in Wasaga beach area, I guess you could say is a natural, a logical eastward extension of where we have seen it before.

What is it that drives the movement of Botulism? 

What drives that movement is very much open to question. Here in the last 10 or 12 years in which we’ve been commonly seeing the disease, there seems to be some connection between the zebra mussels which have spread to the lakes as and the fish called the round goby which has also spread and extended its range over that period of time. What the exact nature of that link isn’t really clear but many of the birds that we’ve examined over time have been eating one of those creatures. So they obviously are playing some role in the process.

How are the mussels moved from place to place? 

The mussels are essentially everywhere in the lower great lakes now. And yes, they were transported on boats and via a variety of other means, when they first arrived here. They say the botulism itself is quite mobile in that once it’s present in an area the creatures that live in that area will probably pick up spores and the spores will live harmlessly in their bodies. So for instance, you’re a gull and you’ve picked up botulism spores and you’ve got them in your body, wherever you go the spores will be there, and should you die, or when you die, then the potential exists for toxin to be produced in the carcass. So by that means alone, it probably is quite a mobile disease.

Is it possible to say that human involvement spread the disease?  

I don’t know if that would be exactly fair. I guess it’s probably fair to say that we’re involved in almost everything that goes on; there is no pristine natural system. I don’t think you sort of have to, invoke a lot of human activity to explain the patterns or to speculate about the patterns of botulism as it occurs in the lower great lakes.

How does the disease, botulism, form? 

Botulism as a disease is essentially a form of food poisoning. Whoever gets it, whether it be a fish or a bird, takes in the toxin preformed. The toxin has been formed somewhere else. So it’s somewhat different from other types of food poisoning in which the bacteria will grow in our body. So you need a source of toxin and the toxin is produced by this bacterium, which exists in two forms. As I said, there’s a spore form which is quite resistant to a lot of different environmental changes and that spore allows the bacterium to continue to exist through time, through various changes of temperature and humidity and whatever else. And it’s resistant, it’s waiting and resting for the right time and the right time for it comes when there is a complete lack of oxygen and then some rich, protein source to grow on. Like a carcass. And under those circumstances, it will start to reproduce itself and produce toxin. So then if another creature comes along and eats that carcass, it will get intoxicated and get the disease. If nobody eats it, then it just goes back into the spore form and there will be more spores in the environment. So there is spores everywhere and creatures pick them up with no ill effect. But it’s the toxin that kills. So when you look at botulism as a disease of birds, you have to look at where they likely acquired the toxin. For some species of birds, such as seagulls, and other various species of gulls we have on the great lakes, it’s pretty obvious, because they are real scavengers. So if you have a fish that’s washed up on the beach and there is toxin being produced in the fish and the gull eats the fish, it can get the toxin that way. So botulism is a food poisoning and you just have to try and look at what the different species eat to try and evaluate where they likely were poisoned.

Are people in danger at all?  

There is no significant risk to people. The question about people and safety typically centers around two things. One is the handling of carcasses because if you’ve got hundreds or thousands of carcasses on a beach, someone has to clean them up and there is a risk to doing that. And the answer is really no. other than that you would normally take whatever precautions you take in handling a carcass just because of any other bacteria or anything else that could possibly be there. So you wear gloves and handle and dispose of them properly and wash afterwards. That’s all that’s needed for that part of the story.

The other question that is a little bit more complicated to answer. People ask about the fish. Whether there is any risk involved in eating fish because fish can be intoxicated as well. The answer to that is that it is possible that you’ve, say you’re a commercial fisherman, or an angler, you’ve picked up a fish that is affected by botulism and has toxins circulating in it. The odds are and this is known from experimental work, that most of the toxin is going to be present in the viscera of the fish, or the intestines, the heart, lung, liver, which people generally don’t eat. And there will be very little in the muscle, if there is toxin present in the muscle. Yes, it would be a potential source of toxin for people, but only if you eat the fish without cooking it because the toxin is destroyed by eat and it doesn’t take a lot of heat – estimated to be something like 3 to 5 minutes at 80 degrees centigrade – and that will destroy the toxins. So if the fish is thoroughly cooked, even if it toxin happened to be present, it would no longer be potent.

 Are there any significant environmental problems with an outbreak of botulism? 

I guess that’s a somewhat difficult question to answer because environmental problems, could be a loaded term, but it’s a fairly broad term, I think the biggest concern that people have had about the recurrent botulism events is there potential effect upon a varied species of birds. Because the birds are so vulnerable to poisoning. We have species like the common loon, which is coming through on its migration southward, and they typically will raft up in large numbers on the lower great lakes and stay here and eat fish and fatten up before they head south. So it’s an important staging area for them. Since botulism has become a regular event they’ve become quite vulnerable to these large-scale die-offs and as they get poisoned and as the population of loons seems to be large and healthy, they are absorbing substantial losses each year from this poisoning.