Herd immunity in the wild

The shot. The jab. The vax. Whatever you call it, Canadians are rolling up their sleeves to get immunized against the COVID-19 virus. When my turn came, I happily endured the drive to the vaccination centre, the wait in line, and the imperceptible prick of the needle in my upper arm. Heck, I even curated a vaccine playlist to keep me occupied through the process. (Playlists are a thing, really.). Pat Benatar’s “Hit me with your best shot” was at the top of mine.

Aside from my natural fascination with the role science has played in the rapid development of vaccines to help combat this deadly illness, there is a reason why I—a waterfowl and wetland scientist—am writing this column about it. Sea ducks. That’s right. If you can’t make the connection, bear with me. It’s pretty cool stuff.

The vaccine is providing hope that at some point soon, enough of us will be protected from the COVID-19 virus to slow its transmission among the world’s human population: a condition known as herd immunity.

And sea ducks? Let’s look northwards to find interesting parallels to our own pandemic predicament.

In January 2021, a group of waterfowl researchers published an article in Scientific Reports, titled Herd immunity drives the epidemic fadeout of avian cholera in Arctic-nesting seabirds.  Their research focused on northern common eiders (Somateria mollissima borealis) breeding at the largest colony in the Canadian Arctic, on Mitivik Island, Nunavut.

Eiders are highly gregarious sea ducks and are susceptible to one of the most significant and deadly infectious diseases affecting North America’s wild waterfowl: avian cholera. According to the article’s authors, this disease “is spread directly via bird-to-bird contact, environmentally through ingestion or inhalation of aerosolized bacteria in contaminated food and water, and through scavenging of infected carcasses.”

Apart from the carcass scavenging, is any of this starting to sound familiar?

What the researchers found in the case of the Mitivik Island colony, was that herd immunity was instrumental in stopping avian cholera from destroying their population. Between 2005 and 2012, avian cholera had a devastating effect on the colony, reducing eider breeding density at Mitivik Island by more than 50 per cent. Over time, however, death rates dropped from 36 per cent among breeding common eider females to almost none by 2012. How? Herd immunity was achieved when birds developed antibodies, similar to how humans develop antibodies through natural exposure—or more quickly through stronger immune response to vaccination.

Beyond the striking parallels between human epidemiology and duck population ecology, I believe we can take heart from this study for several reasons. First, the ducks were able to adapt to a seriously deadly curve ball. Second, there is a DUC connection. One of the study’s authors, Jane Harms, is a past recipient of an Institute for Wetland and Waterfowl Research Fellowship, which enabled her to conduct this research. Investments in wetland and waterfowl science, through fellowships like ours and our new Endowed Chair at the University of Saskatchewan, continue to prove their relevance to Canadians in myriad ways. Hope for the future is one of them.

So, when it’s time for the medical pros to administer your vaccine, roll up your sleeve and think about that colony of eiders, now happily breeding in the remote Canadian Arctic after achieving herd immunity.

And let them hit you with their best shot.

Stay well,

Dave

David Howerter is DUC’s chief conservation officer. His column, Big Idea with Dr. Dave, appears in every issue of Conservator magazine, where he explores the intersection of waterfowl and wetland science with current events.