FCUSA BACKGROUNDER, OCTOBER 2010

Canaries in the Food Chain: Food-borne illnesses in mink herds

Mink eat what we eat.

As carnivores, mink are exposed, through the feed products they consume, to every toxin in the human food production chain. But, unlike humans who generally cook their food, therefore killing any pathogen, mink feed is usually served up fresh and raw. And since mink herds are closed and isolated, the toxin in the cycle stops at the mink herd.

Mink act as canaries in the food chain, a definite plus if one is looking for pathogens in our food supply.

Over fifty years, mink herds have exhibited symptoms when exposed to salmonella, BSE ("mad cow"), even influenza in swine herds (H3N2).

The good news is that such outbreaks in mink herds due to toxins in the food chain are exceedingly rare. A report on H3N2 in Canadian mink considered this so rare, the authors commented, "The natural occurrence of influenza virus infection in mink with the presence of clinical signs is a rare event that deserves to be reported."(1)

As for BSE, which exhibits in mink as transmissible mink encephalopathy (TME), it is so rare that there is not a single living veterinarian who has ever seen a case. But veterinarians noticing the syndrome in the 1980s were on the front lines of recommending changes in US feeding practices that made the food chain even safer for humans and mink alike! Mink are now being used as an important model for studying the agent that causes BSE.

Mink are highly susceptible to anything amiss in the food chain and are, therefore, a perfect choice for laboratory work on toxins.

In fact, it was this sensitivity to toxins that first alerted humans to the negative impacts of PCB pollution in the Great Lakes. Farm-raised mink were the first to exhibit reproductive symptoms after eating PCB-contaminated fish.

Domesticated herds of mink are practical sentinel models for the food chain, a line of defense that tells us when something is amiss in the food on which we all depend. So a big thank you to our North American mink, the canaries in the food chain!

NOTES:

(1) Characterization of a Canadian mink H3N2 influenza A virus isolate genetically related to triple reassortant swine influenza virus. C.A. Gagnon, G. Spearman, A. Hamel, D.L. Godson, A. Fortin, G. Fontaine, and D. Tremblay, Journal of Clinical Microbiology, 47(3): 796-799, March 2009.

Further reading:

PUBLICATION:  The Guardian (Charlottetown)
DATE:  2010.10.02
SECTION:  Editorial
PAGE:  A14
COLUMN:  Letters to the editor

NO FOUNDATION TO THESE FEARS

Editor:

Sharon Labchuk, leader of the Green Party of P.E.I., raises public health fears that may be useful for scoring political points but are without any real scientific foundation ("Many questions about mink farm", The Guardian, Sept. 24, 2010).

In fact, Influenza A infections in commercial mink are rare and there is no evidence that any strain of influenza A virus has become specifically adapted to mink or that mink are a reservoir for influenza viruses.

So at this point using influenza as an argument to prevent the establishment of a new mink farm has no scientific validity and is being used entirely as a scare tactic.

If indeed this argument were valid then it could be used as the basis against establishing poultry farms, swine farms, running horse stables, establishing local zoos, promoting wild waterfowl parks etc.

Dr. Bruce Hunter,
Professor, Avian Pathology
Department of Pathobiology
Ontario Veterinary College
University of Guelph

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