I have been discussing this off-line with Dr. Dale Hill, animal nutritionist.
He commented:

Years ago in grad school, I did a seminar presentation on “Iron, Infection and Fever”.  The short story is that most pathogenic organism have a rather high iron requirement.  The fever response and reduced food intake in humans and animals was one of Nature’s ways of reducing available iron to the pathogens.  This article is completely in line with what I found those many years ago regarding iron and infectious agents. The iron, copper, zinc cadmium interactions are well documented in production ag species (mammals).  Most of the metallothioneins are fairly similar in structure and function, so finding this in bees comes a no surprise.  Excess calcium will depress zinc and cadmium absorption, excess iron will depress zinc and copper absorption, excess copper will depress zinc and cadmium absorption, excess cadmium depress zinc, copper and probably iron absorption as well – many of these trace elements  share the same  mechanism of absorption or similar competing mechanisms of absorption.  There are so many mineral interactions that good mineral research requires radioactive tracer studies.  Not many researchers have this kind of budget to work with and most universities are not equipped nor have any interest in doing studies with isotopes.  It’s not very glamorous compared to DNA mapping and genomics, so govt funding is nearly zero.
My contribution is that in the 70s, I was studying trace inorganic elements and heavy metals, the availability, uptakes, and impact under EPA funding of studies of copper smelter pollutants with respect to bee kills.  
Richard Cronn, an Environmental Studies grad student at UM, showed that bees exposed to cadmium produce metallothioneins.  He actually injected a cadmium solution into bees, then looked at the chemical changes and effects.
What we saw in our smelter region studies was that the colonies that lost bees to metals' poisoning versus control bees from 'clean' areas could be predicted by unusually low amounts of certain critical chemicals like zinc. The most obvious was zinc depression, which made sense in the context of cadmium and competition for binding sites within the bee.This was especially striking to see - low zinc levels in an area heavily polluted by zinc from the smelter. 
I also remember reading lots of reports from Europe in areas with aluminum smelters that emit fluoride, that beekeepers routinely provided their bees with iron fortified water in an attempt to mitigate fluoride poisoning. 
Jerry 


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