A New DDT? Antibiotics Accumulate in Vultures

Neo, is not, a vulture.  But red shouldered hawks, like her, suffered from DDT poisoning. 

File this under incredibly scary.  This is the first report I’ve seen of the kind.  Researchers with several institutions in Spain, including the Universidad de Castilla-La Mancha, published their recent work in PLOS One this past week. 

Their project looked at the current accumulation of antibiotics and their residues in wild nestlings from several native species of vulture: griffon, cinereous, and Egyptian.  The survey included antibiotics common to livestock raised in the region, including: amoxicillin, oxytetracycline, enrofloxacin, and ciprofloxacin. 

The researchers found high concentrations of the antibiotics in a surprisingly large percentage of nestlings.  Interestingly, all cinereous vultures found dead had the antibiotics enrofloxacin and ciprofloxacin in their liver samples.  The idea is that chronic exposure to the livestock antibiotics effects the normal functioning of the birds’ own immune system, leaving them open to bacterial and parasitic infection.

In 2004 a study found that diclofenac, an antibiotic banned from use in the EU, was tied to declines of vultures in Pakistan.  This new study pushes the frontier of antibiotic-wildlife interactions further by shedding light on commonly used (and approved) veterinary medications that are having a cumulative harmful effect on scavenger populations.  As the researchers said:

If antibiotics ingested with livestock carrion are clearly implicated in the decline of the vultures in central Spain then it should be considered a primary concern for conservation of their populations.

I’m curious to know if this accumulation of residues is happening in scavenger populations outside of Spain, say, here in the US.  Turkey vultures and black vultures are common sights in central Florida and cattle farms, while certainly smaller in number these days, dot the landscape.  The question is, are our vultures snacking on livestock carcasses and ingesting antibiotics along the way? 

As a last note of interest, New World and Old World vultures are not directly related.  It is currently believed that Old World (like the Spanish cinereous, Egyptian and griffon) vultures evolved from raptors while New World (turkey, black, King) vultures are thought to be descended from highly adapted herons and storks.  One can only hope that the difference between the two groups might have conferred our New World vultures with some ways of circumventing organ failure in the face of accumulating antibiotic loads.  That is.. if its happening. 

Still, I think its a good knock to the head to remember that while we often think we’ve learned so much since the days of DDT and crumbling raptor eggs, we still may have a very long way to go.