Birds Beware: Several veterinary drugs may kill scavengers

Scavenging birds worldwide could be at risk of accidental poisoning from carcasses of livestock that farmers had dosed with certain anti-inflammatory drugs, according to a survey of veterinarian records.

SENSITIVE. The Harris’s hawk, native to the Americas, is one of the species whose members have died after veterinary treatment with anti-inflammatory drugs. IStockphoto

The work grows out of discoveries in the past 2 years that several Gyps vulture species have almost vanished from India and Pakistan because residues of the anti-inflammatory drug diclofenac in dead farm animals ruin the kidneys of the scavenger birds (SN: 2/4/06, p. 70: Available to subscribers at Bird-Safe Rx: Alternative drug won’t kill India’s vultures).

To estimate sensitivities to diclofenac and related drugs, researchers combed veterinary records around the globe for unexpected deaths of captive birds treated with nonsteroidal anti-inflammatory drugs (NSAIDs). Suspicious deaths turned up in 11 species, including 7 not closely related to the Asian vultures, says Richard Cuthbert of the Royal Society for the Protection of Birds in Sandy, England.

The study associated diclofenac with more than two dozen bird deaths and carprofen and flunixin with several deaths each, Cuthbert and his colleagues report in an analysis now online and in the Feb. 22, 2007 issue of Biology Letters.

Because birds scavenge dead farm animals, “any NSAID that is used without testing [on birds] is a real cause of concern,” Cuthbert says.

The survey team collected records of NSAID treatment for nearly 900 birds in 79 species, mostly scavengers. The researchers looked for fatalities in cases such as minor surgery, where “the bird shouldn’t have died,” says Cuthbert.

Out of 40 birds treated with carprofen, 5 died, as did 7 out of 24 treated with flunixin. Deaths of two other birds—a Eurasian black vulture, which was the only bird in the study treated with ibuprofen, and one of Africa’s lappet-faced vultures, the only bird that got phenylbutazone—caused the researchers to call for more investigation. In contrast, meloxicam seemed safe for birds.

The deaths documented in birds receiving carprofen and flunixin included three black vultures and a spoonbill from Eurasia, a Marabou stork from Africa, and, from the Americas, two Harris’s hawks, a red-legged seriema, and two northern saw-whet owls.

Cuthbert worries about vultures that dine where conservationists in Africa set out dead livestock. Vets there use several NSAIDs that the new study links to bird deaths.

The world presents a vast patchwork of NSAID usage. India and Nepal recently banned the importation and manufacture of diclofenac. However, vets in South America use it, notes one of the paper coauthors, captive-raptor specialist Jemima Parry-Jones of the National Aviary in Pittsburgh.

U.S. vets don’t administer diclofenac to any farm animals, says pathologist Carol U. Meteyer of the National Wildlife Health Center in Madison, Wis. She says that the center hasn’t noted fatal kidney damage in any scavenging birds. However, she welcomes the new report as a good indication that farm veterinarians need to be very careful about pharmaceuticals.

Susan Milius is the life sciences writer, covering organismal biology and evolution, and has a special passion for plants, fungi and invertebrates. She studied biology and English literature.