When the European Union (EU) passed legislation allowing veterinarians to prescribe diclofenac, Irene Bueno-Padilla became worried about the Iberian Peninsula, which stretches across Spain and Portugal. She has spent the last three years researching diclofenac’s effects on vulture populations in Spain and working with veterinarians in the country to mitigate the drug’s use.

Diclofenac is a nonsteroidal anti-inflammatory drug (NSAID) used in veterinary medicine to treat various types of inflammation. It’s also known to cause harm to vulture populations who become exposed to it through the carrion they consume.

“Vultures are an efficient way of cleaning the environment,” says Bueno, DVM, MPH, PhD, postdoctoral associate in the University of Minnesota College of Veterinary Medicine (CVM) Department of Veterinary and Biomedical Sciences. Vultures digest bacteria from carrion before it can spread to an ecosystem and cause harm. Bueno says that when vultures feed on carcasses contaminated with diclofenac, the birds can get visceral gout and die. “A very small amount of diclofenac can kill a vulture,” she says.

Four vulture species have been classified as “Near Threatened” or “Endangered” by the International Union for Conservation of Nature:

Photos by Miguel Carrasco

Learning from the past

Diclofenac began being used to treat inflammation in livestock in India in the 1990s. When cows die in India, they are either taken to carcass dumps or left at the edges of villages. Vultures throughout the country have relied on this source of food for a long time. When research on diclofenac’s effects on vultures was conducted in India, researchers modeled what a contamination rate of just 0.3–0.7 percent of cattle carcasses with lethal levels of diclofenac in India and Pakistan would do to the vulture population. They found that one contaminated cattle carcass out of between 130 and 760 could have caused the oriental white‐backed vulture to decline at a rate of about 50 percent in one year.

“Vultures are cleaners of the environment,” says Bueno. “In India, once they began to disappear, there were dead animals left to decay—their bacteria and viruses were not being removed. And other scavengers, such as feral dogs and rats, were interacting with the carrion. Around that time, the feral dog population went up, which was at least partially the cause of a rabies outbreak in humans.” What happened in India is just one example of how public health can be affected by an environmental problem. “Sometimes we wonder why it matters if a species disappears, but it has a cascade effect.”

The Iberian Peninsula, which has 95 percent of Europe’s vulture population and is a major migratory flyway for avian species, is under major threat by use of diclofenac. The drug was recently approved for use in horses, cattle, and swine by the EU. Its history of deteriorating the vulture population in India means a thorough analysis of its risks to the Iberian Peninsula is critical.

From Spain to Minnesota, and back again

Bueno came to the U of M from the University of Cordoba in Cordoba, Spain, where she earned her DVM in 2007. She did a two-year clinical internship at The Raptor Center (TRC) and then earned her MPH while completing a three-year veterinary residency at TRC. As she was concurrently working on her PhD with advisors Randy Singer, DVM, PhD, professor in the Department of Veterinary and Biomedical Sciences, and Dominic Travis, DVM, MS, associate professor in the Department of Veterinary Population Medicine, she helped TRC on a project studying diclofenac in veterinary use in the Iberian Peninsula. For this work, Bueno received an honorable mention in the poster competition at the CVM’s Research Day. She defended her PhD in October 2018 and now works as a postdoctoral associate with Singer.

Bueno collaborates with a team of researchers on a project on diclofenac, which is funded for three years by Morris Animal Foundation and led by a research group at the University of Barcelona in Spain. At a conference in 2014, shortly after the legislation was passed allowing diclofenac to be prescribed in the EU, Bueno crossed paths with Ignasi Marco, DVM, PhD, who later became the principal investigator on this project. His team does the fieldwork, which includes sampling carcasses and vultures that arrive at wildlife rehab centers throughout Spain.

“At the University of Minnesota, we are using the data they collected, along with data from surveys we have conducted, on veterinarians and people that work at the [vulture feeding stations] in Spain and Portugal to develop a risk assessment. Then, we can estimate the risk of exposure of diclofenac and other NSAIDs to vultures,” Bueno says. “We are in the process of analyzing the samples now.” The project could be finished as early as September.

Affecting change

“At the European level, they approved this drug, which means all of the EU has access to the drug—but each country has a different environment,” says Bueno. “So maybe there are some countries with no vultures where the use of diclofenac would be fine, but once its use is approved at the EU level, it’s hard for countries who, like Spain, have a big vulture population, to limit the use of diclofenac.” Unless Spain and Portugal can show an evident risk associated with diclofenac, the legislation cannot be undone. At the country level, Spain wants to distribute its own drugs and do its own country analysis on how this might affect ecosystems in Spain. This is where Bueno’s research is essential.

Once analyzed, data from this project can in turn be used to guide government and veterinary authorities in their drug management policies. “Through surveys we have conducted with veterinarians in Spain, we have learned that many vets have not received education on how drugs they might prescribe can have consequences to wildlife and the environment,” says Bueno. “This might be an avenue we can pursue to suggest outreach and education to professionals in Spain. I think it would be good to create a framework for them in the future.”

The final risk assessment, due in September, will give researchers the complete picture of the estimated risk in Spain. “We also want to eventually investigate other avian scavengers,” Bueno says. “Other raptors, such as the golden eagle or [Spanish] imperial eagle, could be affected in Spain as well.”

Being from Spain has added to Bueno’s passion for spreading the word to veterinarians that the drugs they prescribe to food production animals have an effect on surrounding ecosystems. “I grew up there—I am passionate about the raptors in Spain and their migration patterns.”