Spiralling out

by human activity is easily understood, though difficult to halt: the spectacular decline in once-common species that ranged over vast areas of diverse habitats proved initially a much more difficult problem to understand. An example of this is the extraordinary reduction in numbers of three Asian vultures — the Oriental white-backed (Gyps bengalensis), long-billed (Gyps indicus) and slender-billed (Gyps tenuirostris) vultures — to less than five per cent of their population numbers of less than 15 years ago. Researchers have been working full speed to try to understand the reason for this population collapse and studies suggest that it results from the use of diclofenac, a non-steroidal anti-inflammatory drug (NSAID) now used widely in the treatment of domestic livestock. Vultures are exposed to the drug when they consume the carcasses of animals that were treated with diclofenac shortly before death. Vultures die from kidney failure within days of exposure to diclofenac-contaminated tissues, with post-mortem findings also showing extensive visceral gout. Although the drug has been linked to the decline of three species of Asian vultures, diclofenac, as well as other NSAIDs, may pose a danger to a further five other Gyps vultures found in Asia, Europe and Africa. A new study by an international group of scientists led by Gerry Swan at the University of Pretoria, South Africa, reporting in Biology Letters of the Royal Society (published online), has looked at the toxicity of diclofenac to G. africanus and G. fulvus, a eurasian species, both of which are still abundant relatives of the endangered Asian species. The study demonstrated that diclofenac was highly toxic to both of these species, and therefore these species are as sensitive to the drug as their endangered relatives. The researchers found that the pathology following exposure to the drug showed similar problems with the kidneys and gout as in their relatives. Determining the toxicity of diclofenac and other NSAIDs to vultures and other scavenging birds is an urgent priority, the authors write. " A better understanding of the exposure of scavenging birds to NSAIDs and knowledge on the mechanism of the NSAID toxicity are urgently needed to enable a better assessment of the likely current and future impact of these drugs. " In the short term, the abundant G. africanus may be a useful surrogate to establish the safety of other NSAIDs to the endangered species, they write. Three species of once-common vultures in Asia …