Effective or Not? Has the Ban on Diclofenac to Save India’s Vultures Worked?

The results of a study published in 2011, five years after the ban in 2006, says yes, there has been a perceptible change in the use of diclofenac for veterinary use. But there is much more work to be done for the ban to be a success and for the country to see a rise in vulture populations.

The Indian subcontinent lost 95 per cent of its vultures in just 15 years. Of the eight species of vultures found in India, three – the oriental white-backed, long-billed vulture and slender-billed vulture – are listed as being threatened with extinction after rapid population declines began in the 1990s.

The Bombay Natural History Society (BNHS), and other reputed international organisations, traced the cause of this rapid decline to a veterinary drug called diclofenac. Diclofenac is a cheap anti-inflammatory drug used to treat livestock by thousands of cattle-herders.

The effects of diclofenac on four species of captive vultures were studied experimentally—death occurred within a few days and extensive kidney damage was observed in the animals post mortem. Similar results were seen in the majority of vulture carcasses collected from the wild since declines began.

The National Board for Wildlife in India, based on BNHS reports, recommended a ban on veterinary use of diclofenac on 17 March 2005. In May 2006, a directive from the Drug Controller General of India was circulated, requiring the withdrawal of manufacturing licences for veterinary formulations of diclofenac. This directive was further strengthened in 2008, when it was made an imprisonable offence to manufacture, retail or use diclofenac for veterinary purposes.

Objective of the Study

The main objective of the study was to estimate changes in the level of exposure of vultures to diclofenac over time.

Methods

Data were collected from three surveys carried out before and after the implementation of the ban on veterinary use of diclofenac. The first survey was in May 2004–July 2005, before the ban; the second in April–December 2006, immediately after the ban; the third in January 2007–December 2008, a few years after the ban came into effect. Liver samples were taken from a large number of sites distributed across the northern half of India, predominantly from carcasses of cattle and water buffalo, deposited at carcass dumps managed by local government corporations, co-operatives, private companies and individuals, and cattle welfare charities. Samples were also collected from slaughterhouses. Sampling locations were typical of sites formerly used by large numbers of foraging Gyps vultures.

Results

1. Before and just after the implementation of the ban, the proportion of samples with diclofenac were broadly similar. However, prevalence and concentration were both substantially lower in the third survey.
2. In 7–31 months after the first implementation of the ban, the prevalence and concentration of diclofenac in carcasses of domesticated ungulates available as food for vultures in India had decreased by about half. This is likely to be representative of the situation in north-western India as well.
3. Based on the data above, and the results of modelling the impact of this on vulture populations, the expected rate of decline of the Indian oriental white-backed vulture population has also been cut by more than half.
4. A recent estimate of the rate of decline in oriental white-backed vulture population in India, from road transect counts, shows an annual decline of 44 per cent per year between 2000 and 2007. After the ban, and the results of this study, the new estimated annual decline rate would be 18 per cent per year.
5. This remains a rapid rate of population decline compared with rates for most other threatened bird populations. In situ conservation measures such as nest protection and supplementary feeding currently being carried out by conservation organisations cannot supplement such a drastic decline.
6. There is a continued presence of diclofenac in many carcasses which indicates that the problem has not yet been overcome.
7. A very low proportion of carcasses are required to contain lethal levels of diclofenac in order to account for the rapid pre-ban population declines of Gyps vultures. This makes it necessary to remove nearly all diclofenac from the vulture food supply if populations are to recover.
8. Surveys of pharmacy shops in India confirm that, while diclofenac packaged and labelled for veterinary use was rarely offered for sale for use on livestock after the 2006 ban, human formulations of the drug were being sold widely for veterinary use. Holding stocks of human diclofenac is not an offence. This probably accounts for the continued contamination of ungulate carcasses that was observed in the study.
9. If the recovery of wild vulture populations is to be achieved, additional efforts are needed to complete the removal of diclofenac from their food supply and to prevent its replacement by other lethal non-steroid anti-inflammatory drugs (NSAIDs) such as ketoprofen. Further effort is needed to promote the use of the alternative veterinary NSAIDs that do not pose a risk to vultures. At present, the only veterinary NSAID used in India that is known to have low toxicity to vultures is meloxicam.

From Effectiveness of Action in India to Reduce Exposure of Gyps Vultures to the Toxic Veterinary Drug Diclofenac by R Cuthbert, MA Taggart, V Prakash, M Saini, D Swarup, et al. (2011). PLoS ONE 6(5): e19069. doi:10.1371/journal.pone.0019069. The document is available for free download on the PLoS ONE website here.