Diclofenac levels in livestock carcasses in India before the 2006 ban

Three species of Gyps vulture, once common across the Indian subcontinent, have declined by more than 97% in India since 1992, and are now on the verge of global extinction. The decline is due to contamination of their food with diclofenac, a non-steroidal anti-inflammatory drug (NSAID) commonly used as a painkiller for livestock in India. On May 11, 2006, the Drug Controller General (India) ordered the withdrawal of all licences granted for the manufacture of diclofenac for veterinary use in India within three months. To monitor the effectiveness of this ban in protecting Gyps vultures it is vital to verify levels of diclofenac in livestock carcasses in India both before and after the ban, to determine whether diclofenac use is being reduced. In this study, we collected liver tissue samples from 1,848 livestock carcasses at 63 carcass dumps and four slaughterhouses across 12 Indian states during the period May 2004 to June 2005. The diclofenac levels were quantified using liquid chromatography-electrospray ionization mass spectrometry, with a limit of quantification (LOQ) of 10 µg/kg and limit of detection (LOD) of 4 µg/kg. Across the 12 states, diclofenac residues were found in 10.1% of livestock carcasses sampled: a prevalence of contamination more than sufficient to cause widespread mortality of vultures. There were significant differences in the prevalence of diclofenac between states and sites, and between the species and age-classes of animals, with cattle having a higher prevalence of diclofenac than any other species, and with higher levels of contamination in female animals. In addition, our sampling revealed differences in the daily intake rate of carcasses between sites, with an overall average of 7.47 ±0.58 animals per day across the 63 carcass dumps, and a maximum of 50 animals per day at Ludhiana (Punjab). Despite the large number of carcasses available, Gyps vultures were only sighted for three days out of the total 169 days of survey time spent at carcass dumps. The large number of carcasses and low numbers of vultures demonstrate that food availability is not an important factor affecting vulture populations in India. Repeated surveys, following the methods detailed in this study, are now vital to monitor and assess the impact of diclofenac levels in livestock carcasses available to vultures.