5.2.3 Diclofenac and Vultures
The veterinary use of the non-steroidal anti-inflammatory drug, diclofenac, was
found to be responsible for the decline in populations of three vulture species in
Asia (Oaks et al. 2004 ). The decline in the populations was caused by renal failure
and visceral gout which was attributed to the use of diclofenac in cattle. The decline
in vulture populations, arising from the use of diclofenac, is thought to have serious
implications for human health. As vultures are a keystone species, their population
decline has a range of ecological, socio-economic, cultural and human health
impacts.
For example, Markandya et al. ( 2008 ) reviewed the economic implications of the
human health impacts, with regard to the decline in vulture populations. Livestock
carcasses are the main food source for vultures but are also eaten by feral dogs. As
the vulture populations have declined, the dog populations have increased; dogs are
the main source of rabies in humans in India and so it is probable that the incidence
of rabies in humans, and hence mortality, has also increased. Markandya et al.
estimated that the decline in the numbers of vultures had likely caused many
thousand extra deaths in the human population although this has yet to be corro-
borated from health monitoring data.
5.3 Human Health Risks
As well as posing a risk to aquatic and terrestrial organisms, residues of veterinary
medicines in the environment may pose a risk to human health. Consumers might
be exposed to these veterinary medicines in several ways, via consumption of:
crops that have accumulated veterinary medicines from soils or as a result of
exposure to contaminated manure or slurry; animals that have accumulated veteri-
nary medicines through the food chain; fish exposed to treatments used in aquacul-
ture; abstracted groundwater and surface waters contaminated with veterinary
medicines. While veterinary medicines are routinely monitored in target food
materials, to ensure that concentrations are below the maximum residue levels
(MRLs) and hence protect human health, the magnitude of the exposure via all of
the routes listed above, has not been extensively investigated.
Hughes et al. ( 2006 ) used data on the human health hazard results, from food
intake surveys and modelled exposure concentrations to assess the potential risks to
consumers following indirect exposure for a selection of veterinary medicines.
The results of the risk assessment were generally reassuring, with the estimated
combined intake from plant-derived foodstuffs, drinking water and, where appro-
priate, farmed fish, amounting to less than 20% of the acceptable daily intake (ADI)
for each of the sections of the population considered for approximately two thirds of
the medicines selected for evaluation. A small number of substances (including
albendazole, deltamethrin, florfenicol, medroxyprogesterone, tylosin, dihydrostrep-
tomycin, salinomycin sodium, toltrazuril and nitroxinil) were identified as being of
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