An interesting article from National Geographic highlights a surprising yet substantial source of demand for shark products: the manufacture of vaccines, in particular those used against swine flu. Shark livers have high concentrations of an organic compound called squalene, which happens to be an effective immunologic adjuvant. Adjuvants stimulate the immune system to increase the response to a vaccine, meaning that less of the vaccine’s active component is required in order for it to prove effective. Consequently the use of adjuvants is recommended by the World Health Organisation, and they are primarily harvested from commercially fished shark species, including those listed as vulnerable to extinction by the IUCN Red List.
One pharmaceutical company (GlaxoSmithKline) has taken orders for 440 million doses of the swine flu vaccine, which is estimated to require in excess of 4 tonnes of shark liver oil. A GSK spokesperson revealed that the company accounts for approximately 10% of their supplier’s total output, emphasising the considerable quantities of shark liver oil being traded and devastating impact this could be having on shark populations. Squalene tends to be predominantly sourced from deepwater sharks via bottom trawling, which itself is a highly destructive fishing practice. As with most sharks, deepwater sharks tend to be slow maturing and produce few young infrequently, making them susceptible to dramatic population declines from only moderate fishing pressure.
There are alternatives to shark-derived squalene, however, which can be extracted from vegetable sources instead, including olive oil. Whilst many cosmetic companies have switched to using plant-derived squalene, there is not yet a viable shark-squalene alternative for the manufacture of adjuvants, according to GSK.
The use of shark squalene as an immunologic adjuvant is another example of how shark species can benefit human health as well as the balanced functionality of marine ecosystems, but further highlights the urgent need for shark populations to be managed sustainably: their overexploitation to meet high demand can lead to irreversible population declines that in turn may severely detriment human health.