Banned antibiotic in livestock feed should not be given to horses

27 February 2013

The Soil Association is calling on the government to prevent the use of an unapproved antibiotic in horses, due to concerns about human health, following the discovery of horse meat in the food system. The antibiotic was widely used in livestock feed until 1999, when it was banned due to fears that this would cause resistance to a related drug held in reserve for treating humans with life-threatening infections in hospitals [1]. 

The unlicensed antibiotic, virginiamycin, is the active ingredient of Founderguard, a horse feed additive, which has never been though full safety tests or approved for veterinary use in the UK [2]. Despite this, the government has been allowing vets to import virginiamycin from Australia since 2001. Recent figures are not available, but data obtained by the Soil Association in 2008 under a freedom of information request, shows that about 10 tonnes of Founderguard was being imported annually [3].

Virginiamycin is closely related to Synercid [4], an antibiotic, kept in reserve for cases of MRSA (and other infections) that fail to respond to vancomycin [5]. This is currently the most important antibiotic for treating life-threatening cases of MRSA [5].

Previously the government has agreed that the use of virginiamycin in horses could pose a risk to human health. In a statement last year the Veterinary Medicines Directorate (VMD) (which regulates veterinary drugs for the government) said, ‘there is no robust evidence to suggest that the continued use of virginiamycin will not pose a risk in terms of antimicrobial resistance developing’ [6]. Despite this, the government has no plans to stop the drug being imported before September 2014 [6].

Since 2005, the Soil Association has repeatedly raised concern over the use of virginiamycin in horse feed. [7] [8]. However, those concerns were based on the possible transfer of Synercid-resistant strains of MRSA from horses to their riders through direct contact, as horses given virginiamycin were not supposed to enter the food chain [9] [10] [11] . Recent revelations about the widespread abuse of the horse passport system, and the discovery of horse meat in the food system, have given this already concerning issue an added urgency.[12]

In a letter to the Professor Peter Borriello CEO of the VMD [11], Soil Association Policy Adviser, Richard Young said,
“Since the transfer of resistant bacteria from horses to humans on food is clearly also possible where horse meat is consumed, we feel that the VMD should revise its timetable and prohibit any future importation of virginiamycin with immediate effect.”

Mr Young also said that, the VMD should make
“strenuous efforts to ensure that none of the horses that continue to receive virginiamycin in feed while stocks are used up, are permitted to enter the food chain.”


[1] Virginiamycin was approved as an antibiotic growth promoter for pigs and chickens throughout the EU and in many other countries. Such antibiotics were never subjected to the safety checks required before antibiotic can be used by vets to treat disease.
[2] Founderguard is given to horses at possible risk of developing laminitis.. This is a painful condition, but it can be prevented in other ways. In its statement in 2012 (see note 5, below) the VMD says ‘there is no robust evidence that Founderguard prevents laminitis’ and, ‘this condition can be managed through animal husbandry and pasture management’.
[3] The Soil Association submitted a Freedom of Information request in 2005 to establish how much Founderguard was being imported. The VMD refused to release the information, citing commercial confidentiality. After a 3-year battle between the Information Commissioner on behalf of the Soil Association and the VMD the data was finally released in 2008.
[4] Synercid contains the two antibiotics quinupristin and dalfopristin which are both related to virginiamycin. These antibiotics are now classified by the World Health Organization (WHO) as critically important in human medicine because of their importance for treating very resistant MRSA (methicillin-resistant Staphylococcus aureus) and enterococcal infections.
[5] Gould F.K. et al., 2009. Guidelines (2008) for the prophylaxis and treatment of methicillin-resistant Staphylococcus aureus (MRSA) infections in the United Kingdom, Journal of Antimicrobial Chemotherapy, 63: 849-61,
[6] Veterinary Medicines Directorate, 2012. The VMD phases out the importation of Virginiamycin for veterinary use, Press Release,
[7] Nunan C., 2005. Letter to David Lewsey (VMD)
[8] Nunan C. and Young R., 2007. MRSA in farm animals and meat,
[9] This is particularly significant since a new livestock-associated strain of MRSA, called MRSA ST398, has emerged in some British horses in the past few years. Loeffler A. et al., 2009. First isolation of MRSA ST398 from UK animals: a new challenge for infection control teams?, The Journal of Hospital Infection, 72: 269-71,
[10] Rayner D., 2008. Freedom of Information Act – Founderguard, Letter from the VMD to Lord Peter Melchett (Soil Association)
[11] Young R., 2013. Letter to Peter Borriello (VMD)
[12] 'Shambolic' horse passport system opens door to fraud – NFU: Farmers Guardian ( 21 Feb)

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