Virginiamycin chemical review

In September 1999, the Joint Expert Advisory Committee on Antibiotic Resistance (JETACAR) recommended that the APVMA (then the NRA) review the use of virginiamycin in food-producing animals. The APVMA began a review of virginiamycin in July 2000.

The APVMA reviewed the use of virginiamycin in food-producing animals because of concerns that using virginiamycin for growth promotion could pose an undue risk to human health. Given the use patterns of virginiamycin in intensive animal farming practices in Australia, there were concerns about the spread of resistant animal bacteria to humans and the transfer of antibiotic-resistant genes from animal bacteria to human pathogens.

The basis of the JETACAR recommendation was its report, The use of antibiotics in food-producing animals: antibiotic-resistant bacteria in animals and humans. The report found evidence for the emergence of resistant bacteria in humans and animals following antibiotic use, the spread of resistant animal bacteria to humans, the transfer of antibiotic-resistance genes from animal bacteria to human pathogens, and resistant strains of animal bacteria causing human disease.

In April 2003, the APVMA released the Virginiamycin draft review report. The report proposed a number of changes to the use of products containing virginiamycin. Some of the key changes included:

• cancelling the registration of products intended only for growth promotion or improved feed conversion efficiency (or both) in pigs, poultry and turkeys
• varying the labels of veterinary products for sheep, cattle and chickens to include more specific instructions on the circumstances in which the products should be used, the times when they should be used, the duration of treatment and the frequency of treatment
• limiting use to single, defined-period treatments.

The APVMA proposed these changes after finding there was an unacceptable risk of antibiotic-resistant bacteria (E. faecium) occurring in cattle, pigs and poultry following the long-term use of virginiamycin.

There was also evidence that antibiotic-resistant E. faecium bacteria in animals could transfer their resistance to E. faecium bacteria in humans, given the use patterns of virginiamycin and intensive animal farming practices in Australia. Consequently, using virginiamycin might pose an undue risk to human health.

In November 2004, the APVMA released its decision on the review of virginiamycin.

In the final report, the APVMA recommended:

• cancelling the registration and label approvals of three products that had label claims relating to growth promotion, improved feed efficiency or both
• varying the conditions of label approval for the three products (the label claims of which were for the prevention of necrotic enteritis in broiler chickens and lactic acidosis in cattle and sheep) to:
  • include a maximum treatment period of 21 days in chickens and 28 days in cattle and sheep, and only one treatment in any 12-month period
  • delete all label claims, indications and use patterns that refer to growth promotion, improved feed conversion efficiency or both
  • include more specific instructions and restraints pertaining to their use for the prevention of lactic acidosis in sheep and cattle and necrotic enteritis in chickens.

The APVMA decided to vary the labels of Eskalin Feed Premix for Cattle (APVMA 46049), Eskalin Wettable Powder Spray-On Feed Premix (APVMA 49111) and Eskalin 500 Feed Premix (APVMA 51354) by imposing mandatory restrictions on off-label uses, limiting the duration of use of the products to 28 days, and limiting the number of re-treatments of virginiamycin in a 12-month period. In 2005, Phibro Animal Health, the registrant of the three affected products, applied to the Administrative Appeals Tribunal (AAT) for a review of APVMA's decision.

During the AAT proceedings, Phibro Animal Health and the APVMA agreed that virginiamycin could be used prudently. The AAT determined that the label changes set out above would not proceed. Instead, the labels would be varied to require that veterinarians prescribe the three Eskalin products in accordance with the Australian Veterinary Association’s (AVA) Code of Practice for Prescription and Use of Products which Contain Antimicrobial Agents. The code of practice contains specific guidelines for the use of products that contain virginiamycin.

Labels for products that contain virginiamycin now bear the following mandatory prudent use statements:

Prior to prescribing [Name of Product] investigate the use of non-antibiotic options. If virginiamycin is indicated and selected for use, prescription must be consistent with the AVA Code of Practice for Prescription and Use of Products which Contain Antimicrobial Agents. Dosage regimens should be designed for each situation with an appropriate duration and frequency to minimise treatment failure while minimising the emergence of antimicrobial resistance. Review farm records on the use of product containing virginiamycin to ensure compliance with prescribing instructions.

NOT TO BE USED FOR ANY PURPOSE, OR IN ANY MANNER, CONTRARY TO THIS LABEL.