While antimicrobials are essential and effective tools for use in humans and animals, antimicrobial resistance (AMR) is a growing global concern which puts at risk the prevention and treatments of bacterial infections. Increasingly, consumers are concerned about the transmission of resistant bacteria from animals and food that is derived from those animals.

Addressing those concerns, the potential impact of the treatment of mastitis with antimicrobials is being evaluated by industry, regulators and academics alike. These are their views.

The industry view
While the industry has clearly defined responsibilities when it comes to bringing veterinary medicines to market, it is in the best interest of all stakeholders that practices are identified, communicated and implemented, said Tony Simon, director, European Scientific Affairs at Zoetis. He told this to the 650 or so attendees at this year’s National Mastitis Council (NMC) regional meeting held in Ghent, Belgium.

“Here the industry can help play an important role in the debate around benefits, risks and responsible use,” he said.

Before they can be approved for use, he continued, veterinary antibiotics must meet very high standards with regards to safety, quality and efficacy. Safety assessments evaluate toxicology, target animal safety, user safety, maximum residue limits, residues and withdrawal periods, and environmental risks.

When it comes to quality, not only does the finished product need to be proven, consistent quality of both the raw materials and the manufacturing process itself must also be proven. Furthermore, in order to substantiate claims about effectiveness, marketing authorization holders must demonstrate that the product is indeed effective in preventing or treating the medical condition through detailed field trials.

“The reason for using antibiotics in bovine mastitis is either to treat clinical or subclinical infections in lactating cows, or at drying off to treat a cow subclinically infected and to prevent infection during the dry period,” Simon said. “The benefits need to be balanced against the risks and costs.”

In order to mitigate the risk of antimicrobial resistance, Simon emphasized the importance of responsible use. Responsible use includes minimizing unnecessary treatment while providing effective treatment when needed.

The academic view
During the first decade of the 21st century, sales of antimicrobials for veterinary use increased in the Netherlands; however, consumption of antimicrobials by the Dutch is among the lowest in Europe. In 2010, the emergence of antimicrobial resistance in livestock led the Dutch government to demand a decrease in the use of veterinary antimicrobials.

Their goal was to reduce usage by 50 percent of 2009’s numbers by 2013. Besides the enforced reduction, the Health Council of the Netherlands also advised the limitation of specific antimicrobials, including fluoroquinolones and third-generation and fourth-generation cephalosporins, in order to preserve them for human use.

In order to meet those goals, an independent institution, the Netherlands Veterinary Medicines Authority, was formed. Their role was to create transparency and to set benchmark indicators for antimicrobial use in livestock production.

Tine van Werven from the Faculty of Veterinary Medicine, Utrecht, presented the results from the dairy industry, with special emphasis on the prevention and cure of mastitis, at this year’s NMC regional meeting.

Although the total use of antimicrobials in dairy was relatively low in comparison to other livestock species, their use could still be decreased. Of the 18,053 dairy farms evaluated in the Netherlands, approximately 50 percent of total antimicrobial use was applied for dry cow treatment.

Another 23 percent was applied for the treatment of subclinical mastitis. Approximately 5 percent was used for parenteral treatment attributable to mastitis, which makes the overall total usage of antimicrobials for mastitis about 70 to 75 percent.

Thanks to new measures, the Netherlands was able to lower those numbers significantly, though. Full transparency of antimicrobial consumption was obtained, and a total of 57 percent was achieved.

“In spite of an initial low consumption of antimicrobials in dairy herds, since most of the treatments are on an individual cow level, a reduction of approximately 30 percent was achieved in 2013,” van Werven said. Most of that reduction was achieved by implementing selective dry cow treatment, although the total effects of their implementation won’t be known until next year.

“The question of further reduction of the use of antimicrobials should not be achieved by a further reduction of the use or misuse of antibiotics but by more sound management and a well-balanced nutrition,” van Werven concluded.

The regulator’s view
“Some 25,000 people die in the EU from an infection caused by multi-drug-resistant bacteria,” said Jordi Torren Edo from the European Medicines Agency in the U.K. “Antimicrobial resistance puts at risk the effective prevention and treatment of an increasing range of infections caused by bacteria in man and animals.”

Torren Edo was one of three panelists to speak about AMR at this year’s NMC regional meeting. All of this is taken into account when regulations are made, he said, but the reality is that we don’t know if there is transfer of resistance.

While resistance from human use is likely, resistance from animal use is not, but there’s always the possibility. In any event, regulators make recommendations to establish priorities and to reduce consumption.

Antimicrobials are strictly regulated in the European Union (EU). A maximum residue assessment is conducted to evaluate consumer safety, said Torren Edo. As is the quality, safety and efficacy of the intended medicinal product. Furthermore, the use of antimicrobials as growth promoters is banned in the EU.

On top of that, the European Surveillance of Veterinary Antimicrobial Consumption (ESVAC) collects harmonized sales of antimicrobials for vet use. In 2009, only eight EU countries collected data. By 2012, that number had risen to 20 countries. Today, 26 of 29 countries provide data for ESVAC.

At the end of his talk, Torren Edo did note that intramammary products represent less than 1 percent of total antimicrobials sold in the EU. Furthermore, he said, waste milk that might contain residues is not sold or fed to cattle, although it should be noted that with respect to the potential impact on AMR, the significance of feeding calves with waste milk has not been established. PD

Melanie Epp is a freelance farm writer from Guelph, Ontario.