Animal antibiotic sales down
Total sales of veterinary and horticultural antibiotics in New Zealand have decreased for a fifth year in a row, dropping by 23% in 2022.
New antibiotics were rapidly discovered which revolutionised the means by which infectious diseases were treated. Suddenly, common human infections became easily curable and outbreaks of infectious disease were readily controlled.
However, just a few years after the golden age of antibiotics, warning signs of developing resistance were observed. Just as Fleming had predicted, previously susceptible bacteria were developing drug resistance at an alarming speed.
Although the magnitude of this problem is still unclear, it is proposed that abuse and misuse of antibiotics is largely responsible for the development of resistance. In an effort to slow this phenomenon, in 1955 penicillin was no longer freely available to the public, in lozenges and creams, and instead became 'prescription only'.
In less than 100 years after antibiotic discovery, we now face a grim scenario in which most antimicrobials might no longer be effective. Human and veterinary medicine may once again enter an era where common bacterial infections could once again prove lethal.
What is antibiotic resistance?
Antibiotic resistance is the ability of bacteria to survive and multiply in the presence of an antibiotic agent that would normally inhibit or kill this species of bacteria.
Bacterial populations can quickly modify themselves to resist antibiotics and then pass these resistance traits to the next generation of bacteria.
Sharing of resistance genes with other types of bacteria has also been seen.
Antibiotic resistance is just one mechanism by which bacteria have adapted to survive and is nearly as old as the discovery of antibiotics themselves.
A worrying fact in the modern world is the rate at which antibiotic resistance often develops and how quickly it spreads across the globe and amongst different species of bacteria.
Worryingly, more bacteria have also developed multiple drug resistance which severely limits therapeutic options for infections in animals and people.
Antibiotics in food-animals
The use of antibiotics in animals closely parallels their discovery and usage in humans. In the 1940s, the first antibiotic was introduced into food animal medicine. Subsequently newer antibiotics were discovered and made available for food animal species and their use became widespread to treat a multitude of infectious diseases.
Antibiotic usage in food animals improves more than just animal wellbeing; it also has economic benefits for food animal producers along with a safer public health sector. However, unnecessary or wasteful use of antibiotics should be avoided when non-antibiotic solutions are readily available or when the use of antibiotics for a particular disease condition are clearly not effective.
Antibiotics may be used therapeutically in animals for treating specific bacterial diseases. They may also be used for non-therapeutic purposes such as prophylaxis and metaphylaxis.
Veterinarians often prescribe antibiotics to animals not currently ill with a particular disease, but at high risk of acquiring an infection. For example, an animal may be treated with antibiotics after having undergone surgery (prophylaxis) or herds may be given antibiotics if they are at risk of suffering an outbreak of infectious disease due to high risk of exposure to disease agents (metaphylaxis).
In the dairy industry, mass administration of antibiotics is often practiced during dry-cow therapy to help prevent mastitis or prior to transportation of livestock over large distances to help prevent respiratory disease.
Prophylactic or metaphylactic use of antibiotics can help control and prevent numerous animal diseases. However, this use of antibiotics should never be intended to replace the need for good management practices, given that the use of antibiotics will eventually lead to resistance.
How can we slow down antibiotic resistance?
Prudent or judicious use of antibiotics is "the optimal selection of drug, dose and duration of antibiotic treatment". Also, inappropriate and excessive treatments should be reduced to help slow the emergence of antimicrobial resistance.
In the dairy industry this means that veterinarians and dairy farmers have dual roles in protecting animals from pain and suffering, while safeguarding the interest of public health.
Guidelines for antibiotic usage onfarm should be developed with a veterinarian. Each farm will be different and it is important to review these guidelines frequently.
Good records are essential to help determine the pattern of antibiotic usage from season to season and from year to year. Record keeping also prevents antibiotic-treated animals from contributing to the human food-chain.
Improvement of farm hygiene practices and animal husbandry will help reduce the usage of antibiotics onfarm and it is important to report periods of increased antibiotic treatments to a veterinarian.
Only use antibiotics in dairy animals for the specific reason for which they have been prescribed, at the specific dose rate and for the specific duration of treatment.
If the effectiveness of an antibiotic has decreased over time, report this to your veterinarian immediately.
A holistic approach to disease prevention is required to support a sustainable farming system that does not rely solely on mass-medication with antibiotics. This is critical to the future of dairy farming, veterinary and human health.
The author acknowledges the 'Get Smart on the Farm' programme by Michigan State University, the University of Minnesota and the Centers for Disease Control and Prevention, USA.
• Gemma Chuck is a vet with The Vet Group, Victoria, Australia.
