Abstract
The purpose of this review was to provide an updated overview on the use of antimicrobial agents in livestock, the associated problems for humans and current knowledge on the effects of reducing resistance in the livestock reservoir on both human health and animal production. There is still limiting data on both use of antimicrobial agents, occurrence and spread of resistance as well as impact on human health. However, in recent years, emerging issues related to methicillin-resistant Staphylococcus aureus, Clostridium difficile, Escherichia coli and horizontally transferred genes indicates that the livestock reservoir has a more significant impact on human health than was estimated 10 years ago, where the focus was mainly on resistance in Campylobacter and Salmonella. Studies have indicated that there might only be a marginal if any benefit from the regular use of antibiotics and have shown that it is possible to substantially reduce the use of antimicrobial agents in livestock production without compromising animal welfare or health or production. In some cases, this should be done in combination with other measures such as biosecurity and use of vaccines. To enable better studies on both the global burden and the effect of interventions, there is a need for global harmonized integrated and continuous surveillance of antimicrobial usage and antimicrobial resistance, preferably associated with data on production and animal diseases to determine the positive and negative impact of reducing antimicrobial use in livestock.
Generated Summary
This review article provides an overview of the use of antimicrobial agents in livestock and examines the impact of reducing resistance in livestock reservoirs on both human and animal health. The study considers the impact of antimicrobial usage, interventions, and the way forward in addressing the challenges of antimicrobial resistance. The review covers various aspects, including the impact of interventions to limit antimicrobial resistance and the positive and negative consequences. The focus is on changing patterns of risks, effects of interventions, and the way forward. The methodology involves a review of the existing literature on antimicrobial usage, resistance, and interventions in livestock production. The scope encompasses the global burden of antimicrobial resistance, the effects of interventions, and the need for harmonized surveillance systems. The review also touches on the ethical and economic dimensions of antimicrobial usage and the importance of the livestock reservoir for human health.
Key Findings & Statistics
- In 1951, 110 tonnes of antimicrobials were produced for animal feed, while 580 tonnes were used for medical purposes.
- By 1978, these figures had increased to 5580 tonnes as feed additives and 6080 tonnes for medical use, reflecting a 50 and 10 times increase, respectively.
- In 2011, the total domestic usage in the USA was 13,542 tonnes, exceeding the combined animal and human usage of 1978.
- Total meat production in the USA in 2011 was 42,452,759,000 kg, resulting in approximately 319 mg of antibiotics per kg of produced meat. This is significantly higher than in any European country.
- For humans in the USA, 3290 tonnes of antibiotics were sold in 2011.
- In the 1990s, nearly two-thirds of all antibiotics imported into Australia were for use in animals.
- In 1997, the Netherlands had the lowest antimicrobial consumption for humans in Europe.
- In 1999, the European Medicines Agency estimated a mean consumption of 98 mg of antimicrobials per kg of meat and poultry produced in 15 European countries during 1997.
- In 2011, 25 member states of the European Union used a total of 8481 tonnes of antimicrobials.
- In Denmark, data on antimicrobial resistance among food animals began in 1995.
- In 1951, the total consumption of antimicrobial agents increased tremendously, where a total of 110 tonnes were produced for addition to animal feed and other application, whereas 580 tonnes were produced for medical use in humans and animals.
- In 1978, this had increased to 5580 tonnes as feed additives, and 6080 tonnes for medical use. Thus, a 50 and 10 times increase, respectively.
- In the USA, the total consumption of antimicrobial agents increased tremendously from 1950 to 1978.
- In 1978, this had increased to 5580 tonnes as feed additives, and 6080 tonnes for medical use. Thus, a 50 and 10 times increase, respectively.
- In 2010, in Denmark, the yellow card scheme was implemented, where a reduction in total consumption and the consumption in 2011 was 25% lower than in 2010.
Other Important Findings
- The introduction of antimicrobial agents in the 20th century has revolutionized medical practices, yet antimicrobial resistance poses a significant threat.
- The livestock reservoir has a notable impact on human health, and the focus is now shifting towards pathogens like MRSA, Clostridium difficile, and E. coli.
- There’s a need for global initiatives, control, and monitoring systems to contain antimicrobial resistance.
- The speed of emergence and spread of antimicrobial resistance is unparalleled, highlighting bacteria’s adaptive ability.
- Antimicrobials are used therapeutically, metaphylactically, prophylactically, and sometimes for growth promotion, each with distinct implications.
- The use of antimicrobials for growth promotion is highly debated, and evidence suggests that it may be over-estimated.
- The ethical dimension involves balancing the benefits of treatment with the risks of promoting resistance.
- The livestock reservoir is crucial for human health, with a complex interplay of resistance and transmission.
- Interventions to reduce resistance include limiting selection pressure and controlling the spread of resistant bacteria.
- Denmark’s experience with reducing antimicrobial use through various measures, including bans and the yellow card scheme, is discussed.
- The Dutch experience shows that surveillance and intervention can lead to decreased antibiotic consumption in livestock.
- Several options exist for reducing risks, however, are not all equally successful due to hindering by national or international legislation.
- The use of antimicrobial agents for food animals is associated with either very limited negative effects or possibly even positive effects for animal health and welfare as well as economy.
Limitations Noted in the Document
- The document acknowledges limitations in the availability of exact figures for worldwide antimicrobial usage.
- The analysis of the impact of interventions is often complex, and not always collected in a systematic way.
- Studies on the effects of interventions, particularly in real-life conditions, are limited.
- The difficulty in obtaining good information about the consumption of antimicrobial agents in human and veterinary medicine, as well as the amounts added to feed for growth-promoting purposes.
- Data collection prior to and following interventions is not always systematic.
- The study states that the impact of these restrictions has not been quantified and these restrictions have since been lifted.
- The importance of multiple routes, including environmental spread, trade with live animals, human vectors, etc., have not been quantified.
Conclusion
The reviewed document underscores the critical importance of addressing antimicrobial resistance in the livestock reservoir to protect human health. The widespread use of antimicrobials in food animal production, though historically beneficial, has led to a significant increase in resistance, posing substantial risks. The study emphasizes that the reduction in routine antimicrobial use is associated with either very limited negative effects or possibly even positive effects on animal health, welfare, and the economy. The study shows that the use of antimicrobials for growth promotion may be over-estimated. The document highlights the need for improved hygiene and control measures to mitigate infectious diseases. It also states that the use of antimicrobials in therapy requires clinical judgement and monitoring of the results. The document advocates for international collaboration, comprehensive surveillance programs, and continued research into innovative strategies to reduce antibiotic usage and the transmission of resistance. The insights shared show that reducing resistance is now more important than ever. The Dutch experience also indicates that surveillance and intervention are valuable. It is important that farmers have incentives for better animal health, and that they also get support for management in an attempt to remove the use of antimicrobials.