The World Health Organization (WHO) has named antimicrobial resistance (AMR) as one of our global crises of today. Antimicrobial resistance is one of the major global public health and development threats. In addition, drug-resistant infections impact the health of humans, animals and plants, reduce productivity on farms and threaten consumers’ trust in the food products farms produce.
Over the years, several action plans have been implemented to reduce antimicrobial use in both the animal and human sectors. Due to these frameworks, the average use of antimicrobials across the veterinary sector in Europe has decreased by 53 percent from 2011 to 2022 (EMA, 2022). So why is this topic still hot? Why is it still relevant for vets?
Antimicrobials – a wonder of the modern world
We need effective antimicrobials to effectively treat infections. Given a new generation of critical consumers, most of whom have been raised far from the world of livestock production, we must expect our treatment decisions to be questioned. So, the aim of our treatments should always be to use enough antibiotics to achieve effective treatment, but no more than is necessary. We should never use drugs to compensate for poor management or as a preventive measure. This is a part of our professional pledge and a part of our food producers’ “licence to produce”.
The aim of our treatments should always be to use enough antibiotics to achieve effective treatment, but no more than is necessary
We know we are on the right track, but we can do it better. With the right treatment decisions, we can further reduce the use of antibiotics by 50 percent or more (Svennesen et al., 2023).
Decisions that matter – to treat or not to treat?
In cattle, antibiotics are most frequently used for mastitis treatment (Svennesen et al., 2023); in Denmark, 59 percent of the antibiotics used in dairy cows were used for mastitis. There are several key on-farm decisions where we, as vets, may directly influence antimicrobial use. We can influence not only the prognosis and detection of disease but also a combination of other factors, such as farm and cow economy, the return to normal production, the likelihood of culling, etc. But we must remember that the threshold is different for different groups of animals.
Thus, the decision whether to treat animals should be based on the history of the animal, clinical findings, diagnostic results and prognosis. Together with the immediate response when an animal is sick, the vet must consider the matter of preventive measures. This includes management routines, staff, feeding, stress levels, movement of animals and buying in new animals or bringing together animals of different immunological status.
A deep dive into antimicrobials for mastitis treatment
Cows with mastitis are most effectively treated at the beginning of lactation (Wilm et al., 2024). Cows with a history of mastitis or a chronically high somatic cell count (SCC) or those that are far from calving have a poorer prognosis of returning to normal udder health. It is unlikely that a cow with a chronic mastitis infection will ever be cured. Therefore, instead of risking contamination of younger and more vital cows, the herd would be healthier if the infected individual is culled early, thereby reducing overall contamination levels and the need for recurrent treatment.
Dividing mastitis cases into three groups (Figure 1) will greatly increase the effect of treatment and the volume of antibiotics needed (Wilm et al., 2024):
- Mild cases – only see changes in the milk (flakes). No treatment, or non-steroidal anti-inflammatory drugs (NSAIDs) only
- Moderate cases – swelling of the udder and changes in milk present. Here, the treatment protocol is intramammary treatment and NSAIDs
- Severe cases – display abnormal behaviours, such as loss of appetite and fever on top of swelling of the udder and changes in milk. The treatment protocol is NSAIDs, intramammary treatment and parenteral treatment (with fluids)
Using a parenteral antibiotic treatment compared to an intramammary treatment increases the active daily dosage by 16 times (Svennesen and Kirkeby, 2024; Svennesen et al., 2023).
Using a parenteral antibiotic treatment compared to an intramammary treatment increases the active daily dosage by 16 times
Cure rates in Denmark are currently at an average of 76 percent when using intramammary treatment (Svennesen et al., 2023), compared to 83 percent when using a combination of intramammary and parenteral treatment. Through a non-inferiority study, a group of researchers found the beneficial effects of a lower daily antimicrobial usage (AMU) compensatory to the slightly lower treatment effect of the intramammary treatment compared to the combination treatment (Svennesen et al., 2023).
Selective dry cow therapy
The use of antibiotics for dry cow therapy can be markedly reduced by looking at selective dry cow therapy schemes rather than blanket treatments. Designating cows for dry cow therapy based on their history of SCC, clinical cases of mastitis and findings in milk samples will reduce the need for antibiotics.
Selection of cows for dry cow therapy should be based on:
- A clinical case of mastitis in the current lactation (non-chronic)
- Greater than 200,000 individual SCCs in two out of the last four tests
- Positive bacterial culture of a major pathogen (Staphylococcus aureus, Streptococcus dysgalactiae, Streptococcus agalacitae or Streptococcus uberis)
AMU affects us all
When we prescribe antibiotics to animals on our farms, we impact not only the farmer and ourselves but also consumers, the community and the local environment – this is the core idea of One Health. One Health refers to an integrated, unifying approach that aims to achieve optimal and sustainable health outcomes for people, animals and ecosystems. It recognises that the health of humans, domestic and wild animals, plants and the wider environment are closely linked and interdependent. The One Health approach to preventing and controlling AMR brings together stakeholders from relevant sectors to communicate and work together in the design, implementation and monitoring of programmes, policies, legislation and research to mitigate AMR and attain better health and economic outcomes for us all.
One Health refers to an integrated, unifying approach that aims to achieve optimal and sustainable health outcomes for people, animals and ecosystems
In Denmark, the Thinktank FREJ launched such a project: “From the farmer to parliament – AMU reductions in animal food production”. From all layers of the food value chain, FREJ partners were invited to share their perspectives of prevention, management, feeding and treatment. This resulted in the development of an online learning platform for young people in the cities and a catalogue of suggestions for vets, farmers, politicians and stakeholders throughout the profession (FREJ, 2024).
