8 Jan 2018
Tim Potter discusses the importance of cattle vaccines to reduce antibiotic use and the vet’s role in advising farmers.
Tim Potter
Job Title
This October saw the publication of the UK Veterinary Antibiotic Resistance and Sales Surveillance Report for 20161, which announced antibiotic use in food-producing animal species had decreased by 27% to 45mg/kg – two years ahead of the Government’s commitment to reduce antibiotic use in livestock and fish farmed for food to a multi-species average of 50mg/kg by 2018.
The report included the lowest UK veterinary antibiotic total sales figure recorded (337 tonnes) since regular UK antibiotic sales reporting began in 1993. This demonstrates the commitment of all sectors of UK agriculture to reduce the usage of antibiotics in livestock – but how do we build on this success and address the continued issue of antimicrobial resistance, while still ensuring highest standards of welfare and productivity on our farms?
Contrary to antibiotics, vaccines have the benefit of working with the animal’s immune system to enhance the natural ability to fight infections and, as such, represent a key tool for reducing the need for antibiotics. A study2 demonstrated that calves injected with a particular vaccine required 15% less antibiotics in the first 190 days of rearing than animals that had not been vaccinated.
Published in October last year The Targets Task Force Report 20173 highlighted the role vaccination has to play in reducing antimicrobial usage on farm. The report focuses on the role of vaccination in the control of bovine respiratory disease, a condition identified as one of the main reasons for antibiotic usage in the beef sector. The task force calls for engagement with industry stakeholders to monitor the use of vaccinations targeting respiratory disease in cattle, aiming for an increase year-on-year between 2017 and 2020.
In the UK, approximately 42 vaccines are registered for use in cattle, offering protection against a number of viral, bacterial, parasitic and fungal pathogens4. The uptake of these vaccines varies by product and indication, but previous work has shown 86% of cattle farmers use one or more vaccines on their farm5. Vets have a key role to play in the implementation of vaccine programmes on farm and, through interviews with farmers, a study6 identified five key themes that relate to how the role of the vet in vaccination was perceived by farmers (Panel 1).
These five points highlight the importance of vets throughout the farmer’s decision-making process on whether to vaccinate, as well as the implementation of the vaccination programme.
Developing an effective vaccination protocol for a herd can be one of the most challenging parts of farm animal practice, and often involves balancing a number of different animal, environmental and human factors. Vaccination programmes should be designed to provide the most effective immunity to animals prior to stress or exposure. Ultimately, no single correct programme exists – rather, the programme should be tailored to the individual farm based around its husbandry practices, disease status, management strategies and facilities, while also taking into account the disease risk and the cost-benefit analysis.
The five points identified by Richens et al6 describe an almost stepwise process to vaccination commonplace on most farms – in that a problem is identified, diagnosed and a vaccination plan is put in place to reduce the impact of the disease or prevent future incursions. This means it is not unusual for vaccine programmes to change over time to take into account new and emerging diseases, and, as part of the health planning process, it is important things are regularly reviewed to ensure continued efficacy.
On individual farms, pathogens will exist that are considered endemic or always potentially present and able to produce disease, and, for these, vaccination should always be recommended. However, for other pathogens the risk may change over time, due to changes in circumstances (eradication programmes, changes in management or geographical spread); therefore, for these, it is important to regularly review the need for vaccination within an individual farm system.
In herd-based systems the main goal of vaccination is to increase immunity in the group, rather than the individual, and it is important herd immunity is considered as an indicator of the efficacy of the vaccination programme. This is especially important when it comes to managing clients’ expectations of vaccines. Take respiratory vaccines – for example, farmers will often look for 100% protection and 100% reduction in clinical signs, which, given the multi-factorial nature of the disease, is unachievable. What is achievable are reductions in clinical signs, pathogen shedding and infection load at a group level. All of these things are desirable, and of benefit to animal health and welfare, and farm economics. It is just a case of ensuring we communicate well with our clients and manage expectations.
One area where vaccine programmes fail is when vaccinations are administered under conditions that do not allow ample opportunity for the development of an effective immune response. Management systems often do not allow for vaccinations to be administered prior to risk periods; the classic example will be cattle vaccinated for respiratory disease following movements between farms. In an ideal world, animals would have completed their vaccination programmes prior to movement, but this is not always possible.
Stressors, such as handling, dehorning, weaning, castration, diet changes, as well as changes in environment and social groups, can all have a negative impact on the development of an immune response post-vaccination. It is, therefore, important when working with clients on the implementation of effective vaccine programmes that instruction is given on when products should be administered relative to periods of stress.
Many opportunities can arise to undermine the efficacy of vaccination programmes. It is essential farmers follow the instructions provided by the manufacturer on how to store, prepare and administer the vaccine. It is worth bearing in mind label recommendations can change over time and, when reviewing vaccine programmes, it is a good idea to go through all the details of how to administer them to ensure everyone involved with the process is clear on exactly what to do. Panel 2 provides a summary of the key practices that can reduce the efficacy of a herd level vaccination programme.
Vaccine storage and handling is one area where improvements can easily be made. Manufacturers provide specific guidelines on how vaccines should be stored and strict controls exist on this up to the point they are dispensed. Following this the responsibility lies with the farmer on how they are transported and stored.
Williams and Paixao7 examined how effective farm fridges were at maintaining vaccines at correct temperatures. Out of the 19 fridges surveyed, none succeeded in maintaining the correct temperature for 100% of the time and a significant proportion were outside of the correct temperature range for long enough to result in a loss of vaccine potency. Failure to maintain correct storage temperature has been shown to compromise vaccine efficacy.
Live vaccines are more sensitive to potency loss at elevated temperatures, while inactivated vaccines are typically more stable to moderate heat exposure, but more sensitive to freezing. When we dispense vaccines, it is important clients are given correct instruction on how to transport and store them to ensure their investment is not compromised.
With continued concern over antimicrobial resistance, vaccines have a key role to play in the management of animal disease. We are privileged in the UK to have a number of efficacious products at our disposal, but it is important we work with our clients to ensure we get the most out of them.
A number of potential areas exist where vaccine programmes can fall down, but, through regular review and planning, and by proper client education, it is possible to avoid these and implement effective bespoke vaccination programmes on farm.
