22 Sept 2021
With vaccines in the news due to the COVID-19 pandemic, and live ones for livestock now available, it could be an even easier sell to farmers, as the author explains.
Phillip Jones
Job Title
Image: © Halfpoint / Adobe Stock.
Over the past couple of decades, the focus of general farm veterinary practice has increasingly shifted from call-outs to treat sick livestock towards vets working consultatively with farm clients to prevent disease and improve productivity.
Vaccines have been a critical part of this change – especially as the drive to reduce antibiotic use in the farming industry has surged in response to increased awareness about antimicrobial resistance.
Despite this, it can be a challenge to convince farmers that vaccinating their animals will be worthwhile. Time, labour and money constraints commonly deter farm clients from vaccinating, as well as the perception that a disease is simply not a problem on their farm.
The latest generation of vaccines – live vaccines – are accelerating the adoption of a preventive approach, as some of the typical barriers can be overcome, or at least outweighed, by other benefits.
Vaccines provide a small amount of disease-triggering material to the animal you are trying to protect, without causing disease in the recipient. Historically, this involved taking a dead or inactivated version of the virus or bacteria, and mixing with a storage solution to produce a vaccine. The immune system then detects the inactivated pathogen as alien and produces antibodies that can recognise the proteins on its surface. This means the animal’s immune system is prepared to respond again, more quickly, should it encounter the same pathogen in the future.
In a live attenuated viral vaccine, the whole live virus is given to the animal, rather than a dead or inactivated version. With a double-deleted live vaccine, the only difference between the vaccine and an unmodified virus is that some genes are removed to prevent replication. This means a live vaccine can stimulate different parts of the immune system when compared to a dead vaccine.
Because a live vaccine always includes the whole virus, potentially more viral or bacterial antigens are present for the body to produce an immune response to. This means more antibodies are produced in the response, strengthening the potential for the immune system to recognise and respond to the same pathogen in the future, enabling the “one shot” approach. Dead vaccines often require multiple injections to get the same response.
The similarity between the virus and live vaccines can lead to side effects very similar to the disease you are trying to prevent. However, these are usually mild and pass without lasting impact. For example, cattle can get mild respiratory symptoms following the live infectious bovine rhinotracheitis (IBR) vaccine.
The margins in farming are quite narrow these days, which means when a farmer is unwilling to use a vaccine in his or her herd, it usually comes down to time, labour or money.
Live vaccines usually require just one shot, which saves farmers time and labour, as they only need to handle the animals once to administer the vaccine and they will be protected. The author returned from working abroad a few years ago and was surprised to find so many farm clients asking about the new bovine viral diarrhoea vaccine. It costs the same as two injections of the older vaccine, but the convenience of only administering once was very appealing and farmers were prepared to pay for it.
The live IBR marker vaccine has also had an impact in convincing farmers to vaccinate. Being able to vaccinate, and tell the difference between a vaccinated animal and one that has been exposed to the disease, benefits farmers if they need to prove their animals are IBR free – for example, when selling pedigree breeding animals or exporting abroad.
The intranasal IBR live vaccine has also allowed for adoption of vaccines. Uniquely among vaccines, it can help reduce the clinical signs of an outbreak when administered. It is also very fast acting, so the immune response is stimulated within three days, which can help limit the spread when an outbreak has already occurred.
Live vaccines have, therefore, helped uptake of vaccines, as farmers have clearly seen the benefits. The remaining stumbling block tends to be the financial cost – especially when farmers do not perceive that they have a problem with a specific disease. At around £5 an animal for some live vaccines, the initial cost can add up and tight margins lead to the understandable decision to accept the risk associated with not vaccinating.
As vets, we know that when naive herds are exposed to a virus, the infection rate can be especially high, as they have no immunity. But the reality is, often farms begin vaccinating after they have had a problem.
The development of live vaccines is not the only driver encouraging farmers to adopt a preventive approach to livestock health. Having a herd health plan that is signed off by a vet is a requirement for Red Tractor-assured livestock farms and is also part of several supermarket milk contracts. This has led to vets working closely with farm clients to review antibiotics use and put together a plan to prevent the occurrence of the disease, using a combination of management practices and vaccination where appropriate.
Furthermore, the introduction of vet tech services at many practices can support with vaccines uptake by handling the practical aspects of administration. At Willows, the vet tech team supports farmers by ensuring vaccines are given to the right animals at the right time and have been stored correctly to ensure maximum efficacy.
Finally, the COVID pandemic has undoubtedly played a role in highlighting that vaccines have a place in disease control. Seeing the news stories regarding the development and then roll-out of the COVID-19 vaccines over the past 18 months, and what this means for the human world, has made talking about vaccines for livestock more relatable and widely understood.
