What is antimicrobial resistance?

Antimicrobial resistance (AMR) occurs when microorganisms (e.g. bacteria, viruses and fungi) develop the ability to survive antimicrobial treatments (e.g. antibiotics, disinfectants) which were previously effective.


What drives the development of resistance?

The use of antibiotics increases the risk of AMR. When antibiotics are used, susceptible bacteria are killed off, but resistant bacteria remain and multiply to create a much larger more resistant population. These resistant bacteria can also spread their resistance genes (resistance ‘blueprints’) to other unrelated bacteria in their environment, meaning antibiotic resistance can jump from one bacterial species to another. This can occur within an animal being treated and in the animal’s environment, such as the soil or slurry pit.


Why is AMR important?

As discussed in our article Dry cow – why change, the World Health Organization recently issued a statement identifying antibiotic resistance as one of the greatest global health challenges faced by human and veterinary medicine. Development of widespread bacterial resistance to our commonly used antibiotics may mean in the future medical treatments such as chemotherapy and surgeries such as hip and knee replacements and caesarean sections may become considerably riskier. While discovery of new antibiotics would help reduce the implications of AMR, research and development of new drugs is slow and bacteria are quick at becoming resistant.


What can we do to slow AMR developing?

There are many ways we can slow the spread of antibiotic resistance. These include:

Preventing the overuse of antibiotics – we can select only the animals which need treating with antibiotics. For example, we can avoid using dry cow antibiotics in uninfected cows, stop the use of blanket oral antibiotics to prevent calf scours and only use antibiotics to treat lame cows where it is appropriate.

Use antibiotics correctly – only use antibiotics registered for the condition you are trying to treat, follow expiry dates, store containers correctly, use the labelled dose rate unless instructed by a veterinarian and always complete the course (which is usually an absolute minimum of three days).

Employ optimal management practices to minimise animal health problems. For example, practice good colostrum management for calves and maintain housing hygiene to prevent calf diseases, use a teat sealant to prevent dry period and spring mastitis.

Vaccinate stock to prevent disease – the role of vaccination primes an animal’s immune system to fight off infection before it can become established. By preventing disease occurring all together, we can completely bypass the need for antibiotics.

Examples of vaccines which are highly effective at reducing or eliminating the need for antibiotic use include BVD vaccines, Rotavec® Corona, Scourguard® 4(K), Salvexin®+B and pinkeye vaccines.

BVD suppresses the immune system of the animal it infects, leading to increased incidence in diseases such as pneumonia and diarrhoea (from bacteria such as Yersinia and Salmonella, parasites and coccidiosis). A well-managed and implemented vaccination programme is likely to reduce viral transmission.

Rotavec® Corona and Scourguard® 4(K) vaccines greatly reduce the incidence of calf scours, lowering mortality rates, preventing checks in liveweight gains and reducing the need for antibiotic use.

Salvexin®+B is highly effective at preventing devastating outbreaks of salmonella in sheep and cattle and the need for large volumes of antibiotics.

Piliguard® administered before the onset of pinkeye season is excellent at removing the need for injectable and topical antibiotics.

We covered this last month, but it doesn’t hurt to mention the traffic light system for antibiotics again here. Antibiotics in New Zealand have been put into three classifications – green, amber and red. These correspond to the importance of the antibiotics for use in human medicine with green being least important and red being critical. As a rule, green should always be used first and red reserved as ‘last resort’ treatments.

RVM consult time is just around the corner and an excellent opportunity to discuss with us how to reduce the risk of AMR on your farm and how we can work together to optimise your animal health.


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