Antimicrobials

The terms “antimicrobial” and “antibiotic” are often used interchangeably, but there is a difference. Antibiotics are a class of pharmaceuticals which are substances produced by microbes. Antimicrobials are essentially the same as antibiotics but also include substances of synthetic origin.

Antimicrobials have been used in veterinary medicine since the early 1950’s to prevent and treat disease and improve feed efficiency. These products have an important role in reducing diseases caused by bacteria.

Antimicrobials are used in one of three ways:

1. To treat disease.  This can range from an outbreak of diarrhea in a new group of young calves to treating an abscess on a cat’s tooth.  
2. To prevent disease. While some disagree with this application of antimicrobials, we believe that their “prudent use” is a necessary tool to ensure animal health and welfare.  It isn’t physically possible to feed Canadians without intensive agriculture.  One aspect of intensive agriculture is where many animals are raised together in groups.  Some of these farms can hold thousands of animals.  A simple reality when dealing with large groups of animals (or people) is that a certain proportion will have some form of illness whether it is obvious or not.  Because it is virtually impossible to treat individual animals in these conditions, antimicrobials are administered to the entire group.  Typically, this is for a short duration, and is administered during times of high stress on the animal, such as when piglets are weaned.
3. For growth promotion. The way that animals convert feed into muscle (and then meat) is incredibly complex.  Decades ago, animal health companies discovered that feeding low levels of certain antimicrobials to some species can result in benefits beyond disease treatment and prevention.  Known as the growth promoters, some antimicrobials when administered in feed and water enhance the animals’ ability to convert feed into muscle.  This use of antimicrobials for growth promotion is not without controversy.  However, there are numerous cases documented where farmers have ceased using these products and animal health and welfare have suffered.

Whether used to treat disease, to prevent disease or for growth promotion, each of these products must meet Health Canada’s strict requirements for human and animal safety.

While this is an industry term, it is a very important concept to understand when we talk about antimicrobial use.  To use antimicrobials “prudently” is to:

• Take steps to minimize the need to use antimicrobials;
• When it is necessary to use antimicrobials, to use them properly, such as for the full length of the prescription, at the prescribed dose;
• Only use those antimicrobials when necessary (for example not as a way to minimize the effects of a dirty or unhealthy environment).

Veterinarians play a crucial role in ensuring antimicrobials are prescribed and used prudently.  The Canadian Veterinary Medical Association has developed “Antimicrobial Prudent Use Guidelines for Beef Cattle, Dairy Cattle, Swine and Poultry”.  These guidelines are an excellent tool to help veterinarians manage the use of antimicrobials and reduce the possibility of antimicrobial resistance.

Some bacteria have the ability to survive exposure to an antimicrobial.  When these bacteria survive and continue to replicate and the infection does not go away, antimicrobial resistance can be a cause.  This may require administration of a different, more powerful antimicrobial to target these resistant bacteria. 

Antimicrobial resistance can occur in 3 ways:

1. In any group of bacteria, there are some individual bacteria that are naturally stronger than others.  These stronger bacteria can survive antimicrobial treatment and reproduce more of their kind.
2. A small percentage of bacteria may simply be naturally resistant to certain antimicrobials.
3. Antimicrobial resistance can be transferred from one type of bacteria to another through genetic material called plasmids.

A primary reason to use antimicrobials in food animal production is to help manage disease. By having healthy animals, we have a healthy food supply which leads to healthy people. Access to health management tools such as antimicrobials is important to the practice of veterinary medicine and to farmers so that they can keep the animals in their care healthy.  Veterinarians, just like your own doctor, want to be able to use antimicrobials to ensure animals stay healthy.  Farmers have a similar interest in seeing their herds and flocks stay healthy .  Modern food animal production practices, which include the use of antimicrobials to manage animal disease, are needed as we look to feeding a growing global population on the limited farmland available.  Use of antimicrobials, helps to keep animals healthy while also helping to ensure efficient food production.  Efficient food production will be key to the future availability and affordability of our food supply.  Organic food production practices do not allow the use of antimicrobials to manage disease and animal well-being in herds and flocks.  Consequently, organic production requires more land to produce the same amount of food.  Numerous studies indicate that organic food is no safer than that produced using health management tools such as antimicrobials.

Yes and no.  There are some natural animal health products available that do appear to show antimicrobial tendencies.  They don’t however typically tend to treat or prevent disease for large groups of animals.  Researchers are continuously seeking alternatives to antimicrobials, and are having some luck with new technologies.  Some of this involves genetically modifying organisms to resist disease.  While some consider this a brave new world, these types of new technologies will need to be embraced if we wish to find alternatives to our current practices.