Impact of Antibiotic use in Concentrated Animal Feeding Operations on Human Health

Jessica Michalek, Pre-Veterinary Sciences

John McCluskey, Plant and Soil Sciences

Kelsey Beauregard, Natural Resource Conservation

Salmonella is a disease that is becoming increasingly more common and dangerous. A young boy named Noah Craten was just 18 months old when he was infected with salmonella. This particular strain of salmonella was antibiotic resistant and very difficult to treat. He had to be hospitalized and undergo brain surgery due to a large mass of blood forming in his brain that nearly killed him. He had a line placed directly in his heart and received antibiotics for seven weeks in order to save his life. As a result  the left side of his face now sags and he has a permanent scar on the top of his skull. He also has cerebral spinal fluid in his brain that must be monitored frequently by a physician. This boy suffered greatly and he is not the only one. This particular salmonella outbreak led to double the normal hospitalization rates due to the antibiotic resistance (Terry, L., 2015).

The effects of foodborne diseases are already serious. In the United States alone, salmonella species infections are responsible for about 1.4 million illnesses, 15,000 hospitalizations and 400 deaths annually (Voetsch et al., 2004). Increased prevalence of a multidrug resistant type of salmonella has been found, this poses a major health concern to humans as it is making it harder to treat (Aarestrup et al., 2007). This type of salmonella is an uncommon cause of salmonella in humans worldwide, however in recent years this type now ranks among the most frequently identified salmonella type in several countries. It was the fifth most common type isolated from retail meat in the United States (Aarestrup et al., 2007). This shows that the acquired drug resistance of salmonella enabled it to survive in new environments. There was a reported increase in the proportion of human infections from this type of salmonella  in Thailand, from 0% in 1992 to 2.4% in 2001 (Aarestrup et al., 2007, p. 726). This is significant as it shows an increase in both prevalence and potency of a bacteria due to drug resistances, and it is a prime example of how antibiotic resistance enabled a once irrelevant type of bacteria to become strong enough to pose a threat to human health.

Noah Craten was infected with salmonella from a package of Foster Farms chicken raised on concentrated animal feeding operation (CAFO). When we think of farms we tend to imagine a lot of land and animals grazing. This is not the case for CAFOs. CAFOs are operations where large groups of animals are fed specific diets and not grazing on the land. These operations must have thousands of animals to be considered concentrated. A poultry CAFO would have over 82,000 animals on site and a swine operation would have over 2500 animals (“Natural Resources Conservation Service”, n.d.). These operations have incredibly large numbers of animals going through them and all these animals are fed a specific diet chosen by the producer. The main goal of these operations is to produce large animals to sell for slaughter.

Since CAFOs have such a high volume of animals the animals are more likely to get sick. In order to avoid this, producers put subtherapeutic levels of antibiotics in the animals feed. Feeding subtherapeutic levels of antibiotics means that the producers are not using them to treat an illness, but to promote growth and production in the animals (Gunther, 2013). When you treat an animal with low levels of antibiotics it wipes out all the weak bacteria but the levels are not high enough to destroy the stronger bacteria. This leads to us selecting for only the strongest bacteria that are naturally resistant and will pass their genes on (Nowakowski, 2015). This is a problem that can affect everyone in some way regardless of whether or not you eat meat.

CAFOs have been found to create antibiotic resistance. One study tested over thirty different CAFOs for nine different antibiotic resistant genes and resistance was found at all locations (Brooks, Adeli, and McLaughlin, 2014). Another study sampled retail ground meat and found 84% to be resistant to at least one antibiotic and 53% to be resistant to at least three (White et al., 2001, p. 1148).  A third study found bacteria that is not only resistant to the average antibiotic, but is also cross resistant to an antibiotic used as a last resort to treat multidrug-resistant infections (Chapin, Rule, Gibson, Buckley, and Schwab, 2005).  They also tested for resistance of different antibiotics, some that are used in the swine industry and one that is not (Chapin et al., 2005).  Their results show that CAFOs do indeed create antibiotic resistance because the antibiotics used in CAFOs had resistance whereas the antibiotic that was not used had no resistance (Chapin et al., 2005, p. 139). One final example of antibiotic feed leading to resistance is the use of a class of antibiotics, in poultry, which led to the development of resistant strains (Cronin, 2013). Previously, this class of antibiotics were not used by CAFOs and there was not resistance found;  however, once CAFOs began using them, they found resistance (Cronin, 2013). There is a consensus among scientists that CAFOs create antibiotic resistance.

CAFOs are not only creating antibiotic resistant bacteria but they inevitably spread it to the human population. Transfer occurs in multiple different ways including through meat and the environment. Samples of ground meat tested positive for different strains of salmonella and  antibiotic resistance.  Five different strains of salmonella were identified in the meats that are resistant to nine different types of antibiotics (White et al., 2001). If someone eats this meat and the salmonella is not killed they would get very sick with an antibiotic resistant bacteria. This bacteria is difficult to treat and may not respond to a simple round of antibiotic treatment. These meats all came from different CAFOs and had been processed at different slaughterhouses showing that this is a widespread problem (White et al., 2001). It is not just one or two operations causing the problem it is the whole system of feeding antibiotic feed. Research was done to test the quality of air inside a swine CAFO. They found that there were very high levels of antibiotic resistant bacteria inside the operations themselves (Chapin et al., 2005). Research further proved this by comparing levels of antibiotic resistant bacteria inside the CAFO to areas upwind from the facility; they found concentrations of multidrug resistant bacteria to be 2.1 times higher inside the facility (Gibbs et al., 2006, p. 1034). This means that people who work in the facility are exposed to these high levels of resistance everyday and could easily transmit an antibiotic resistant strain to people outside the facility. Inhalation of these bacteria could lead to the sick person having almost no treatment options (Chapin et al., 2005). These multidrug resistant bacteria are not just found inside the operations, they are also found in the air around the facility and affect the nearby communities. It was found that the same high concentrations of multidrug resistant bacteria can be found 150 meters downwind of the facility (Gibbs et al., 2006). The antibiotic resistance can truly affect anyone. Not eating meat does not protect you from exposure to antibiotic resistant bacteria.

The United States needs to enforce bans on antibiotic feed used in livestock operations, especially restricting the use of antibiotics that are vital to human medicine. It is important to monitor our levels of antibiotics and what we are using them for. The United states currently does not keep records on antibiotic usage so farmers are not being held responsible for what they use. In order to get a handle on our antibiotic use we need to ban the subtherapeutic use of antibiotics and even regulate what antibiotics are given to livestock to treat diseases. It would be best to use ones that are not common in human medicine. Most importantly the United States needs to track its usage in order to make a difference.

In Europe antibiotic resistance has already been noticed and steps have been taken towards fixing it. Denmark in particular has made huge strides in reducing their antibiotic resistance and the United States should follow their lead. The use of antibiotic feed in CAFOs leads to more antibiotic resistant bacteria being spread and adopting the same standards as Denmark will help protect human lives in the United States. Denmark is the world’s leading exporter of pork and they banned all subtherapeutic uses of antibiotics in swine by 1999. Since these bans they have found significant decreases in levels of antibiotic resistant bacteria (Levy, 2014). “From 1992 to 2008, antibiotic use per kilogram of pig raised in Denmark dropped by more than 50%. Yet overall productivity increased. Production of weaning pigs increased from 18.4 million in 1992 to 27.1 million in 2008” (Levy, 2014, para. 15). They did not just ban the use of antibiotics for growth promotion, but also limited their use for disease prevention (Charles, 2012). While cost of raising these animals has gone up by about $1.14 the animals have lower disease rates and more efficient production (Levy, 2014, para. 16).  Human health should be prioritized over economic gain. Denmark closely regulates the amounts of antibiotics used and the types given to the animals.

Despite all of the scientific consensus on antibiotic resistance and how it poses a serious problem for humans humans, there are still some concerns that should be addressed.  One major concern is if the use of antibiotics is stopped then the cost of meat will increase. In 1999 it was estimated that it would have cost CAFOs $45.5 million if the drug use was banned (PBS, 2014, para. 18). However, this is including their profit, not all of that would be passed on to consumers. Also, feed that does not contain antibiotics costs 1 penny less per chicken, with the cost also being less in other animals (Parsons, 2007). Unfortunately, the American people may need to accept that they will have to pay a bit more for their meat in order to properly take care of their health like Denmark has. Denmark also managed to increase their production using their new system and the same could happen in the United States (Levy, 2014). If no change occurs, drug resistance will become more of a problem then it already is and we will be unable to find cures for our sickness, which would result in families spending hundreds if not thousands of dollars trying to find an answer to the sickness.

 A second concern of sceptics is the ever growing demand for more food. Ultimately, the use of antibiotics in feed only leads to about a 3 percent increase in size of the animals, which is really not substantial (PBS, 2014). As stated previously, Denmark is still the lead exporter of pork despite banning all subtherapeutic antibiotic use. CAFOs first came into existence in the 1970’s by chicken producers and were created so they could have a large number of animals and decrease production costs (History of CAFOs, 2011). However, we do not need them in order to produce enough animals to feed our population. Denmark evolved their way of farming so that they could still produce large amounts of pork for the population. So, despite popular belief antibiotic feed is not the answer to how we will feed the growing population.

Another concern to address is people wondering how we will treat sick animals without the use of antibiotic feed. This is actually quite simple to address. The main concern of antibiotic resistance comes from antibiotic feed, not injections, which is what is used to treat sick animals. Antibiotic feed is used as a growth hormone and preventative measure, not to treat sickness. As long as the antibiotics are used to treat disease and this is monitored by a veterinarian to make sure the antibiotics are not misused they can still be used to treat diseases in animals.

One final concern could be whether or not the way Denmark is handling eliminating antibiotic feed and resistance is transferable to the United States. The answer to that concern is yes, the American people just need to focus their priorities on protecting their health and their family’s health. Denmark simply changed the way they look at farming. In order to be successful without antibiotic feed they had to move away from the CAFO style of production. When animals are all kept close together there is a higher risk of disease spread, therefore they have moved into a more spacious style of farming (Kennedy, 2011). The United States could easily do this as we have significantly more land than Denmark that we could put towards farming. Instead of containing lots of animals in small spaces we could allow them to have space and significantly decrease the need for antibiotics in the first place.

Antibiotic resistant bacteria are a major health threat because they make it harder to treat illnesses caused by these bacteria. CAFOs are closed off, high volume operations and the animals in them are more likely to get sick. The sub-therapeutic levels of antibiotics which are put into these animals feed has led to an increase in antibiotic resistant bacteria, this is why the US needs to adopt the same standards as Denmark and ban all sub-therapeutic use of antibiotics in livestock operations. Doing so will decrease antibiotic resistant bacteria levels and make livestock products safer for humans.




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