Abstract
The use of antibiotics in agriculture began very soon after the first wide-spread use of antibiotics in humans. During World War II, antibiotics – primarily penicillin – were desperately needed for injured soldiers, so a method of large-scale production was devised (Gustafson & Bowen, 1997). The first published use of penicillin in animals was in 1946, when the drug was used to cure mastitis in dairy cattle. During the 1950s the development of drug resistance was accelerated, and scientists began to be concerned about antibiotic use in animals as well as in humans. There are many pros to antibiotics in agriculture. When antibiotics are routinely given to an entire herd or flock, they will treat any undiagnosed or subclinical infections, especially if the drugs are given at therapeutic levels. Cattle are vulnerable to infections when they are physically stressed, such as when they are shipped, so farmers often give doses of antibiotics to prevent “shipping fever” (Gustafson & Bowen, 1997). One of the cons of using antibiotics is the fact that resistant bacteria can get into the soil via manure and share their resistant genes with other bacteria (Mathew et al., 2007). Plasmids, transposons, and integrons can be passed from one to another, creating huge numbers of resistant bacteria. The influence of integrons is especially powerful and lends itself to producing multi-drug resistant bacteria. The pros and cons of antibiotics in agriculture are both strong, and it is difficult to know what the solution is. Although some countries have banned the use of certain antibiotics in animals such as avoparcin (Denmark & Germany) due to increased VRE, it is unlikely that banning antibiotics will be beneficial at this point. A more moderate approach would probably be better. For example, antibiotics should not be used from growth enhancement because they are given at sub-therapeutic doses.
Use your promo and get a custom paper on
"Antibiotics in Agriculture".
Introduction
The use of antibiotics in agriculture began very soon after the first wide-spread use of antibiotics in humans. During World War II, antibiotics – primarily penicillin – were desperately needed for injured soldiers, so a method of large-scale production was devised (Gustafson & Bowen, 1997). The first published use of penicillin in animals was in 1946, when the drug was used to cure mastitis in dairy cattle. Soon after, chicks given streptomycin were found to grow more quickly, and a byproduct of chlortetracycline manufacture produced faster growth with less feed. By 1950, these drugs were being given to swine and cattle as well (Gustafson & Bowen, 1997). Many livestock farmers were converting to confined rearing, in which animals were kept in small cages while they grew to market weight. In that setting, disease would spread quickly. The four main purposes for antibiotics in agriculture were treatment of sick animals, metaphylaxis to treat and prevent the spread of diseases, prophylaxis given in vulnerable situations such as shipping, and growth promotion (Mathew, Cissell, & Liamthong, 2007). Antibiotic resistance in animals was first noted in 1951, and the drug was streptomycin.
During the 1950s the development of drug resistance was accelerated, and scientists began to be concerned about antibiotic use in animals as well as in humans. In the 1960s, two committees – the Netherthorpe Committee (1962) and the Swann Committee (1969) – came to two different conclusions about use of antibiotics in livestock. The former said there was no risk, while the latter urged regulation and reduction of agricultural antibiotics, in particular, when the drugs were given for growth enhancement. The controversy continued, and over the years the question was asked again by the American Society of Microbiology (1995, 2002), the World Health Organization (1997), and the Centers for Disease Control and Prevention (2013). The WHO (1997) emphasized the danger of antibiotics for growth enhancement, the ASM (2002) counseled surveillance, production of new drugs, and education, while the CDC (2013) reported that bacteria are becoming resistant faster than new drugs are being developed. The effects of drugs taken by humans must be part of any research into antibiotic resistance (Kummerer, 2009).
Pros
As indicated above, there are many pros of giving antibiotics to livestock. For instance, Gustafson and colleagues determined that ionophore antibiotics change the food energy use patterns of ruminants such as cattle by shifting acetates and butyrates to propionate. Thus, the cattle can grow faster with less feed. When antibiotics are routinely given to an entire herd or flock, they will treat any undiagnosed or subclinical infections, especially if the drugs are given at therapeutic levels. Cattle are vulnerable to infections when they are physically stressed, such as when they are shipped, so farmers often give doses of antibiotics to prevent “shipping fever” (Gustafson & Bowen, 1997). Poultry are prone to the fungal infection coccidiosis, so antifungals are an essential preventive measure. All of these increase the economic value of the livestock.
Cons
One of the cons of using antibiotics is the fact that resistant bacteria can get into the soil via manure and share their resistant genes with other bacteria (Mathew et al., 2007). Plasmids, transposons, and integrons can be passed from one to another, creating huge numbers of resistant bacteria. The influence of integrons is especially powerful and lends itself to producing multi-drug resistant bacteria. Bacteria such as Salmonella, Campylobacter, Listeria, Yersinia, and E. coli are common in livestock and can pass easily to humans where they can colonize or infect them. Another bacterium that is quickly increasing is resistant Enterococcus such as VRE – vancomycin resistant Enterococcus (Finley et al., 2013).
Livestock farmers often treat the entire group when a few are sick – an important form of prophylaxis since disease can spread quickly. However, if the dosages are not large enough to kill off all the bacteria, the ones that are left over may become resistant. Landers and colleagues conducted a systematic review of research and found that a substantial number of studies supported their contention that antibiotics given to livestock can increase antibiotic resistance. These included both observational studies and randomized trials. Resistant bacteria were found in the environment of farms, on meat products in store, and causing clinical and subclinical infections in humans. Both direct and indirect effects were found. For example, exposure to farm animals treated with antibiotics can directly produce increased risk of colonization or infection in humans. Transport of animals can cause resistant bacteria to be deposited on the way – an indirect effect (Landers et al., 2012).
Solution
The pros and cons of antibiotics in agriculture are both strong, and it is difficult to know what the solution is (Wichmann et al., 2014). Although some countries have banned the use of certain antibiotics in animals such as avoparcin (Denmark & Germany) due to increased VRE, it is unlikely that banning antibiotics will be beneficial at this point for two reasons. First, the number of resistant bacteria and resistant genes that are presently in the environment is large, so large, in fact, that swine who had been off antibiotics for 14 years and who were carrying no resistant bacteria were colonized by resistant species almost immediately upon exposure (Barton, 2014). Second, livestock are not the only source of resistant bacteria. Humans have been carrying resistance just as long as animals have – penicillin-resistant bacteria were found in humans before 1950. A more moderate approach would probably be better. For example, antibiotics should not be used from growth enhancement because they are given at sub-therapeutic doses, which encourage the development of resistance. Whether or not this is feasible is another question. Research should look into new drugs to be used only for treating sick animals (and people), and non-drug treatments should be investigated.
Conclusion
The use of antibiotics in agriculture is not completely negative, because animals who are sick require treatment, and preventing the spread of a disease is imperative. However, decreasing the routine use of these drugs might be helpful in preserving their usefulness in fighting human and animal diseases in the long term.
- ASM (American Society for Microbiology). (1995). Report of the ASM Task Force on Antibiotic Resistance. Washington, DC: ASM Press.
- Barton, M. D. (2014). Impact of antibiotic use in the swine industry. Current opinion in microbiology, 19, 9-15.
- Centers for Disease Control and Prevention. (2013). Antibiotics Resistance Threats in the United States. Retrieved from http://www.cdc.gov/drugresistance/threat-report-2013/index.html
- Finley, R. L., Collignon, P., Larsson, D. J., McEwen, S. A., Li, X. Z., Gaze, W. H., … & Topp, E. (2013). The scourge of antibiotic resistance: the important role of the environment. Clinical Infectious Diseases, cit355.
- Gustafson, R. H., & Bowen, R. E. (1997). Antibiotic use in animal agriculture. Journal of Applied Microbiology, 83(5), 531-541.
