October 9, 2001 Presentation to the Leggatt Inquiry Jointly presented by Dr. Warren Bell of the Canadian Association of Physicians for the Environment (CAPE) and Sergio Paone, Ph.D., Anima Mundi Environmental Consulting. Human Health Risks Associated With Salmon Farming Most of the salmon produced in BC now comes from open netcage farming rather than traditional fisheries. In fact, it seems clear that the general policy direction of the Department of Fisheries and Oceans favours the development of salmon farming. This shift introduces direct human health risks and other negative impacts, some of which are similar to those associated with the farming of land-based animals. The consumer's opportunity to select meats that are free of these risks is being reduced. For farmed salmon these risks include: Drug residues in farmed salmon and in other seafood, like shellfish, that are wild but live in the vicinity of the salmon farm. Increases in antibiotic resistance among bacteria carried by farmed fish, which can in turn pass on resistance to bacteria that cause human disease. Exposure of salmon farm workers to antibiotics and other chemicals used on the farm. Changes in the nutritional value of farmed salmon relative to wild salmon. Net loss of protein for human consumption as a result of feeding wild fish to farmed salmon. These risks may be divided into two categories. Some risks, like chemical residues in and the nutritional value of farmed salmon, are of concern mainly to the individual who consumes it. Other risks, however, have broader global and social implications, and should also be of concern to those who choose not to eat farmed salmon. In this second category fall the risks such as the development of antibiotic resistance and the risk of depletion of global seafood supplies. Drug residues Antibiotics, and other drugs, are administered to farmed salmon only when a disease outbreak is identified. In contrast, other animal farming industries also administer antibiotics on a prophylactic basis (to prevent disease from occurring) and as growth promoting agents (subtherapeutic levels of antibiotics, which increase animal rate of growth). The drugs are usually administered as additives in the feed. In an effort to prevent drug residues in salmon heading for market, a withdrawal time is mandated. This is to allow time for salmon to excrete the drug from their bodies. The BC provincial Aquaculture Regulations state that salmon are not to be harvested less than 105 days after being treated with drugs, unless federal Food and Drug Regulations specifies a different standard or a veterinarian has prescribed a different minimum withdrawal period (1). The potential human health effects that are associated with drug residues are toxicity allergic reactions and the development of antibiotic resistance in bacteria affecting humans. Prior to 1997, it was the responsibility of the federal Department of Fisheries and Oceans (DFO) to inspect farmed salmon for the presence of drug residues. This ended in 1997, when the Canadian Food Inspection Agency CFIA) was created under Health Canada to, among other duties, inspect all meats for drug residues. In both BC and eastern Canada, the two main classes of antibiotic residues monitored are sulfonamides and tetracyclines. In addition, as small number of farmed salmon in BC are tested for ivermectin, a parasiticide used to combat sea lice. The CFIA compares the results of the drug residue tests with the Minimum Recommended Level (MRL), a concentration established by regulation. A particular batch of farmed salmon is considered to be a health hazard if the sample shows drug residues above the MRL. Three main issues with respect to the CFIA farmed salmon inspection program are: The amount of harvested farmed salmon produced with drug residue levels above the MRL. The reliability and thoroughness of the CFIA farmed salmon-testing program. Actions is taken by CFIA when high drug residue samples were found. We will now look at these three points in more detail. How much harvested farmed salmon contains high drug residues? Results of all tests for drug residues in farmed salmon were obtained from the Federal government through a Freedom of Information Act search. Between 1997 and 1999, 0.4 to 1.1 % of the farmed salmon tested in British Columbia showed drug residues above the MRL. For New Brunswick, data was only available to us up to 1998. The fraction of samples in that province that were above the MRL was 5.5% in 1997 and 1.5% in 1998. In Newfoundland, drug residue tests were only conducted between 1990 and 1994 (with the exception of 1 fish each in 1997 and 1998, which is not statistically significant). From 1990 to 1994, an astonishing 29 to 50% of farmed salmon tested showed drug residue levels above the MRL. Although the percentage of farmed salmon contaminated with drug residue for BC and New Brunswick is small, the amounts are significant when one looks at the weight of farmed salmon that they represent. Table 1 summarizes this. Table 1:Summary of farmed salmon production & amount produced with antibiotic residue levels above the MRL for all provinces tested. Province Year British Columbia " " New Brunswick " Newfoundland 1996/97 1997/98 1998/99 1997 1998 1993 Total Farmed salmon production (tonnes) 27,756 36,465 42,200 18,585 14,232 100 Amount produced with antibiotic residue above MRL (tonnes) 108 397 190 1022 213 50 How reliable is the CFIA Farmed Salmon Inspection Program? When looking at the above results for drug residues found in farmed salmon, one must bear in mind that there are several identified problems related to how the CFIA conducts it's inspections. A June 2001 report, by Minister of Public Works and Government Services Canada, assessed the CFIA testing of aquaculture products (2). The report found that drug residue tests were not conducted for all the drugs used on salmon farms. Also, the amount of testing did not always reflect the level of production, or the pattern of drug use. Some important examples of this are as follows: Florfenicol is an antibiotic widely used on fish farms in BC, yet the CFIA has done no analysis for residue. In 1999, 33% of all medicated feed in BC contained florfenicol. A new drug, Emamectin Benzoate (not yet approved for this use, but available by veterinary prescription), has been used in salmon farms in the Maritimes since1998. Its residue is not being tested for even though, in 1999, 38% of all medicated feed in the Maritimes contained this drug. In March, July and October of 1999, no drug residue tests of any kind were conducted in BC. This despite the fact that these three months accounted for 25% of farmed salmon production and 28% of drug use for the year. In the Maritimes, 31% of all residue tests for 1999 were conducted in December, a month that accounted for just 12% of farmed salmon production and a mere 2 % of drug use. Response of the CFIA when high residue levels are found. The stated purpose of the CFIA testing program is to prevent the public from being exposed to the health risks associated with consuming farmed salmon with high drug residues. Despite this formal commitment, the actions of the CFIA do not always clearly reflect such a goal. In the above mentioned assessment report of the CFIA(2), the response of the CFIA was reviewed for eight recent cases where tests showed fish with drug residue levels above the MRL. Most of the efforts of the CFIA went into investigating the root cause of the high levels. However, their efforts in preventing contaminated farmed salmon from reaching the consumer wholly inadequate. Some problematic examples are: In only two of the eight cases of contaminated fish that the report reviewed, did the CFIA initiate a farmed salmon product recall. The time it took to get test results was up to several weeks, by which time the farmed salmon had been sent to market, bought and consumed by the purchaser. The criteria for recall used by the CFIA were not always clear. In one of the eight recent cases, the Agency used a 1994 Health Canada health risk assessment which gave 0.2 parts per million (ppm) as the 'safe' residue level for oxytetracycline this conflicts with the standard of 0.1 ppm which was the MRL at the time of the test. The CFIA also investigates consumer complaints related to illnesses from fish products. Between 1997 and 1999, the CFIA assessment report reviewed 15 complaints that involved farmed fish. They found that; " in almost all cases, documentation was incomplete and that it was not possible to evaluate the appropriateness of the investigations. We noted that in three cases, the reported symptoms were allergic reactions, and there is no evidence to show that the presence of drug residues, which are recognized to be potential allergens, was investigated as a possible cause." As currently conducted, salmon farming results in the production of some farmed salmon with drug residue levels above the minimum recommended by Health Canada. The Canadian Food Inspection Agency, under current programs, does not adequately sample for these drug residues and does not prevent most of the farmed salmon it finds to be hazardous for consumers from reaching market. Drug residues in wild seafood. Neither the CFIA nor the DFO routinely test wild seafood in the vicinity of salmon farms for drug residues. Yet the drugs administered to farmed salmon do make their way into the marine environment. A few studies have shown that these drugs also find their way into nontarget organism as well. Some findings from this research include (3): 88% of 189 fish caught in the vicinity of fish farms had levels of antibiotics above the MRL. The presence of antibiotic residues above the MRL in wild fish caught up to 400 metres from a fish farm. Drug residues present in mussels and oysters collected in the vicinity of fish farms in Norway and Finland. There is no program in Canada that monitors drug residues in wild fish near salmon farms. Such a program would be useful in order to warn the public of times when the harvesting of wild fish or shellfish near salmon farms should not be conducted. It would also clarify how much drug residue is making its way into wild ecosystems, something that at present is completely unknown. Antibiotic Resistance It is well established that repeated use of antibiotics to treat bacterial diseases leads to selection of and increase in the population of antibiotic-resistant strains. As early as 1991 it was estimated that 50% of the bacteria responsible for a salmon disease called furunculosis in Scotland were resistant to oxytetracycline (4). In British Columbia, strains of furunculosis resistant to three approved antibiotics have been described since 1993 (5). In addition to bacteria that cause specific diseases such as furunculosis, many other bacteria in the marine environment in the vicinity of fish farms have been found to be resistant to antibiotics used on the farms (6,7). Does this increase in antibiotic resistance in bacteria associated with farmed fish and their marine environment lead to resistance in bacteria that cause disease in humans? Strong evidence says yes, it does. Consider the following: Several types of bacteria recovered from salmon or their marine environment can lead to disease in humans (8, 9). Resistant strains of bacteria causing animal disease can transfer their antibiotic resistance to human bacteria (10,11) One family of bacteria that are found in many places in nature, including both humans and fish are enteric or gut bacteria. Among this family are various strains of E. Coli, Salmonella and Serratia, which can leads to various diseases in humans, often resulting from is often the consumption of meat that has been improperly processed or stored. Research indicates an increase in antibiotic resistance in these types of bacteria worldwide. In 1999, Alexandra Morton, a Vancouver Island biologist, caught a farmed salmon shortly after an escape from a salmon farm. Samples from the salmon were sent for analysis. The results showed that the salmon was infected with Serratia liquefaciens and Serratia plymuthia, two enteric. Disturbingly, the bacteria showed resistance to 11 of the18 antibiotics tested on them, including several antibiotics used to treat human diseases (9). The Serratia family of bacteria is interesting in that, until recently, they were considered relatively harmless to humans. In recent years it has also become clear that the Serratia bacteria are opportunistic and can cause severe illness, such as respiratory and urinary tract infections, in humans. The Serratia liquefaciens bacterium is responsible for 5 blood transfusion related deaths in recent years in the U.S.A (10). Transfer of antibiotic resistance. In the above examples, antibiotic-resistant bacteria from fish can present a health hazard to humans because these same bacteria also cause human diseases. But what of the other bacteria associated with fish and their marine environment that develop resistance but are not directly pathogenic to humans? These also represent a health risk because antibiotic resistant bacteria have the ability to transfer that resistance to other bacteria that have never been exposed to antibiotics. This is done through the transfer of a plasmid, a piece of genetic material, from the strain of bacteria that has developed resistance to one that hasn't. The problem of an increasing incidence of antibiotic resistant strains of bacteria is a severe one, both in animal husbandry and in the treatment of human diseases. Many bacterial infections in humans are proving difficult to treat with conventional antibiotics because of the appearance of massive resistance. As we saw earlier, diseases that are a problem on fish farms are also becoming more difficult to treat with conventional antibiotics. In the past, these two areas of antibiotic use have been treated as separate. But can an increase in resistance among fish diseases in the marine environment occur without any consequences for human health? A recent study strongly suggests not. This research examined the distribution of oxytetracycline resistant bacteria in aquaculture environments and in hospitals, and concluded that "the aquaculture and human compartments of the environment behave as a single compartment" (12). In this study, oxytetracycline resistant strains of Aeromonas bacteria were isolated from fish farms and from hospital sewage. It was found that the plasmid, which genetically encoded the resistance in the bacteria, was identical in bacteria from both environments. Furthermore, both the fish farm and hospital bacteria were able to transfer that plasmid to strains of E. Coli, bacteria commonly found in the intestines of humans. This study provided direct evidence, for the first time, "that related tetracycline resistance-encoding plasmids have disseminated between different Aeromonas species and E. Coli and between the human and aquaculture environments." This transfer of antibiotic resistance through the free exchange of genetic material has prompted researchers, such as professor Stuart B. Levy, director of the Centre for Adaptation Genetics and Drug Resistance at the Tufts University School of Medicine, to state: “The exchange of genes is so pervasive that the entire bacterial world can be thought of as one huge multicellular organism in which the cells interchange their genes with ease.” Any measure increasing of antibiotic resistance for any bacteria, increases the genetic reservoir of resistance available to all bacteria. Put another way, our capacity to treat human diseases with antibiotics is a non-renewable resource. Every time we use antibiotics, we diminish that capacity a bit more. If we use antibiotics other than for the treatment of human diseases, we must be very careful that such use is urgently justified, and is managed impeccably. At present, it seems clear that the use of these powerful drugs in fish farming is neither. Nutritional Risks Fat Content The feed given to an animal and the conditions under which it is kept will influence the animal’s composition. It is well known that wild land-based animals are leaner than their domestic counterparts. Not surprisingly this is also the case for salmon. As early as the 1980’s, Canadian consumer groups and health agencies expressed concern over the fat content of farmed versus wild salmon. Not only is the fat content of farmed salmon higher than that of wild salmon, but the composition of farmed salmon fat is less healthy than the that of wild salmon fat. Table 2 summarizes this. The fats most strongly associated with human disease are saturated fats. Saturated fats are available in many foods that we eat, primarily those of animal origin. The average North American diet tends to supply much more saturated fats than the body needs. Saturated fats contribute to heart attack, bowel cancer, gallbladder disease, and stroke. Poly-unsaturated, and mono-unsaturated fats are far more healthful, especially the ones known as the essential fatty acids (EFAs). The body cannot produce EFAs and we must get them from our diet. These latter fats are divided up into omega-3 and omega-6 fatty acids. While both are needed, health experts agree that it is important to consume foods that are ample in omega-3 fats, as these confer many of the most desirable health benefits to humans. Excessive consumption of omega-6 fatty acids, on the other hand, can aggravate health problems. While omega-6 fats are widely available from many sources, omega-3 fatty acids are more difficult to obtain; the best source is from various types of seafood. Table 2: Fat Composition comparison among various fish. Data obtained from the United States Department of Agriculture nutrition database (12). Based on 100 gram serving of raw fish. Type of fish Total fat content Omega-3 to omega-6 % of total fat that is (grams) fatty acid ratio omega-3 fatty acids. Farmed Atlantic salmon 10.85 1.1 18% Wild Atlantic salmon Farmed coho Wild coho Wild chinook Wild chum salmon Wild pink salmon Wild sockeye Wild mackerel Wild anchovies 6.34 7.67 5.93 10.44 3.77 3.45 8.56 7.89 4.84 3.9 2.3 3.2 4.1 4.7 5.2 2.3 5.0 9.3 32% 17% 25% 16% 20% 33% 15% 20% 33% Table 1 compares the fatty acid composition for various types of fish. It can be seen that farmed Atlantic salmon has 70% more fat than wild Atlantic salmon, and farmed coho has 30% more fat than wild coho. Of specific interest to BC, however, is the comparison of farmed Atlantic salmon (which accounts for 85% of farmed salmon production in BC) to the five Pacific species of salmon. Farmed Atlantic salmon is about 200% higher in fat than wild pink or chum salmon, 83% higher than wild coho, 27% higher than wild sockeye, and about the same in total fat as wild chinook. It is also interesting to note that farmed Atlantic salmon has significantly more fat than jack mackerel and anchovies, two of the species that are used to make feed for farmed salmon. If we now look at the last two columns in Table 1, which show the percentage of total fat that is composed of omega-3 fatty acids, and the omega-3 to omega-6 ratio, the nutritional difference among the different fish becomes even clearer. The highest percentage (32 to 33%) of omega-3 fats is found among wild pink salmon, anchovies, and wild Atlantic salmon. The group with the second highest percentage range (20 to 25%) is wild coho, chum, and mackerel. The lowest percentage (15 to 18%) of omega-3 fats is found among farmed Atlantic and farmed coho salmon, as well as wild chinook and sockeye. Also, compared to Atlantic salmon, the other fish in table 1, including chinook and sockeye salmon, have much higher omega-3 to omega-6 fat ratios, an important factor for health considerations. For nutritional quality based on total fat, percentage of omega-3 fats, and the omega-3 to omega-6 fat ratio, farmed Atlantic salmon is the least desirable food source of all the above. Net Loss of Seafood. Salmon farming proponents often state that, since wild fisheries are collapsing all over the Planet because of over-fishing, farming the oceans is necessary to feed a hungry world. They claim that the fish farming industry can supply food while taking pressure off wild ocean resources. This position is disingenuous and simplistic. The resource consumption of aquaculture (the farming of a seafood species) varies, depending on what species is farmed and what method is used. With regard to taking pressure off ocean resources, a key factor is whether the species being farmed is carnivorous or not. There are more than 250 different species of seafood currently farmed in the world and about 85% of the total production is made up on non-carnivorous species. In British Columbia, however, the majority of aquaculture production consists of salmon. Salmon are carnivores. In order to try and mimic their natural diet, carnivorous species are given feed that is high in fishmeal and fish oil. These key ingredients are obtained from wild fish such as sardines, mackerel and anchovies, which are mainly supplied by South American wild fisheries. From an ocean resource point of view, the total amount of wild fish used to make feed for farmed salmon, compared to the total amount of salmon produced is of critical interest. But this ratio is not recorded by the fish farm industry. Since feed is one of the most expensive components of a salmon farm operation, fish farmers track the Feed Conversion Ration (FCR), which is how much dry feed is used to make a given amount of salmon for market. The average FCR for BC salmon farms is currently about 1.3 4 (1.3 tonnes of dry feed needed to make 1 tonne of fish for market). But this amount represents only a fraction of the weight of actual fish used to make fish farm feed. The real question is: what weight of wild fish is needed to make that 1.3 tonnes of feed? It is the fish oil component of salmon feed that consumes most of the wild fish used to make that feed. Consequently, in order to obtain enough of this prized component, it is necessary to use about 3 kilograms of wild fish to produce the 1.3 kilograms of fish feed. This in turn is used to produce one kilogram of farmed salmon. Rather than taking pressure off ocean resources, salmon farming is currently adding greatly to that pressure. It takes 3 kilograms of wild fish to produce one kilogram of farmed salmon. As a result, salmon farming results in a dramatic net loss of fisheries resources. How did we get here? And how do we move on? How did we get here? This paper has outlined serious problems vis à vis human health, both local and shortterm, and widespread and long-term, associated with salmon farming as it is now practiced in B.C. Not addressing these problems will result in the steady exacerbation of human health issues on a number of fronts. We believe that there are solutions to all the problems we have outlined. But first, we would like to offer some brief comments on possible reasons why the current situation has developed. There is a fundamental conflict of interest inherent in the role of the CFIA (a conflict of interest shared with other regulatory bodies). On the one hand responsible for monitoring the Canadian food supply to ensure its safety and value, this CFIA is also mandated to promote sales of Canadian food products and enhance the amount and dollar value of food sold. It is impossible to serve two masters well, especially if their goals are in absolute conflict. Let us furnish some examples. There has been a long tradition of denial of the inter-relatedness of ecosystems, to some extent within the scientific community and the citizenry at large, but today increasingly isolated to parts of the commercial and regulatory sectors. Such a view is at odds with current, wellvalidated data, as we have shown above (11,12). But if a regulatory agency such as the CFIA has a vested interest in promoting product sales, then its staff will be encouraged, at the level of policy and operations, to ignore or downplay evidence of adverse ecological and human health impacts of the industry it monitors. Researchers at the University of Illinois have recently shown conclusively, using DNAamplification methods, that antibiotic resistance is created in bacteria in hogs. These bacteria disperse from hog barns throughout streams and other surface waters (14). This is in accord with the findings related to aquatic systems which we have noted above (11,12). If land and sea-based farming operations spread antibiotic resistance, why would the CFIA not take decisive action to address this issue? Why would containment of fish farm residues not be a sine qua non of permitted technologies in B.C and throughout Canada? The only explanation, we believe, is that the agency is unable to take human and ecosystem safety concerns seriously because it is internally biased against these concerns when they conflict with its other mandate, that of promoting and enhancing sales of Canadian food products. Only thus can one explain the gross inadequacies in its monitoring activities, and its acceptance of technologies that contribute to the generation of negative impacts. These include: test results available only after food has been consumed; an exceptionally incomplete pattern of monitoring; inaction by the agency when confronted with stark scientific evidence of burgeoning antibiotic resistance problems and transference of resistance to human pathogens; and most critically, the lack of serious discussion of the net loss of seafood resources resulting from salmon farm feeding practices. How do we move on? Solutions exist for the current dilemmas in salmon farming outlined by this paper. Without being exhaustive, they include: 1) Separating out the regulatory mandate of the CFIA from its mandate to promote food sales and production. Whether this is done by creating a separate agency or some other means, it is time for some agency to work solely for the protection of human and ecosystem health (which are indissolubly linked) vis à vis the food system. 2) Converting the current open cage system to an exclusively closed system. Currently there are pilot projects in progress to determine the viability of several types of closed fish farm systems. These projects need to be expanded and properly supported by both Federal and provincial governments. 3) A hard look at the issue of net loss of seafood resources. We believe a scientific panel should be struck to examine this issue and give guidance to the industry and its regulators. 4) Widespread acknowledgement and promotion of the scientifically verified principle of ecosystem interconnectedness. The source of much of the inadequate regulatory actions and of the alarming passivity of the CFIA and other governmental agencies arises from denial of this fundamental principle of living systems. What we do to fish on fish farms, to hogs in hog barns, to soybeans in farmers’ fields, and to ourselves in human communities, affects all other components of the one unified Planetary ecosystem. To ignore this principle is to create conditions for future generations that will make their lives straitened and impair their well-being in known and unimaginable ways. We do not believe it is our right to permit open-cage salmon farming, or any other activity with disruptive effects on human and ecosystem health, to continue without correction. We hope that this Commission will agree with us that drastic changes are needed, both short and long-term, in the way salmon farming is conducted in this province and this country. We hope that the Commission will not be swayed by rhetoric and unsubstantiated claims, but will focus on scientific evidence and unequivocal documentation. References 1) BC Environmental Assessment Office. 'Salmon Aquaculture Review', 1997, Volume 1, page 41. 2) Minister of Public Works and Government Services Canada. 'Health Canada Food Safety Assessment Program: Assessment Report of the Canadian Food Inspection Agency Activities Related to the Safety of Aquaculture Products'. June 2001. Available on the Health Canada Website at http://www.hc-sc.gc.ca. 3) EVS Environmental Consultants. In 'Impacts of Freshwater and Marine Aquaculture on the Environment: Knowledge and Gaps (Preliminary Report). Prepared for Canadian Department of Fisheries and Oceans, June 2000, pp. 12. 4) Richards, R.H., et. al. Variations in antibiotic resistance patterns of Aeromonas salmonicida isolated from Atlantic salmon (Salmo salar) in Scotland. In: C. Michel and D.J. Alderman (eds.). Chemotherapy in aquaculture: from theory to reality. Symposium Paris, March 12-15, 1991. Office International des Epizooties, Paris, France, pp. 276 - 287. 5) Ellis, D. and Associates. (1996). Net Loss: The Salmon Netcage Industry in British Columbia. A report to the David Suzuki Foundation, pp. 107-108. 6) Lunestad, B.T. Fate and effects of antibacterial agents in aquatic environments. In: Chemotherapy in aquaculture: from theory to reality. Symposium Paris, March 12-15, 1991. Office International des Epizooties, Paris, France, pp. 152 - 161. 7) Smith, P.M., et. al. Bacterial resistance to antimicrobial agents used in fish farming; a critical evaluation of method and meaning. Annual Review of Fish Diseases, Vol. 4: pp. 273 - 313, 1994. 8) Ellis, D. and Associates. (1996). Net Loss: The Salmon Netcage Industry in British Columbia. A report to the David Suzuki Foundation, Appendix 14. 9) Morton, A. (1999). Lab report from Fish Pathology Lab, Ontario Veterinary College, University of Guelph, submitted to Alexandra Morton, on the results of analysis of swab samples taken from an escaped Atlantic salmon in the Broughton Archipelago, BC. 10) Roth, V. Blood product Contaminated with unusual bacteria. Presented at the Interscience Conference on Antimicrobial Agents and Chemotherapy, September 26 - 29, 1999, San Francisco, California. 11) Midtvedt, T., et. al. Putative public health risks of antibiotic resistance development in aquatic bacteria. In: Chemotherapy in aquaculture: from theory to reality. Symposium Paris, March 12-15, 1991. Office International des Epizooties, Paris, France, pp. 302-314. 12) Rhodes, G., et. al. Distribution of oxytetracycline resistance plasmids between Aeromonads in hospital and aquaculture environments: Implication of Tn1721 in dissemination of the tetracycline resistance determinant Tet A. Applied and Environmental Microbiology, Vol. 66(9): pp. 3883 - 3890, Sept. 2000. 13) United States Department of Agriculture Database. Available at http://www.nal.usda.gov/fnic/cgibin/nut_search.pl. 14) ‘Conclusive link between hog mega-barns and antibiotic-resistant bacteria.” Union Farmer Monthly Vo52:5, pg.7, August, 2001.