Tara Donovan, DVM
I hope you were able to attend the 2012 AASV Annual Meeting and are finding ways to implement some of the new ideas presented. One topic from the meeting that I keep pondering about is how we measure success or failure of antibiotic use on the farm. Concerns over antibiotic resistance and the nontherapeutic use of antibiotics have been all over our trade publications the past few weeks. In January, the Food and Drug Administration (FDA) announced they are banning several extra-label uses of cephalosporins in food animals in order to protect that important class of antimicrobial drugs used to treat human illness.1 This goes into effect on April 6. A more recent announcement: the FDA has been issued an order by a federal judge to ban the uses of growth-promotant antibiotics in food animals.2
At the AASV meeting, Dr Dan Thomson challenged us to identify outcome variables that we can accurately monitor to determine animal health program success or failure.3 When it comes to antibiotic treatment in the barn, we can monitor the general health of the group by close-out mortality, average daily gain, and cull rate of the group. We typically don’t measure treatment success of the group or, at an even more detailed level, treatment success in the individual pig. However, individual treatments are recorded, but the outcome of that treatment is typically not tracked or calculated. In Dr Thomson’s presentation, he told us that in one case, 24% of the cattle in a group were treated for respiratory disease. Upon evaluation of the lungs of this group at processing, 62% of the cattle had lung lesions. In this case, 43% of the animals that had lung lesions were not identified and treated when they were ill. Even worse, one third of the lesions noted at the plant were so severe the viscera were adhered to the rib cage. This is when the health issue in the group quickly becomes a food safety concern. Dr Scott Hurd recently discussed a study that showed for every 1% increase in peelouts (adhesion of the viscera to the carcass: pericarditis, pleuritis, peritonitis), there was a 5% increase in contamination of the carcass with Enterococcus and Campylobacter at processing.4 In addition, his recent study showed that carcasses having visceral lesions were 90% more likely to have Salmonella contamination than carcasses without lesions. One additional note from his study was that carcasses from swine raised without use of antimicrobials were significantly more likely to be contaminated with Salmonella than those raised conventionally where antimicrobials were used. We can’t ignore that as we advise on the care and welfare of live pigs; we are producing food and the risk unhealthy animals have on carcass contamination is concerning. This possible association between carcass lesions and foodborne pathogen contamination needs to be further studied.
As I pondered some more, another study came to mind, where the rate of pathogen infection in swine raised in antibiotic-free farms was compared with that in a conventional pork production setting.5 Three farms in each category were studied. The pigs raised outdoors without antibiotics had higher rates of three foodborne pathogens than did pigs on conventional farms which remained indoors and received preventive doses of antimicrobial drugs. In addition, an alarming finding was the presence of two parasites, Toxoplasma gondii and Trichinella spiralis, in the antibiotic-free tested farms.
The benefits of antibiotics in food animals are vast and should not be taken for granted. Their part in keeping herds healthy and food safe will continue to be studied in order to better understand the impact on human health in regard to food safety. The use of antibiotics for prevention of disease is a use that we must continue to defend and prove using the measurement of treatment outcomes.
What is your part? Your part is having antimicrobial stewardship in your antibiotic recommendations. We need to continue to understand the treatment outcomes of the therapies we recommend by using variables that can be accurately measured to provide us with data to make decisions. Improving data collection on the farm must include morbidity and outcomes such as percent of treated animals that resulted in the pig being sold to the primary market, percent of animals re-treated, and mortality of treated versus untreated animals. Understanding not only the outcome but also the number of days to cure or days to retreat will increase our ability to fine-tune our therapy and make better decisions on antibiotic use in farms. Teaching and encouraging producers to devote time to accurate record-keeping of treatments to allow follow-up on the outcomes will further guide us and support the decisions we make. In addition to measuring therapeutic outcomes, we need to continue to promote early identification of sick pigs and training care givers on how to identify the pigs and administer therapy.
I will take the challenge to better understand success and failure of antibiotics I recommend. The success of our medical treatments impacts the pigs’ health, but also food safety and potentially human health. Let’s be stewards of the profession and safeguard antibiotics by ensuring their judicious use.
References
1. Food and Drug Administration. FDA to protect important class of antimicrobial drugs for treating human illness. 2012. Available at: http://www.fda.gov/NewsEvents/Newsroom/PressAnnouncements/ucm285704.htm. Accessed 30 March 2012.
2. Ruling affects feed-grade antimicrobials. March 28, 2012. https://www.aasv.org/news/story.php?id=5507. Accessed 30 March 2012.
3. Thomson DU. Applied population medicine in food animal systems. Proc AASV. 2012;417–422.
4. Hurd HS, Yaeger MJ, Brudvig JM, Taylor DD, Wang B. Lesion severity at processing as a predictor of Salmonella contamination of swine carcasses. Am J Vet Res. 2012;73:91–97.
5. Gebreyes WA, Bahnson PB, Funk JA, McKean J, Patchanee P. Seroprevalence of Trichinella, Toxoplasma, and Salmonella in antimicrobial-free and conventional swine production systems. Foodborne Path Dis. 2008;5:199–203.