Veterinarians and producers used to worry about antibiotic resistance in that the effectiveness of medicines used to treat sick pigs may be reduced by overuse on the farm.
While this is still a concern, the “new” issue with antibiotic resistance is whether routine use of antibiotics on the farm will result in resistance of human pathogens that may have been acquired through a foodborne source.
Actually, the primary cause of the increase in resistance of human bacteria is not from farm use but from how human doctors (especially those treating children) prescribe antibiotics.
Recent surveys of prescribing practices by doctors reveal that children ages 0 to 4 years receive 53% of all antibiotic prescriptions. Most are for inner ear infections.
The majority of children have had three or more antibiotic prescriptions by the age of four, and many of those prescriptions were for children with colds, upper respiratory infections and inner ear problems.
Many or most of these problems were viral in nature, making the antibiotics unnecessary and certainly increasing the chances of developing antibiotic resistance in the bacteria present in those patients.
What Producers Can Do
Pork producers know that overuse of antimicrobials hurts their bottom line. To reduce the incidence of resistance on the farm, first make sure to follow all the regulations as they relate to antimicrobial use.
Your veterinarian knows and follows the regulations set forth by the Animal Medicinal Drug Use Clarification Act (AMDUCA) that spells out how to apply the use of antimicrobials on the farm. If the need exists for using an antibiotic in a manner that is not on the label (extra-label drug use), the veterinarian and the producer must adhere to certain rules and guidelines.
In addition to compliance with the law, Judicious Use Guidelines are set forth by the American Veterinary Medical Association (AVMA) in conjunction with the American Association of Swine Veterinarians (AASV).
These guidelines outline good production practices that will reduce the risk of developing antimicrobial resistance on the farm. Following the regulations of AMDUCA and the Judicious Use Guidelines will help to reduce the risk of resistance development.
A client called experiencing a sudden onset of watery diarrhea in his 1-day-old baby pigs. The pigs were unresponsive to therapy with the client's usual treatment.
This herd had a history of E. coli diarrhea that had, in the past, responded to treatment with the labeled dose of an antimicrobial approved for use in swine.
Upon bacterial culture of the feces of an untreated piglet, a strain of E. coli was confirmed as the cause of the diarrhea. An antimicrobial sensitivity test was performed on the strain of E. coli from the case and revealed that resistance to the antimicrobial previously used had developed.
We used the sensitivity pattern provided to the lab to choose a different antimicrobial that, according to the test, would be effective against the strain of E. coli identified in this case.
The antimicrobial choice required that I (as the attending veterinarian) write a prescription prior to its use on the farm. Prior to scripting this antimicrobial, I had to ask myself if any other antimicrobials with a food animal use label could be used.
Finding none, I needed documentation and laboratory confirmation that the drug of choice in this case was indeed the only effective medicine available. I also had to find adequate scientific data so as to establish a safe withdrawal time for the antimicrobial chosen.
After that, the medicine has to carry a label with clear and concise directions as well as any cautionary statements, withdrawal times and veterinarian's name and address. Having to do all this might seem like a lot of paper work, but it is the law.
The next step in this case was to discuss farrowing house hygiene before and during farrowing and what changes in the vaccination protocol might be helpful in reducing the incidence of E. coli diarrhea.
The last step was to follow up, making sure the prescribed treatment was working and there were no adverse reactions.
Retaining Antimicrobial Use
Antimicrobials are an invaluable tool to pork production. We must fight to retain the availability of these tools and demand that they not be removed from use without sound scientific proof of risk to human health.
Using these tools properly and judiciously, with compliance to the existing regulations and guidelines, is our best defense against loss of these valuable weapons against disease.