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Fewer antibiotics, more hygiene

14/2004, 12.11.2004

Risk assessment proposals to control antibiotic-resistant germs in animal herds

How can one limit the development and spread of antibiotic-resistant microorganisms in animal husbandry? This is the key issue at the Symposium “Risk Management for the Limitation of Antiobiotic Resistance” to be staged in Berlin on 15 and 16 November 2004. It is organised by the Federal Agency for Consumer Protection and Food Safety (BVL) in cooperation with the Federal Institute for Risk Assessment (BR) and the Federal Agricultural Research Centre. This Symposium follows on from the international symposium “Towards a Risk Analysis of Antibiotic Resistance” staged last year at BfR. “After scientifically assessing the risk of the antibiotic resistance of zoonosis pathogens in animal husbandry last year, we are now going to discuss the recommendations drawn up there for the limitation and avoidance of antibiotic resistance in Germany” commented the President of BfR, Professor Dr. Dr. Hensel. This was how he outlined the content of the Symposium which starts on Monday.

At the event last year experts agreed that immunity to antimicrobial substances is spreading amongst bacteria. This is of particular relevance for those bacteria which use the animal as the host and can trigger disease in man. This development was observed particularly in studies about salmonella and campylobacter strains. Both bacterial strains mainly reach man via the food chain. Patients infected with resistant pathogens had a higher risk of dying in the course of the following two years than patients infected with pathogens sensitive to antibiotics. Another problem is that germs occurring in animals can exchange their resistance genes (hereditary factors which render them immune to antimicrobial substances) with pathogens which are of importance in man.

Factors that contribute to the selection and spread of resistant bacteria in animals are,

  • mass medication of entire herds
  • sub-therapeutic dosage of antibiotics
  • lengthy antibiotic treatment
  • the use of antibiotics with a broad spectrum in animal husbandry and
  • their prophylactic and metaphylactic use

Up to now, it was not possible to estimate the extent to which the use of antibiotics in animal husbandry contributes to the development of resistance of infectious germs in man. It is generally accepted that resistant germs can be transmitted via foods and products of animal origin to man. The experts have clearly outlined the potential risks: besides infections which may take a fatal course, they mainly involve a longer duration of illness for patients, the need for hospitalisation and the risk of becoming susceptible to other dangerous infectious diseases as a consequence of a weakening of the body’s own defences.

“Experts estimate that around 250 cases of salmonellosis occur every year in Germany for which the necessary antibiotic treatment is no longer effective.” Around 10 percent of these infections have a fatal course”, was how Professor Hensel described the situation. There is particular concern about the number of bacterial strains that are multiresistant, i.e. are immune to several antibiotics.

From the angle of risk assessment, this trend should be countered by a package of measures. The first recommended option involves measures that help to generally limit the use of antibiotics. In the field of animal husbandry they include improved husbandry conditions. Particularly where large numbers of animals – for instance chicken, turkey and pig production – are kept on a small area, animal health must be improved in preventive terms by means of corresponding hygiene and vaccination measures. Furthermore, antimicrobial substances should be used in a more targeted manner in animal production. In plain English this means that it must first be established which pathogen is present in the herd and to which antibiotic it reacts. Priority should be given to the precision weapon here of the carefully selected and suitable active substance over the shotgun of the broad-spectrum antibiotic.

In principle, modern highly efficacious substances, which are also used in human medicine like fluoroquinolones and cephalosporins of the third and fourth generation, should only be used to treat individual animals. These treatments should also only be administered in the case of strict indications and these medicinal products should only be given if the pathogens are resistant to other antibiotics. Consideration should also be given to whether really new antibiotics should no longer be authorised for use in animal medicine.

These proposals of BfR and other national and international experts will be critically examined at the Symposium with regard to their suitability for incorporation into practical measures.