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Assessment of the transfer of antimicrobial resistance between pets and humans in Norway
Assessment of the transfer of antimicrobial resistance between pets and humans in Norway
Foto: iStock Photo
In 2014, the Norwegian Food Safety Authority (NFSA) requested an assessment on the transfer of antimicrobial resistance (AMR) between pets and humans from VKM. VKM appointed a working group consisting of members of the Panel on Biological Hazards and one external expert to prepare the answers to the questions posed in the Terms of Reference (ToR).

One member from the Panel on Animal Health and Welfare contributed as a hearing expert. The Panel on Biological Hazards has reviewed and revised the draft prepared by the working group, and the assessment has been adopted.

AMR can be described as the ability of a bacterium to withstand the effects of an antimicrobial (Abbreviations and glossary).

Resistance to antimicrobial agents may be intrinsic or acquired. Intrinsic resistance is a natural property of an organism resulting in decreased susceptibility to a particular antimicrobial, whereas acquired resistance is a result of genetic changes in an organism due to mutation or the acquisition of extra-chromosomal genetic material.

AMR is a major threat to human health; not only is it a threat to the control of bacterial diseases, but it is also a threat to modern medicine in general. To date, AMR has been described for all known antimicrobials currently available for clinical use. Use of antimicrobials inevitably has resistance development as a side effect, and therefore all categories of antimicrobial use should be evaluated, including use of antimicrobials for humans, production animals, companion animals, and plants.

Increasing amounts of antimicrobials are used for treatment of pets, including numerous substances used in human medicine. The main bacteria of concern include Staphylococcus pseudintermedius and Escherichia coli, as well as other organisms of clinical importance in human medicine, such as methicillin-resistant Staphylococcus aureus and Enterobacteriaceae spp. Transmission of such organisms occurs between pets, owners, and veterinary staff. Pets can act as reservoirs of these bacteria and their occurrence can impact on the use of antimicrobials in human medicine.

An increase in sales of antimicrobials marketed for companion animals of 19 % was observed in Norway between 1995 and 2014. This increase was mainly accounted for by penicillins, and approximately 87 % of the penicillin products sold for use in companion animals during 2014 was as a combination of amoxicillin and clavulanic acid.

According to the Norwegian monitoring programme for AMR in the veterinary sector, the frequency of resistance reported in pet animals has been stable since the start of the programme in the year 2000.

The nature of relationships between pet animals and their owners has changed considerably during the last decades, and today many pet animals commonly live as family members in the household in close contact with their owners. Interspecies transmission (in both directions) between pets and humans, and between pets and other animal species, can occur by direct contact or indirectly through environmental contamination of households, veterinary clinics, and public spaces.

In recent years, an increasing number of pet owners have become interested in feeding raw meat or fish to their pet dogs rather than commercial dry food. The increasing occurrence of AMR in bacteria in food-producing animals in Europe, and to a certain extent in Norway, means that raw meat provided to Norwegian dogs as feed represents a close contact between dogs and the domestic pool of AMR in Norwegian livestock and, to a certain extent, the international population of domestic animals.

Today’s travel with animals and relatively unregulated import, especially of dogs, exemplifies an open population. In addition, many dogs also travel, mainly inside the EU/ EEA due to the relaxation of regulations. Travel to areas with high endemic levels of bacteria with AMR has been indicated as a risk factor for the acquisition of such bacteria. Most studies have been conducted on human travellers, but there is no reason to believe that the microbiota of pets behave differently.

This means that the Norwegian dog population is in contact with the whole European population of dogs, with the long-term effect that the Norwegian human population will also be exposed to AMR patterns introduced to Norway by travelling dogs and dogs imported from other countries.

Probability characterization – answers to the questions

  • According to current knowledge S. aureus, S. pseudintermedius, and Enterobacteriaceae spp. are the bacteria of most concern regarding transfer of AMR directly between pets and humans. However, the literature is limited and evidence indicating the specific bacteria most likely to transfer resistance directly or indirectly between pets and humans is lacking.
  • Broad-spectrum antimicrobials, such as cephalosporins and fluoroquinolones, are traditionally associated with promotion of resistance. The extensive use of amoxicillin and clavulanic acid can promote the same type of resistance as cephalosporins. In addition, it is also known that even narrow-spectrum antimicrobials, such as phenoxymethylpenicillin, may induce and promote resistance in bacteria.
  • The register of prescriptions available to NFSA, issued by veterinarians and dispensed by pharmacies, was established earlier, but not all pharmacies participated in the register before 2015. It is thus currently impossible to extract reliable data on real consumption of human medicinal products (HMP) and veterinary medicinal products (VMP) in pet populations and to establish the extent to which antimicrobial drugs are used for pets.
  • The following factors have been identified as being likely to increase the development and dissemination of AMR to such an extent that the probability for direct or indirect VKM Report transfer of AMR between pets and humans in Norway should be regarded as non-negligible:

o Use of antimicrobials.

o Therapeutic use of antimicrobials in the Norwegian dog and cat populations.

o The Norwegian dog population being part of an open population with extensive international contacts.

o Use of raw pet food of animal origin.

  • Minimal veterinary use of critically important antimicrobials (CIA) licensed for human use only should reduce the development of the resistance to those antimicrobials.
  • Guidelines and education about the zoonotic risks associated with household pets can help to reduce the probability of transfer of AMR. Low awareness of primary healthcare practitioners about zoonoses transmitted by pet animals, and communication difficulties between veterinary and medical practitioners can lead to less timely diagnoses and identification of resistant strains. Providing sufficient space and attention to companion animal zoonoses in medical and veterinary university curricula, as well as in continuing education, can raise awareness and identify possible emerging resistant strains.
  • Clear diagnostic routines and reporting lines can lead to the development of a clearer picture on the existing prevalence of resistance in pet populations, and also provide information on possible pathways for spreading.