Antimicrobial Stewardship in pig health management

Antimicrobial resistance (AMR) is a global concern, for both animal health and public health. Estimations of the burden of AMR predict that 10 million people will die annually in 2050 when no action is taken now. Many resistant bacteria (or resistance genes) can cross species barriers, and therefore exchange of resistant bacteria and resistance genes between humans, animals and the environment occurs frequently. Most obvious is the transfer of AMR from animals to humans with food-borne pathogens such as resistant Salmonella spp. (e.g. S. Typhimurium DT104) and Campylobacter spp. (e.g. fluoroquinolone resistance). Regarding livestock-associated methicillin resistant Staphylococcus aureus (LA-MRSA), there is common sense that occupationally exposed people have a considerable chance to test positive for LA-MRSA. For transfer of other resistance markers (e.g. Extended Spectrum Beta-Lactamases) the extent of transmission between animals and humans is more difficult to quantify as this is not simply dependent on the transmission of bacteria but also dependent on the transmission of plasmids containing the resistance genes. These plasmids can change their host bacterium and transfer from for example E. coli type A to E. coli type B. The gut is considered to be an ideal place for bacteria to exchange genetic information. In the Netherlands, following the One Health approach, a consortium combined all recent ESBL-data from humans, animals and the environment. Following complex analysis techniques and taking into account genes, plasmids and the host bacteria, this study shows that about one-third of ESBL producing E. coli isolated from humans in the Netherlands, is of non-human origin. There is considerable human-to-human transmission but there is still a considerable influx of resistance into the human domain from other sources such as animals. It should be noted however that this study concerns only a specific type of resistance in a very specific context (a highly developed country at a time when veterinary antimicrobial use (AMU) was decreasing and human AMU already very low). Furthermore, these are estimates because transfer of AMR is very complex. Nevertheless, it is evident that actions should be undertaken to reduce AMU both in the human healthcare and in animals. 

AMR is currently high on the political agenda. After the publication of the WHO-Global Action Plan and the adoption of the resolution on containment of AMR by the General Assembly of the United Nations in 2016, countries were requested to prepare a National Action Plan (NAP) with a One Health approach to combat the emergence of AMR. A One Health approach is generally considered essential for the containment of AMR, however, hardly half of the countries has this One Health component in their NAP which underlines the urge for action. Initially ‘’One Health’’ was mainly restricted to humans and animals, but more recently also the environment has been recognized as an important domain. The environment can be a reservoir of resistant microorganisms and resistance genes spilling over from humans and animals. However, the environment can also be polluted with antimicrobials (residues) via feces and urine of animals and humans that are under treatment, and from pharmaceutical factories with poor measures to prevent environmental pollution (e.g. via waste water). These residues can select for resistant organisms that can further spread of in the environment. 

One of the 5 pillars of the WHO-Global Action Plan requests for the implementation of surveillance systems for AMR and AMU in all countries worldwide. Several countries have a reliable system implemented but there are clear gaps in data collection, in particular in Low and Middle Income Countries (LMICs). Therefore, there is limited information about AMU and AMR, particularly in these LMICs. Given the often unrestricted availability of antimicrobials without veterinary prescription and poor sanitation practices, especially in rapidly growing economies with intensive livestock sectors, AMR is assumed to be high, which is confirmed by data from case-studies. With the global trade of food products and travel of people, it is of high importance to develop interventions for AMU and AMR in all countries around the globe. 

An important tool for risk management is the so called WHO (World Health Organization) CIA list (Critically Important Antimicrobials for Human Medicine). This list ranks antimicrobials according to their importance for human medicine. Five antimicrobials are in this list ranked as ‘highest prioritized critically important antimicrobials’ (polymyxins, 3rd/4th generation cephalosporines, glycopeptides, quinolones and macrolides/ketolides). These antimicrobials should not be structurally used in animal production, for example for the purpose of prevention or growth promotion, and only be used in individual cases after susceptibility testing has shown that there are no feasible alternatives. Over the past years, actions in European countries to curb AMU have shown to be effective with a 32.5% reduction in sales ofantimicrobials for animals between 2011 and 2017 in 25 European countries. Recently there is new European legislation introduced with the aim to further control the development of AMR in animals.

Initiatives to reduce veterinary AMU in the Netherlands already arise from 2008. In the presentation, the actions undertaken to reduce veterinary AMU in the Netherlands will be presented with an emphasis on pig farming. One important intervention is the introduction of a benchmarking system for AMU at the level of individual farms and veterinarians. These actions have led to an almost 60% reduction in AMU in pig farming. New initiatives are currently aiming to reduce AMU via tailored interventions on the higher than average antimicrobial users which are identified through the benchmarking system. 

Nowadays AMU/AMR is high on the political agenda of national and supranational organizations. There is, however, still a considerable gap between policy and practice. Changes are urgently needed at practical level but this will only occur when there is a political will. It is therefore of utmost importance to use the currently existing political momentum to change the way we are exposing humans, animals and the environment to antimicrobials.