Analysis of antimicrobial use

Analysis of antibiotic use

What we do


The task of the 'Data Analysis Unit' of AMCRA is to both analyse and report data relating to antibiotic use in animals. The focus of its work is currently on antibiotic use at farm level and in livestock (pigs, chickens, cattle).

In practice, antibiotic use notifications collected in external data collection systems are processed according to a specific methodology, to benchmarking reports for farmers on the one hand and summary reports for the sectors and the Government on the other hand.


Periodic benchmarking reports
These are geared towards individual farmers and veterinarians.

Benchmarking reports for farmers describe and benchmark the use at a specific farm. The farmer and veterinarian(s) in question are provided with information about antibiotic use at the farm on the basis of the indicator TD100 (number of treatment days per 100 days, see further on this page). An essential aspect of this is the objective comparison with other farms (= benchmarking). The reports also contain qualitative data, for example regarding use of different types of antibiotics, based on their importance for animal and public health indicated by the AMCRA colour codes.

Benchmarking reports for veterinarians provide information about the extent to which a veterinarian prescribes, purchases or administers antibiotics. This information is based on two scores. The contract score is an indication of how well farms with which the veterinarian has a contract for veterinary services has scored in the farmer benchmark. A veterinarian is benchmarked on the basis of this contract score. The management score indicates the extent to which the veterinarian has purchased antibiotics in the capacity of a farm veterinarian. The benchmarking reports for veterinarians also include qualitative information.


Summary reports
The summary reports use the data gathered at farm level to describe antibiotic use within a given period at a higher level, for example for a specific sector or for a group of livestock associated with a particular quality label. Striking and/or important trends over longer periods are identified, monitored, and interpreted.

 

The performing of analyses and production of reports form the end-point of a detailed set of processes, such as the import and exploration of data, and data management, verification and validation. These processes are developed and refined according to the specific needs, questions, and insights. These processes are automated as much as possible. 

The analysis and reporting of antibiotic use plays an important role in achieving the 4 strategic objectives of AMCRA. After all, "measuring is knowing": detailed information in the form of 'bespoke' reporting of antibiotic use at farm and sector level can be used in order to address and monitor (excessive) antibiotics use in a targeted way. The Data Analysis Unit therefore plays a crucial role in communication to users and suppliers of antibiotics and awareness-raising among these target groups.

In addition to its core tasks of analysis and reporting, the Data Analysis Unit also provides support and advice in the development and operation of the various data collection systems in Belgium concerned with antibiotic use in veterinary medicine, and it is involved in a number of (inter)national projects relating to quantification of antibiotic use in animals.

Clients


The Data Analysis Unit is available to perform analyses for all (owners of) data collection systems of antibiotic use in animals. Through regular consultation, we aim to achieve optimum cooperation with our clients and the managers of data collection systems. 

Currently, the Data Analysis Unit of AMCRA performs analyses on behalf of the Belgian Federal Agency for Medicines and Health Products, using the data collected in 'Sanitel-Med' (for pigs, laying and broiler hens, and veal calves), and on behalf of the 'Begrotingsfonds voor de gezondheid en de kwaliteit van de dieren en de dierlijke producten', using the data collected in 'AB Register' (for pigs, poultry and dairy) and 'BIGAME' (for dairy).

 

Sanitel-Med

The indicator TD100


Antibiotic use can be expressed in a few different ways. As a basic rule, a good indicator consists of a numerator(= the number of 'technical units' used) that is standardised using a denominator(= the mass of animals).

The annual total quantity of antibiotics for animals sold in Belgium, for example, is reported in mg of active substance per kg of biomass. This is a 'weight-based' method of calculating antibiotic use, given that weight-based technical units (mg) are used.

Another method is determining animals' level of exposure to antibiotic use. This method is based on determining the treatment incidence (Timmerman et al., 2006, Prev. Vet. Med., 74, p. 251-263). Calculating the TD100 is one example of this. The TD100 is the number of Treatment Days using antibiotics per 100 days. In other words, the % of treatment days on which antibiotics were used. This is a 'dose-based' indicator, where the number of doses is the numerator. 

THE PRINCIPLE OF CALCULATING THE TD100

To calculate the TD100 the quantity of antibiotics used is divided by
- the DDDAbel or Defined Daily Dose Animal defined for Belgium 

- the total mass of animals that was at risk of treatment (average number of animals present multiplied by the estimated mass at the time of treatment)

- the total number of days that an animal was at risk of treatment.

Some products have a longer duration of action. The LA-factor or 'Long Acting-factor' adjusts for this extended duration of action. After all, one day of treatment with a long-acting product must be counted as more than one treatment day.

Formula for calculating the TD100:

 

THEREFORE:
Antibiotics for which the package leaflet recommends a small dose are weighted equally in the calculation with antibiotics for which a high dose is recommended.

AND: large farms are levelled to small farms.

AND ALSO: regardless of which period at risk is under consideration, the antibiotic use is converted into 100 days.

IN OTHER WORDS:
Antibiotic use at each farm is calculated in a standardised way, which allows for a valid comparison of farms.

DEFINED DAILY DOSE ANIMAL

Generally speaking, there are several different dose-based 'technical units' for expressing the quantity of antibiotics used, such as the defined daily dose (DDD), the used daily dose (UDD), and the defined course dose (DCD). In order to distinguish between the units used in human medicine and those in veterinary medicine, we add an 'A' (for 'animal') for the latter case.

To calculate the TD100, we use the DDDA used in Belgium, the DDDAbel. These values are defined for each individual product, based on the information given in the 'summary of product characteristics'. The same applies for the LA-factors, the LAbel. Further explanation about the methodology used to define the DDDAbel and the LAbel can be found in the documents that are available to download below.

 

The antibiotics dose lists for each species for which AMCRA is currently preparing benchmark reports (pigs, chickens, veal calves) can be found below. These include the DDDAbel and LAbel defined for all products. The antibiotic dose lists are updated regularly and were last updated in June 2021.

Benchmarking


Farmers

Benchmarking of farmers is carried out by comparing their antibiotic use, specifically their average TD100 value during the benchmarking period, with one or two TD100 threshold values. This is done for each animal category. The benchmarking period is usually one year for pigs, poultry, and dairy, and two years for veal calves. The result is a benchmark score and a classification as a low user (green colour score), intermediate user (yellow colour score) or high user (red colour score). This is shown in the graph below. Farmers who are classified in the red zone repeatedly or over the long term are regarded as alarm users and are assigned a purple colour score.

In the first phase, we are working with dynamic threshold values, which change in each benchmarking report. This is because the values are recalculated for each new benchmarking report. Two threhold values are typically used: the TD100 value delineating the 10% highest users is the upper threshold value. The TD100 value delineating the 50% lowest users is the lower threshold value. Working with dynamic threshold values allows for an insight into how the sector is developing as a whole, while also identifying the farms with the highest antibiotic use in a representative way. The disadvantage of this method, however, is that farmers can never be sure what to expect in the next benchmarking report.

For this reason, Belgium is switching over to interval limit values in the second phase. These limit values are maintained for a longer period: the interval. The duration of the interval depends on the overall antibiotic use in the sector, the antibiotic use in other animal categories, and the lower and upper threshold values themselves.

At present, dynamic threshold values are only being used in the dairy sector. Data collection in this sector began in 2018 and the first benchmarking report for dairy farmers was published in 2019. 

Belgium will only switch over to interval limit values once there is a sufficiently clear picture of (the evolution of) antibiotic use in a sector. This is already the case for the pig, poultry, and veal calf sectors, whose antibiotic use has already been mapped out for several years now, and communication has been established with farmers and veterinarians in these sectors via the benchmarking reports. In these sectors, the interval limit values form part of the sector-specific reduction targets that were established in the AMCRA 2024 plan and that were defined in more detail in consultation with the sectors in late 2020.

The sector-specific reduction targets consist of the TD100 threshold values that came into effect on 1 January 2021 and gradually decrease over time, with an initial adjustment scheduled in 2023 and a provisional final adjustment in 2024. This creates a reduction pathway for each sector, and it is already clear to all farmers at the outset what requirements they will need to comply with. The reduction pathways will be monitored annually in order to assess feasibility against the situation in practice.

It is also possible to perform benchmarking for the AMCRA colour codes (yellow, orange or red) that are assigned to antibiotics (see second graph below). 

Figure: Principle of benchmarking using two limit values.

Figure: Example of division of the number of treatment days by products with their various AMCRA colour codes.

 

All procedures used by AMCRA for calculations, verifying and monitoring the data quality, benchmarking, and reporting on antibiotic use in animals at farm level, based on data gathered in Sanitel-Med, are summarised in a Standard Operating Procedure.

 

Veterinarians

The methodology for benchmarking veterinarians is based on the AMCRA recommendation 'Benchmarking and monitoring antibiotic use in animals – part 2: veterinarians'.

Benchmarking is performed using a Contract Score (CS), a figure out of 100, which indicates the benchmarking results of a veterinarian's 'contract farms'. A 'contract farm' in this case is defined as a farm with which a veterinarian had a contract for farm veterinary services for at least half (= 183 days) of the benchmark period (= one year). The higher the antibiotic use on the contract farms, the higher the CS, and vice-versa.

In the same way as for farmers, two threshold values are defined for the CS, which divide veterinarians into 50% 'low suppliers', 40% 'intermediate suppliers', and 10% 'high suppliers'.

Figure: The benchmarking of veterinarians based on the Contract Score and two threshold values.

In addition to the contract score, a Management Score (MS) is calculated for each veterinarian. This too is a figure out of 100 and it reflects the extent to which a veterinarian has prescribed or purchased antibiotics in the capacity of a farm veterinarian. A 'farm veterinarian' in this case is defined as having a contract with the farm in effect on the date on which the antibiotics were purchased. Benchmarking takes account of all farms for which the veterinarian reported antibiotic use at least once during the benchmarking period; these farms may or may not be contract farms. A high MS indicates that the veterinarian primarily purchases or prescribes as a farm veterinarian.

Sector-specific TD100 threshold values


Barometer Antibiotic Use


Every quarter, FAMHP and AMCRA publish the 'Barometer Antibiotic Use', based on the mandatory recording of antibiotic use in Sanitel-Med. In a few graphs, the main trends relating to antibiotic use per species (pigs, poultry, veal calves) are illustrated. 

The figures show the development of total annual use in each species on the one hand, which shifts each time data from the last quarter is added. In addition, four key veterinary antimicrobial families are highlighted, namely polymyxins (colistin), zinc oxide premix for pigs, and the two families with a red AMCRA colour code, namely (fluoro)quinolones and third- and fourth-generation cephalosporins. For reference, the barometer also always includes the quantity in metric tonnes or kilograms that have been purchased in Belgium according to the most recent BelVet-SAC sales data.

It should be noted that the figures shown are not normalised on the basis of biomass, but are expressed in absolute figures (metric tonnes, kg). In view of the fact that biomass typically varies for each species by a few per cent each year, these 'barometer' figures are not intended as a reference for antibiotic use in the various species. 

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Centre of Expertise on Antimicrobial Consumption and Resistance in Animals

Latest results

Belgian report on veterinary national antibioticum consumption and on farm-level use - 2020
First "One Health" report on AMU and AMR