Denmark began implementing its plan to reduce the spread of PRRS five years ago. At the start, the situation was considerably more challenging: in early 2022, only 32% of sow farms and 15% of finishing farms were PRRS-free.
By mid-2026, the share of farms with negative status had increased to 74.3%.
Denmark applies a strict definition of “PRRS-free”: pigs must have no detectable antibodies to either field or vaccine virus. Accordingly, once a farm achieves this status, it no longer uses modified live PRRS vaccines.
This also means that replacement gilts brought in from outside or reared on the farm remain immunologically naïve to the PRRS virus.
From 5,800 Production Sites to 4,258
A distinctive feature of Danish pig production is the widespread use of multi-site production systems, in which sows, piglets and finishing pigs are kept at separate locations. Each production site has its own registration number.
At the beginning of the programme, Denmark had around 5,800 such production sites.
According to Bjørn Lorenzen, veterinarian and national coordinator of Denmark’s PRRS control plan, the number had fallen to 4,258 by mid-2026, of which 3,165 had already achieved PRRS-free status.
The fastest progress was made during the first years of the programme. The pace has now slowed because farms where virus elimination was relatively straightforward have already completed the process. At the same time, a significant number of farms remain at different stages of eradication.
How a Farm Achieves PRRS-Negative Status
As of mid-2026, around 3% of Danish pig farms have “under restructuring” status.
This stage lasts at least six months. The farm stops vaccinating against PRRS, after which a group of young replacement gilts that have not previously been exposed to the virus are placed in close contact with adult sows.
The procedure is repeated six months later.
If no antibodies to the virus are detected in the young animals after two such contact cycles, the farm can be granted PRRS-negative status.
On breeding farms, monitoring is carried out every six months. So-called sentinel replacement gilts are used to determine whether the virus is still circulating within the herd.
The Country Was Divided into Regions for Coordinated Control
One of the key elements of the Danish model has been its regional approach.
At the beginning of the programme, the country was divided into 58 regions. As the number of PRRS-free farms increased, the number of such zones was reduced to 21.
The logic is straightforward: producers within the same region should coordinate their actions as closely as possible. If most farms in a given area eliminate the virus, the risk of reinfection from neighbouring farms is reduced.
Regional coordinators play an important role in this system. Denmark has nine in total.
One of them is Mads Weidtløv, who works for the agricultural consultancy Fjordland in north-western Denmark and is responsible for four regions.
The coordinator maintains a database containing the health status of all pig farms in the assigned area. The information is updated every 24 hours. Once laboratory results are available, the veterinarian submits them to the regional coordinator, who verifies that the data have been entered correctly.
The Status of Every Farm Is Visible to Other Producers
Transparency has become another important element of the programme.
Every six weeks, producers receive an overview of the PRRS situation in their region. The document shows the name and status of every farm.
In addition, around five times a year, coordinators send newsletters to producers with updates on progress in controlling the virus and information on the next steps.
Regional coordinators also hold meetings with producers and veterinarians, explain how the programme works and encourage farms to participate.
This level of transparency also creates a degree of peer pressure. When most neighbouring farms are working to eliminate PRRS, it becomes increasingly difficult for individual producers to remain outside the programme.
Pig Movements Are Controlled According to Regional Status
Another important tool is the control of animal transport.
Pigs from regions with a relatively high proportion of PRRS-positive farms are not allowed to be moved into areas with a low infection level.
The most challenging situation currently remains in the Salling region in north-western Denmark, where 47% of pig farms are still PRRS-positive.
The opposite example is the island of Bornholm, where around 500,000 pigs are produced annually.
Since March 2025, the island has been completely free of PRRS. Virtually no live pigs are imported there: one local producer supplies other farms with F1 replacement gilts, allowing the island to maintain a closed production system and reduce the risk of reintroducing the virus.
Determining PRRS Status Has Become Mandatory
Producer participation in the programme is largely voluntary, but the government has introduced mechanisms that encourage farms to establish their status.
The Danish Veterinary and Food Administration adopted regulations making it mandatory for farms to determine their PRRS status.
Despite this, the status of around 1.7% of pig farms remains unknown. In some cases, these may be empty farms or producers that, for various reasons, do not participate in blood monitoring.
At the same time, the industry expects economic incentives to gradually encourage these producers to participate. In particular, if processors begin paying lower prices for PRRS-positive pigs, remaining outside the programme will become economically disadvantageous.
Each Farm Has Its Own Eradication Strategy
Another reason for Denmark’s success is the absence of a one-size-fits-all approach.
The programme provides for an individual PRRS eradication strategy based on the production structure and epidemiological situation of each farm.
Vaccination is initially used to reach a point where sows stop shedding the virus. At the same time, piglet facilities are cleaned and disinfected.
Depending on the situation, full or partial depopulation followed by repopulation may be used.
Danish veterinarians have many years of experience with such methods and carry out these procedures dozens of times each year.
Why the Danish Model Works
Over five years, Denmark has significantly reduced the spread of PRRS through a combination of mandatory farm-status determination, data transparency, regional coordination, control of animal movements and individual eradication programmes.
Another important factor is producers’ own awareness of the economic benefits of maintaining a high herd-health status.
Although the easiest stage of the programme has already been completed and further progress is likely to be slower, the mid-2026 result — 74.3% of farms being PRRS-negative — demonstrates that a systematic regional approach can substantially improve the epidemiological situation even for a disease as difficult to control as PRRS.
PigUA.info, based on materials from foodagribusiness.world