Porcine Ear Necrosis
Thursday, March 19, 2026
New research identifies the cause
By Matheus Costa
Since at least the 1960s, porcine ear necrosis (PEN) – also known as ear-tip necrosis – has puzzled veterinarians and producers worldwide. This condition, described as progressive rotting of the ears of pigs, affects the growth performance of affected pigs, is a gateway for secondary infections, is painful and can be perceived as poor caretaking of the animals. Despite its global prevalence, the exact cause of PEN was unclear – until now.
A recent study by researchers at the University of Saskatchewan provided the first clear evidence on the cause of PEN: A bacterium called Fusobacterium necrophorum.
Why ear necrosis matters
Producers know ear necrosis all too well:
- The tips or corners of the ears turn dark a few weeks into nursery;
- Scabs form;
- Chunks of the ear fall off;
- In severe cases, a large portion or the whole ear is lost.
These wounds are not fatal, but they slow down weight gain. Recent research shows that sick pigs don’t gain weight as fast as the others. This results in production batches with pigs of different sizes.
University of Saskatchewan photo
People who experienced necrosis (gangrene, or rotting) have described it as excruciating pain, often worse than it looks. Pigs go through the same experience, likely feeling a lot of pain.
The rotting ears are a door for other infections. These infections may cause sickness, which may only be found at slaughtering in the form of abscesses – a common cause of carcass condemnation or demerit.
Finally, pigs with PEN may become disfigured as they lose parts of or their entire ears. This reflects poorly on us, as an industry, as it may be perceived by the public as a lack of care or poor husbandry.
Controlling PEN is important. But how?
Until now, the exact cause has been debated but never found. Poor ventilation, tail and ear biting, mycotoxins, trauma, Porcine circovirus, E. coli, Treponema, and various other microbes have all been suggested as the cause. But solid experimental evidence was limited.
What was found in this study?
Researchers conducted controlled trials using healthy pigs from a farm with no history of PEN. They inoculated pig ears with two bacteria previously suspected in PEN cases:
- Staphylococcus hyicus;
- Fusobacterium necrophorum.
The results were striking:
- Pigs inoculated with S. hyicus showed no lesions suggestive of PEN;
- Pigs inoculated with F. necrophorum developed classic PEN lesions, including tissue necrosis and partial ear loss, within days.
F. necrophorum was recovered from affected ears. The study was repeated, independently, and the same results were found – confirming F. necrophorum as the primary cause of PEN.
Five things you should know about F. necrophorum:
- Most pigs get it at farrowing, or immediately after;
- It will not cause disease until the conditions are right;
- It’s part of the normal gut microbiome;
- It does not survive for long on clean surfaces, but it can thrive in feces and rotting matter;
- It is hard to grow in the lab.
Why is this study important?
This discovery breaks the previous dogma that PEN is not an infectious disease, changing how we understand and manage it.
Until now, the condition was thought to be multifactorial, linked to environment, behaviour, and possibly viruses or mycotoxins. While these factors may still influence severity, the study shows that skin damage combined with F. necrophorum infection is the key trigger.
Implications for producers and veterinarians
1. Preventing skin trauma
PEN often starts after ear biting or other local injuries. Reducing aggressive behaviours and improving pen design can help minimize skin breaks that allow F. necrophorum to invade. Is there enough feeder and loafing/escape space?
University of Saskatchewan photo
2. Biosecurity and hygiene matter
F. necrophorum is part of the normal gut microbiome in pigs, meaning it’s already present in most barns. It’s unlikely we can eliminate it. The challenge is preventing it from entering wounds. Since it's present in feces, ensuring pens remain clean and that the proper dunging area is used will help minimize exposure of injured ears to F. necrophorum.
3. Treatment strategies may shift
Current approaches often rely on antibiotics, but without a clear target. Knowing the cause of PEN allows veterinarians to tailor the antibiotic treatment to this agent. It also opens the door for non-antibiotic solutions, such as vaccines or topical treatments.
4. Welfare
PEN is painful and visible. Addressing its cause improves welfare and reduces negative perceptions of husbandry practices used in the industry.
What’s next?
The research team is working on tools to prevent and treat PEN without relying on antimicrobials. This includes vaccines and management protocols tailored to reduce infection risk.
Take-home message
For the first time, science has pinpointed Fusobacterium necrophorum as the cause of porcine ear necrosis. Most pigs have this bacterium, as they get colonized during farrowing. This break- through gives producers and veterinarians a clear target for prevention and treatment, paving the way for better animal welfare and more sustainable production. BP