Porcine Ear Necrosis: From Outside /In or Inside / Out? By George Charbonneau from South West Ontario Veterinary Service

Porcine ear necrosis (PEN) has been a problem in pig production since it was first described in the mid 1980’s. Careful observation will reveal that PEN is initially associated with raised red areas of inflammation visible in the epidermis (surface) of the skin at the extremities of the ear. These small lesions may resolve on their own or they may continue to increase in size and eventually will join up to cover a significant portion of the ear extremities. The surface layers of skin become encrusted and ulcerated. Portions of the ear tips may be lost. The exact cause and pathology of PEN can be difficult to nail down in controlled trials. There have been a number of explanations for PEN that have been offered over the years. Skin infections, systemic infections leading to vasculitis, ear biting and mycotoxins (eg Ergot) have been suggested in the past. Previous explanations could be roughly divided into two camps. One camp suggests that the lesions begin with damage of internal issues ( eg infection / vasculitis) or with an issue with mycotoxins such as ergot. Basically suggesting that PEN begins internally and works its way to the outer layers. The second camp supports the idea that the lesions start in the outer layers of the skin and gradually work their way deeper. These Belgian researchers wanted to take a deeper dive on the role of oral manipulations (biting and nibbling) in the occurrence of PEN in nursery pigs. A convenience sample of three farms that were known to be affected by PEN were visited weekly. Prevalence and severity of PEN was recorded and video recordings allowed the researchers to assess pig behaviour.

These researchers found the following:

• No severe PEN lesions were recoded in the farms in this particular study but some individual pens had lesion prevalence as high as 58% to 93% of pigs affected.
• No lesions of PEN were detected at weaning and in most cases the prevalence of lesions increased over time before gradually starting to decline.
• Ear lesions tended to occur about 1 to 2 weeks after the increase in the number of ear manipulations (chewing and nibbling).
• Frequency of oral ear manipulation behaviour significantly differed (P < 0.05) between pigs in pens with high and low PEN prevalence with increased ear manipulation behaviour being significantly related to a subsequent increase in PEN lesions (OR = 4.3; P < 0.001). (OR = Odds Ratio)
• Metagenomic investigation of lesion scrapings revealed a variety of pathogens.Some of these pathogens were likely to be “innocent bystanders” and some were known to opportunistically cause skin lesions when skin is damaged or wet.
• Microscopic tissue lesions were primarily located in the epidermis (outer layers) of the skin and not initially in the deeper internal tissues.