The inspectors wanted to rule out an infectious process causing such lesions. The farm veterinarian said the piglets started with lesions at the tip or base of the ear.
These findings are suggestive of a case of necrosis of the tip of the ears which progressed and finally ended in necrosis of the entire pinna. Usually cannibalism phenomena occur amongs piglets when initial lesions appear. If it had been something infectious which caused cyanosis and subsequent necrosis, usually lesions would be bilateral and often other signs and lesions would have been observed. It seems likely that there was an initial lesion (trauma or cannibalism) and subsequent cannibalism, but at slaughter only a scar can be observed. Anyway, a congenital malformation is ruled out.
The necrotic ear syndrome (or ulcerative spirochetosi of the the pinna) has been described which begins with a skin lesion that could be infected with Staphylococcus hyicus initially and with more virulent spirochetes or streptochoccus. Lesions by Sarcoptes scabiei could also start the process.
Up to 80% of the animals in a penn coud be affected with unilateral or bilateral necrotic lesions wich, if extensive, may end up with complete disappearance of the pinna.