Veterinary Services

Neurological disorders

Three piglets were submitted from an outdoor herd where three litters of piglets were affected with apparent congenital tremor. A few litters had been affected 14 weeks previously; in each case usually more than one pig per litter was affected. The condition was non-progressive and the pigs survived at least to weaning, when they were moved to another unit. Only gilt litters were affected and different boars were involved. No treatments, other than routine vaccinations, had been administered during pregnancy. One four-day-old piglet submitted showed constant severe muscle trembling and had a tendency to assume a "dog-sitting" position. This piglet was in thin body condition, but the other two affected piglets submitted from different litters were both in good condition and showed milder tremors. Histopathology of the most severely affected piglet showed hypomyelinogenesis of ventral aspect of the spinal cord at the level of C3. The lesions were consistent with a diagnosis of congenital tremor type AII. The cause(s) of this type of lesion is unclear but it is thought to be due to an in utero viral infection occurring at a crucial stage of spinal neurological development. Both unidentified enteroviruses and porcine circovirus 2 (PCV2) have been previously implicated in such lesions but the associations have not been proven.