Over a period of almost 2 years, a progressive motor disturbance was found
to occur in 20-50% of the litters of both primiparous and multiparous sows
in a large pig herd of 1000 sows. The motor disturbance sometimes affected
the entire litter; however, in most cases only a few piglets per litter wer
e affected. The clinical signs appeared at 3-5 days of age and consisted of
difficult movement followed by anteflexion or retroflexion of the tarsal j
oints or 'rabbit-like posture'. Subsequently, primarily after weaning, infl
ammatory and necrotic lesions developed on the paralysed limbs as a result
of secondary infections of injuries. The tibial nerve and the common fibula
r nerve of recently affected (5- to 6-day-old) piglets showed degeneration,
demyelination and necrosis of some of the nerve fibres, accompanied by res
torative changes in more chronic cases. The central nervous system, bones,
skeletal muscles, tendons and joints showed no lesions that could have acco
unted for the symptoms of motor disturbance. Aetiological investigations ex
cluded the possibility of lead, copper and cadmium toxicity. Vitamin B-2 ad
ministered orally at 1 day old proved to be ineffective. The disease did no
t develop in piglets of sows kept at another farm under the same management
and fed a diet prepared according to an identical formula from the same in
gredients as those used on the affected farm, but with no milk whey added.
This raised the suspicion of triaryl phosphate (TAP) poisoning, but this wa
s found not to be the cause of the disease. New boars had not been brought
to the farm in the year preceding the onset of disease, and the disease cou
ld not be linked to a specific boar or boar line. The aetiology of the dise
ase has remained unclear.