Background and history

This is a sporadic disease seen in newborn pigs. Usually more than one pig is affected in a litter. The tremor is only seen when piglets are walking around and not when they are asleep. The condition decreases with age but if the tremors are too great for the piglets to find a teat and suckle then mortality maybe high.

Mortality in an affected litter or in a herd outbreak could increase above the norm by 3 to 10 percent.

It would be unusual to find a pig farm that had not experienced one or more litters of trembling piglets, yet little disease is seen in most herds, presumably because an immunity is established in the sow herd. In new gilt herds however, there can be major outbreaks involving up to 80 percent of all litters during the first parity. This is an unquantifiable risk in any new gilt herd.

Clinical signs

• Muscle tremor of the head and body.
  • Only seen when piglets are walking around and not when they are asleep.
• Other nervous symptoms.
• Splay leg.
• Incoordination.
• Often dog sitting.
• Increased mortality.
  

Diagnosis

This is based on clinical evidence although histological examinations in the laboratory can help to differentiate the groups.

Causes

The causes of the condition are classified into four groups based on brain histology:

1. Associated with a classical swine fever.
2. Possibly associated with a recently recognised circovirus and involving both circoviruses types 1 and 2 simultaneously. Most of the problems in the field are found in this group.
3. Associated with either hereditary disorders seen in the Landrace or Saddleback breeds or with organophosphorus poisoning.
4. Includes aujeszky's disease and Japanese encephalomyelitis (JE) virus.

Prevention

• Attempts to immunise breeding stock should be carried out. The following may assist and the results should be documented for further studies where litters are continually affected.
• If there is a history of the disease on the farm expose incoming maiden gilts to faeces from older animals and boars for 4 to 6 weeks prior to mating.
• At the time of mating use tissue paper to wipe around the prepuce of the boar and the vulva of the mated sow. Expose the group of maiden gilts to the tissues. Do this 2 to 3 times weekly.
• Maintain a continuously populated gilt pen when gilts first enter the farm to ensure continual exposure to any viruses. (You would need to make sure however there is no build up of parasites in this pen.)
• Assess the results of using a vasectomised boar from one your affected litters for a period of six weeks prior to full mating.
• Move all maiden gilts into the main mating area for a period of seven days commencing at least four weeks before mating is due to start to expose them to any possible infectious agents.

Treatment

• There is no specific treatment for affected piglets but careful management will greatly reduce mortality.
• Ensure that piglets are given colostrum at birth and assisted to a teat.