Congenital Tremor



A variety of events, diseases, toxins etc can cause a piglet to present with congenital tremor


The most common cause is an unidentified viral agent


There are a number of genetic causes – Landrace trembles, Saddleback tremors


There are other known congenital infections for example Classical Swine Fever Virus which can result in the production of trembling piglets

This technical note will concentrate on the most common cause

Clinical signs

The problems classically occurs in naďve gilt litters from newly introduced stock.

New born piglets

Piglets are born trembling in all the muscles.  They may be unable to walk and often are unable to suckle efficiently.  Once attached to the teat by the stockman the piglet will suckle vigorously, but once let go by the stockman the piglet will often shake itself away from the teat.  Excluding sporadic cases it is normal that there will be an increase in pre-weaning mortality and diseases, in particularly overlaids, increased lameness from trauma and outbreaks of scour.  A trembling piglet which has problems suckling will clearly have problems ingesting sufficient colostrum.  Mortality rates of 75 to 100% are common.  Sometimes the trembling will be noticeably reduced when the piglet is asleep.

In the piglets which survive, the clinical signs subside with age. However, the tremble is often noticeable if the animal is watched over time and then relaxes, then mild muscle trembles (fasciculation) will be evident over the ears and muscles on the back.

Start up herds

The problem can be very severe and potentially disastrous with almost 100% of litters presenting with congenital tremor piglets

Closed herds

And new stock

In small closed herds it is possible for the resident animals to be or become naive.  Under these circumstances the introduction of  a new boar or other gilts will invoke the problem in piglets born to any pregnant sow.  In these circumstances the farm’s original sows and gilts have problems.

Sporadic cases

Congenital tremor is seen occasionally on most farms as an incidental occurrence and probably results from a gilt or possibly sow which has by chance remained naive until she became pregnant.

All other age groups

There are no clinical signs to born piglets, weaners, growers or adults who become infected for the first time.  The disease only affects the foetus.


The agent would appear to be very infective.  However, on modern farms disease transmission can be slow and it is possible for the disease to die out on a farm.  For this reason nucleus farms may produce naive gilts.

All materials are infective – faeces, placenta, nasal droplets, macerated piglets/foetuses and possibly semen


Pathogenesis (how the disease occurs)

A naive gilt or sow becomes infected while pregnant.  It would appear that getting infected at any time during gestation will result in the production of trembling piglets.   Once the female is immune / positive the second and subsequent litters will not demonstrate clinical signs.


There is no test for the virus.

Diagnosis is achieved by clinical signs alone.

Postmortem examination

There are no gross postmortem findings.  In cases of Swine Fever a reduction in the size of the cerebellum (part of the brain) may be noted (hypocerebellum).  In the other causes there are no clear postmortem changes that can be identified.

Treatment and Control

Piglet with trembles

There is no specific treatment.  The stockman can only provide help and assistance to the piglet with trembles.  For example:


Helping them to obtain colostrum, even by stomach tubing


Keeping the piglets warm


If necessary euthanase the piglets and using the gilt as a nurse sow


Do not breed from the infected piglets as it is possible they will produce trembling piglets themselves.



Adequate introduction programmes to the newly arrived gilt.  A minimum of 6 weeks between arrival and first service


Ensure the gilts are adequately ‘immunised’ to the farm’s diseases using faeces and if clinical problems are present placenta and macerated fetuses and dead piglets.  It is essential to ‘infect’ all naďve gilts before they become pregnant


In start up units /repopulation ensure that there is no evidence of the previous livestock. In particular all faecal material must be removed. Do not use old needles/syringes or medicine bottles.  Dispose of all old clothing.

Obtain “feedback” materials from the AI source – for example dead semen.


Do not cull unnecessarily the gilt/sow which had the trembling piglets as they should not produce affected piglets again


If there are any signs of Classical Swine Fever, immediately call your veterinarian


If hereditary congenital tremor is believed to be the cause avoid mating the sow and boar or siblings in subsequent matings

Zoonotic implications

There are no zoonotic implications