Congenital Tremor
Agent |
A variety of events, diseases,
toxins etc can cause a piglet to present with congenital tremor |
|
1 |
The
most common cause is an unidentified viral agent |
|
2 |
There
are a number of genetic causes – Landrace trembles, Saddleback tremors |
|
3 |
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
|
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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. |
|
Infectivity
|
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. |
|
Diagnosis
|
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: |
|
1 |
Helping
them to obtain colostrum, even by stomach tubing |
|
2 |
Keeping
the piglets warm |
|
3 |
If
necessary euthanase the piglets and using the gilt
as a nurse sow |
|
4 |
Do not
breed from the infected piglets as it is possible they will produce trembling
piglets themselves. |
|
Control |
||
1 |
Adequate
introduction programmes to the newly arrived
gilt. A minimum of 6 weeks between
arrival and first service |
|
2 |
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 |
|
3 |
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. |
|
4 |
Do not
cull unnecessarily the gilt/sow which had the trembling piglets as they
should not produce affected piglets again |
|
5 |
If
there are any signs of Classical Swine Fever, immediately call your
veterinarian |
|
6 |
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 |