Diseases of the nervous system

Question 1

Congenital neurological diseases

Answer 1

Meningoencephalocoele

Congenital tremors

Question 2

Bacterial neurological disease

Answer 2

Streptococcal disease

Abscessation

Tetanus

Botulism

Question 3

Viral neurological diseases

Answer 3

Aujeszky’s Disease*

EMCV

Vomiting + Wasting Dis.

Teschen*

CSF*

Rabies*

Louping Ill

Question 4

Physical factors causing neurological disease

Answer 4

Pathological fracture

Injuries

Question 5

Nutritional causes of neurological disease

Answer 5

Neonatal hypoglycaemia

Water deprivation

Deficiency (Vit. A, B)

Toxicity (Se,mycotoxin)

Question 6

Congenital meningoencephalocoele

Answer 6

A rare autosomal recessive defect in which the cranium is not fully closed at the time of birth.

Meninges and occasionally cerebral hemispheres protrude between the cranial bones.

Reported in Large White and Landrace pigs.

Euthanasia in affected piglets.

Eliminate by avoiding repeated breeding of affected litter parents and identifying and culling carrier animals.

Question 7

Congenital tremor

Answer 7

A group of at least six diseases affecting neonatal piglets.

hypomyelinogenesis and muscular tremor.

increased sensitivity of their spinal cord reflexes

made worse by developing hypoglycaemia.

may appear normal at birth with signs of tremor developing when they are 3 days old.

One form of the disease (A1) is caused by the Classical Swine Fever Virus and this must be eliminated from the diagnosis of tremor in every case.

Consequences of all are:
* Hypomyelinogenesis
* Cerebellar hypoplasia

Question 8

Congenital tremor type A 1

Answer 8

CSF virus affects sows at 10 - 50 days gestation. Approx. 40% of litter is affected.

male and female piglets equally affected.

Several litters of any breed affected.

High mortality in affected piglets.

Tremor, ataxia, and collapse.

Notifiable

Question 9

Congenital tremor type A 2

Answer 9

probably viral. Enteroviruses have been implicated and more recently atypical porcine pestivirus (APPV).

male and female piglets equally affected.

Several litters affected over a period of several months.

High % piglets affected in litters but most survive and improve if they are able to suck colostrum/feed.

Subsequent litters from same parents not affected.

Question 10

Congenital tremor type A3

Answer 10

Hereditary, sex-linked

Male Landrace

Question 11

Congenital tremor type A4

Answer 11

Hereditary, not sex-linked

British Saddleback

Question 12

Congenital tremor type A5

Answer 12

Toxic, organophosphate

Frequency declined in parallel with OP use

Question 13

Congenital tremor type B

Answer 13

Unknown

Seen in a lot of breeds

Question 14

Hypoglycaemia in neonatal pigs

Answer 14

very common and a major cause of piglet mortality.

low blood sugar usually the result of inadequate milk

Hypothermia exacerbates the problem

The risk is greatest in the first 3 days of life. Mortality if untreated can be 100%

Enteritis, which is very common at this stage of life, reduces the efficiency of glucose absorption from the gut.

general weakness, incoordination, walking with a wide - stance hind limb gait. Low temperature, shivering, pallor and hairs of coat standing on end. Weak, reedy squeal. Terminal recumbency, convulsions and death. May also see galloping/paddling movements, champing of the jaws and opisthotonus.

blood glucose of < 2.8
mmol / L

Treatment - 15 ml of 20 % glucose solution given intra-peritoneal

Question 15

Water deprivation -salt poisoning

Answer 15

either excessive salt in diet or rapid rehydration following water deprivation.

condition is caused by a lack of water for 12 hours or more, then pigs drink excessively to quench their thirst

Toxic dose of salt for pigs is 2.2g / Kg body weight

In water deprivation cases sodium ions build up in the extracellular fluid in the brain

very large doses of salt may cause severe gastro-enteritis but CNS signs predominate in cases of water deprivation

pruritis and head pressing. Periodic convulsions occur at intervals of several minutes. The pig adopts a dog sitting position or lies in sternal recumbency. Nodding and champing

Post mortem - eosinophilic meningitis and possibly gastro-enteritis.

Treatment - slow rehydration with small aliquots of water. Mannitol at 2g / kg and 20 min later Dexamethasone at 1mg / kg both i/v. CSF withdrawal by lumbar puncture may also help

Question 16

Streptococcus suis meningitis and septicaemia (pre-weaning – usually serotype 1)

Answer 16

common and important disease of preweaning piglets.

Most commonly Streptococcus suis Type 1

enters piglet’s body through the tonsillar crypts, umbilicus or skin lesion

becomes systemic in susceptible animals causing a septicaemia

Abrasive environments exacerbate clinical disease

Mostly affects piglets aged 10 - 14 days.

dull, pyrexic T 40 - 41 and up to 66% of the litter may show some signs of infection

Joint involvement, meningitis, endocarditis

Treatment - immediate treatment with parenteral antibiotic - penicillin, ampicillin or trimethoprim sulpha. May also use steroids or NSAIDs to reduce inflammatory changes

Autogenous vaccination successful when correct strain(s) is identified from pathology and vaccine administered to sows before farrowing.

Question 17

Streptococcus suis serotype 2 & Type 14 infection (postweaning)

Answer 17

Can also affect people by zoonotic spread

often occurs 3 - 7 days after environmental stress

protected until passive immunity wanes – enabling them to develop acquired immunity

bug settles in tonsillar crypts.

Strep suis Type 2 has a polysaccharide capsule which protects it from phagocytosis and allows it to spread rapidly through the body

seen in weaners, growers and finishers

first sign in a group may be a sudden death.
anorexic and pyrexic T 40 - 41 C. acute arthritis with warm, swollen and painful joints.
meningitis – with recumbency, convulsions and nystagmus. Redness of skin and fever. Pleuropneumonia with dyspnoea.

Treatment - aggressive antibiotic therapy - penicillin, ampicillin, trimethoprim sulpha etc. NSAIDs may also help.

S. suis serotype 2 bacterin is available in some countries (not UK) but this has limited efficacy. Autogenous vaccines have moderate efficacy and best results achieved when applied to sows pre-farrowing rather than to piglets – though protection lasts only as long as passive antibody from sow (c. 4-5 weeks age). May also be given to piglets, but best after weaning, because colostral antibodies interfere with vaccine effectiveness.

Question 18

Abscesses in pigs

Answer 18

Trueperella pyogenes, Str. suis, Staph. aureus, F. necrophorum,

from fighting, tooth clipping, tail docking / biting, castration, mastitis, vaginal injury.

Tail bite infections track up lymphatics along vertebral column with pathological fractures or pressure on spinal nerves / sciatic nerve may cause caudal ataxia and weakness.

Outer ear infections track to middle ear affecting balance.

Tail bite sequelae - hind limb ataxia and weakness.
Middle ear infection: head tilt, nystagmus

Rule out other infectious causes.

Consider welfare and cull as appropriate. Attempt long term antibiotic and anti-inflammatory treatment if appropriate

Question 19

Aujeszky’s Disease (AD) (Pseudorabies (PRV))

Answer 19

Eradicated from UK (NOTIFIABLE)

Swine herpesvirus 1 – an alphaherpesvirus

non-suppurative meningoencephalitis, necrotic bronchitis and alveolitis

May enter herd through carrier animals infected for life (latent in trigeminal ganglia)

Pathology includes cerebral oedema / haemorrhage; necrotic white foci in liver, spleen, tonsil.

Histology - inclusion bodies in peripheral nerve ganglia cells and signs of a viral encephalomyelitis.

Treatment - none really effective. Poor prognosis for young piglets. Possible recovery in adults - but become carriers. Slaughter policy

Question 20

Aujeszky’s Disease (AD) (Pseudorabies (PRV)) in piglets

Answer 20

short incubation period (2-4d) may initially see vomiting and diarrhoea, T 41 C.

Respiratory signs and ill thrift.

CNS signs develop - incoordination, convulsions, recumbency and death.

May see cold sore-like lesions on mouth, snout and face.

Mortality <100% in naïve herds.

Question 21

Aujeszky’s Disease (AD) (Pseudorabies (PRV)) in weaned pigs

Answer 21

anorexia and then respiratory signs may predominate.

T 41 C.

Respiratory signs.

CNS signs may not be seen in this age group.

But some show incoordination and hind limb paresis.

Question 22

Aujeszky’s Disease (AD) (Pseudorabies (PRV)) in grower-finishers

Answer 22

respiratory signs (cough, dyspnoea, nasal discharge).

6-9 day duration.

Exacerbated by other respiratory pathogens.

CNS signs (muscle tremors to convulsions)

Question 23

Aujeszky’s Disease (AD) (Pseudorabies (PRV)) in sows and gilts

Answer 23

may have reproductive failure with abortion, early embryonic death and a vaginal discharge.

Respiratory signs, and occasional CNS signs.