Common Disorders affecting sheep Part 6 Neurological Diseases

Tetanus (Lockjaw)

  • limb stiffness, stilted gait
  • as disease advances, animal will stiffen completely and not be able to open jaw
  • convulsions, often triggered by sudden noises
  • 3rd eyelid membrane may be visible
  • breathing difficult
  • death occurs in 3-4 days

Cause/Transmission

  • bacteria in soil (Clostridium tetani) enters body through wound and produces a toxin which damages nervous system
  • bacteria grows in absence of oxygen, therefore deep puncture wounds are problematic
  • most often seen in lambs after castration or docking (elastrator bands and contaminated knives)

Treatment

  • usually too late by the time animal shows obvious signs
  • clean damaged area and any dead material
  • if animal has not been previously vaccinated, dose with tetanus antitoxin and tetanus toxoid (vaccine)

Prevention

  • vaccinate ewes using an 8-way (Clostridial and tetanus toxoid) prior to lambing
  • use clean equipment for castration and docking, house lambs in sanitary conditions
  • don’t use elastrator bands on farms with previous cases of tetanus

Listeria

Listeriosis (Circling Disease)
(also see abortion diseases)

  • most often seen in feedlot lambs, but also possible in animals of any age
  • depression, off feed, fever
  • one side of the body is affected (face paralysis, droopy ear, lip and eyelid)
  • animal walks in a circle
  • convulsions, death
  • diagnostic lab can identify bacteria and examine brain for abscesses

Cause/Transmission

  • bacteria (Listeria monocytogenes) forms abscesses in brain
  • contracted from infected sheep through cuts
  • spoiled feed (particularly silage) often implicated

Treatment

  • antibiotic treatment rarely successful

Prevention

  • provide good quality feed
  • properly dispose of deadstock
  • keep pregnant ewes away from sick lamb area

Polio Encephalomalacia

  • seen most often in feeder lambs
  • non-infectious (no fever)
  • may see blindness, staggering, head pressing, progressing to convulsions, coma, and death

Cause/Transmission

  • not known for certain, but thought to be a deficiency of thiamine (vitamin B1), due to microbes in the rumen depleting thiamine supplies (can be provided in diet but not available to the animal)
  • high mineral content in water may be a contributing factor
  • deficiency will eventually give rise to neurological disorder

Treatment

  • this is an emergency situation, (contact vet) but if the animal is treated quickly the prognosis is good
  • intravenous thiamine injections
  • separate animal during recovery

Prevention

  • consider adding brewer’s yeast to grain rations
  • avoid feeding mouldy hay
  • provide adequate water and water analysis

Ewe with scrapie

Scrapie

  • relatively rare, but reportable disease
  • long incubation time, animal may be infected at birth but no signs until sheep is 2yrs or older
  • typically extensive loss of wool due to rubbing
  • uncoordinated, muscle temour, twitching, grinding teeth, convulsions
  • some sheep die quickly with few signs, most die within six months of first signs
  • diagnosis only confirmed by lab exam of the brain after death

Cause/Transmission

  • prion disease (abnormal protein in body which builds up in nervous tissue)
  • transmitted to lambs and older sheep that come in contact with placenta and birth fluids of an infected animal

Treatment

  • no treatment
  • reportable by law, contact your vet immediately if you suspect your flock may be infected

Prevention

  • careful screening of breeding stock sources
  • voluntary federal scrapie program is in development to identify flocks at risk of infection, may involve liveanimal test and/or testing for genetically resistant animals

Rabies

  • restlessness, twitching lips, excessive drooling (note: not all drooling animals will have rabies, often may be an obstruction in the throat or mouth, however, always wear gloves if you may come in contact with salvia)
  • animals may act either excessively docile (depressed form) or aggressive butting against wall or fence etc.
  • males may show sexual behaviour
  • animal is progressively paralyzed and generally dies within six days

Cause/Transmission

  • viral disease which attacks the central nervous system
  • usually contracted from the bite of an infected animal (dog, fox, skunk etc.)

Treatment

  • none
  • reportable disease, contact your veterinarian immediately

Prevention

  • no vaccine for sheep
  • vaccinate farm dogs annually
  • control populations of potential carriers (foxes, skunks etc.)