2. Diseases of the central nervous system

1. Cerebral Diseases

a. Hydrocephalus
etiology usually unknown
some lambs with Border disease have domed skull (hairy shakers)

b. Other Congenital Defects
impossible to tell if genetic, infectious, environmental or chance if only one case

c. Veratrum californicum Poisoning
wild lily in mountains of western USA
steroidal alkaloids such as cyclopamine induce cyclopia and cebocephalic defects on day 14
pituitary lesion may prevent normal delivery - lambs grow very large in utero

d. In utero Viral Infections
Bovine virus diarrhea/Border disease, Bluetongue, Akabane and Cache Valley bunyaviruses,
Rift Valley Fever, Wesselsbron Disease (Africa)
arthrogryposis often causes dystocia

e. Congenital Toxoplasmosis
Toxoplasma gondii
cat is definitive host, kittens shed infective oocysts - hay, grain, or pasture contaminated
white necrotic/mineralized foci in cotyledons, mummified or stillborn fetuses
some lambs and kids weak and die soon after birth
lymphoid perivascular cuffs and glial cell foci

f. Beta Mannosidosis
inherited, autosomal recessive defect of AngloNubian goats
lysosomal storage disease, recognizable at birth
deficiency of beta mannosidase causes vacuolation and destruction of cells in all tissues
kids unable to rise at birth, carpal flexion, domed skull, small palpebral fissures
pendular nystagmus, intention tremors, soon die

g. Polioencephalomalacia, Cerebrocortical Necrosis
noninfectious laminar necrosis of the cerebral cortex
brain fluoresces under ultraviolet light
thiamine deficiency (including disturbances of rumen function), sulfur toxicity
blindness, circling, nystagmus, dorsomedial strabismus, opisthotonos
treat with thiamine - 10 mg/kg t.i.d.
increase roughage, decrease sulfates in diet
lead poisoning is extremely rare as cause of neurologic signs in small ruminants

h. Pregnancy Toxemia
Pregnancy with multiple fetuses can lead to ketoacidosis if inadequate energy consumed (poor feed,
storm, other illness, too fat initially)
Grain overload will often precipitate pregnancy toxemia by putting animal off feed
may have simultaneous cerebrocortical necrosis
depressed, separates from flock, poor vision
check for ketones in urine (hold off nose)
see later lecture for treatment

i. Meningitis
young lambs and kids with navel infection
herd outbreaks with streptococcal infections in adults
purulent meningitis visible grossly as cloudy meninges

j. Dehorning Injury
proper age to disbud European breed goat is 3 (male) to 7 (female) days
no protective sinus at this age
too long an application of too cold a dehorning iron damages bone or cerebrum

k. Oestrus ovis
occasionally penetrates cribriform plate between sinus and brain
hemorrhagic nasal discharge, cerebral signs
too late for ivermectin!

l. Gid, Coenurosis
Coenurus cerebralis, intermediate stage of tapeworm Taenia (Multiceps) multiceps of dogs
stargazing, depressed, blind, wander aimlessly, ataxia, convulsions, death - acute
ataxia, blind, high-stepping gait, circling, softening of overlying bone - chronic
prevent by treating farm dogs for tapeworms, do not allow access to sheep carcasses

m. Rabies
zoonotic virus
infected by bite of fox, dog, raccoon, skunk, vampire bat
signs variable - quiet or aggressive, may ride other animals (sexual behavior)
death within 8 days

2. Cerebellar and Brainstem Diseases

a. Polioencephalomalacia with coning of the cerebellum
Swelling of brain forces part of cerebellum through foramen magnum
terminal stage - mannitol might decrease swelling

b. Enterotoxemia/Focal Symmetrical Encephalomalacia
epsilon toxin produced by Clostridium perfringens type D
often sudden death in rapidly growing animals
hyperesthesia, ataxia, recumbency, opisthotonos, nystagmus, convulsions, diarrhea
histology of brain shows perivascular edema, vascular hemorrhage, focal malacia
symmetrical reddened foci in corpus striatum, thalamus, midbrain, cerebellar peduncles if live longer
all sheep and goats should be vaccinated against enterotoxemia C and D
antitoxin useful for prophylaxis; treatment rarely successful

c. Listeriosis
Listeria monocytogenes - various serotypes, but especially 4b
 cold enrichment - multiplies in refrigerator and in spoiled silage in winter  (pH>5)
zoonotic; reportable (meldepflichtig) in Germany but not in USA
meningoencephalitis when organism travels up trigeminal nerve from mouth or conjunctiva
"circling disease", ataxia, leans against wall
facial nerve paralysis - drooping ear or lip, unable to blink - often unilateral
 exposure keratitis or traumatic injury (do not confuse with infectious keratoconjunctivitis)
drooling, weak jaw or tongue
microabscesses in brainstem, mononuclear cells in CSF
antibiotic treatment often disappointing; tetracycline if start early
(abortions, septicemia, microabscesses in liver of lambs)
avoid spoiled silage, dirt in silage
commonly secreted in milk and feces of silage fed animals

d. Caprine Arthritis-Encephalitis Virus
retrovirus infection discussed in detail under spinal cord diseases and CAE portion of infectious disease
lecture of 3.7.00
if lesions in brainstem, clinical signs can mimic listeriosis
kids with CAE usually younger than those with listeriosis, but not invariably; adults sometimes show
neurologic signs

e. Scrapie
prion disease, agent is very resistant to chemicals and time
a transmissible spongiform encephalopathy, but not same as bovine spongiform encephalopathy
agent apparently shed at time of parturition, goats infected if mixed with sheep
breed differences in susceptibility/incubation period
Suffolk breed in the USA - there is a DNA test for resistance
Cheviots, Swaledales, in UK
new third eyelid test for diagnosis in live animals does not work for older animals with no lymphoid  tissue in the third eyelid!
clinical signs typically at 2 to 5 years of age
signs include pruritus, hyperexcitability and trembling, ataxia, weight loss, sudden death
vacuolation in brain stem without inflammation, scrapie associated fibrils (SAF) on electromicroscopy

3. Spinal Cord Diseases

a. Caprine Arthritis-Encephalitis Virus, CAE
lentiviruses - sheep and goat viruses are distinct but serologically similar
reverse transcriptase, animal remains infected for life
5 main clinical manifestations:
 interstitial pneumonia
 interstitial mastitis

neurological form most common in 2-6 month old kids, can affect adults
posterior paresis most common but can involve any part of brain or spinal cord
lesions are grossly visible - pinkish gray, asymmetrical
cerebrospinal fluid helpful - obtain from atlanto-occipital or lumbosacral space
normal in goats < 40 mg/dl protein, < 5 cells/cmm

b. Maedi-Visna
visna form may show behavior changes, circling, ataxia, posterior paresis

c. Tail Docking Infections
ascending bacterial infections

d. Copper Deficiency, Swayback, Enzootic Ataxia
inadequate copper or excess molybdenum
congenital form: uncoordinated from birth, head tremor, nystagmus, opisthotonos, unable to suckle,
 may be stillborn
cerebral white matter degeneration, chromatolysis of neurons in red and vestibular nuclei
delayed swayback appears when several weeks or months old; hind limbs sway, spinal cord
demyelination, chromatolysis of neurons in ventral horns - irreversible
non-neurologic signs include loss of wool crimp, depigmentation, anemia, illthrift, diarrhea,
osteoporosis, low fertility
diagnose from histology, low liver copper (< 10 mg/kg) or low plasma (serum, blood) copper
supplement copper by injection, copper wires orally, supplementation of salt, fertilizer, etc
avoid copper toxicity!

e. Cerebrospinal Nematodiasis
parasitic migration through spinal cord
Parelaphostrongylus tenuis carried by white-tailed deer (Odocoyleus virginianus) in eastern North America
 snail or slug is intermediate host
Elaphostrongylus rangiferi carried by reindeer in Scandinavia
Setaria digitata in cattle in Asia - spread by mosquitoes
eosinophils in CSF

4. Peripheral Diseases

a. Tetanus
toxin produced by anaerobe Clostridium tetani binds to neurons
all muscles stiff, extensors stronger, difficult to open jaw
bloat, constipation
no lesions at necropsy
all sheep and goats should be vaccinated unless slaughtered before colostral immunity wanes
tetanus antitoxin (250 to 500 IU) provides temporary protection if wound or surgery
treat valuable animal with penicillin, antitoxin, force feeding (fistula)

b. Botulism
preformed neurotoxin produced by Clostridium botulinum
dead animals in feed or water
voice change, depression, difficulty chewing, salivation, tremble, unable to stand, death
differential includes hypocalcemia, tick paralysis

5. Floppy Kid Disease
cause unknown, though behaves like toxin (botulism, but recovers too fast)
acute weakness in kids 3-10 days old
no previous diarrhea
metabolic acidosis without dehydration, increased ion not identified
depressed, weak, down, unable to suckle, abdominal distension
low temperature or fever
24-36 hour course
up to 100% of kids affected - all breeds
normal at birth, received colostrum, raised on dam or artificially
treat with 125 - 200 ml of 1.3% sodium bicarbonate IV or 2.5 g sodium bicarbonate orally
take off milk 24 hours
often disappears from herd next year

(6. Heartwater)
tickborne rickettsia, Cowdria ruminantium
southern Africa, Caribbean
fever, neurological signs: bleating, hyperesthesia, muscle twitching, nystagmus, circling, terminal
cerebral edema, fluid in body cavities
tetracycline to treat

Behrens, H.: Lehrbuch der Schafkrankheiten
Smith, M.C.: Goat Medicine
Linklater, K., Smith, M.C.: Color Atlas of Diseases and Disorders of the Sheep and Goat
Martin, W.B.: Diseases of Sheep
Zettl, K., Brömel, J.: Handbuch Schafkrankheiten

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