[Jacob-list] Ataxia: OCD, Lysosomal Storage Disease, etc.

[Jacobflock at aol.com]

I have noticed a few posts recently related to ataxia (loss of muscle 
control, more often noticed in the legs).  I would like to offer the 
following for your consideration; some of this being redundant (previous 
"list" responses and Journal articles) but perhaps timely inasmuch as many 
lambs are approaching that age when the symptoms are observed and diagnosis 
may be possible.

Occipital condylar dysplacia (OCD) symptoms can range from "no" ataxia to 
"severe" ataxia.  In the case of severe OCD there is a loss of muscle control 
(ataxcia) and the head may hang to one side with a "twist to the neck' or the 
head will hang down (toticollis).  The condyles (there are two at the base of 
the skull which should be equal in size and symetrical) which is where the 
first vertebrae in the neck joins the skull.  This is called the 
atlanto-occipital joint.  In some cases, the "hole" that the joint fits into 
... foramen magnum ... is not as large as it 'should' be.  The malformation 
of the condyles can cause a compression of the spine and the spinal cord.  In 
a sense, the spinal cord signals get shorted out by the compression caused by 
the bone malformation.  Being bone, it is rather easy to confirm by Xray or 
post mortem ... necropsy or butcher.

OCD is present in many species, in Jacobs it can be present in two and four 
horned, rams and ewes, and not every case is such that ataxia is observed.  I 
have looked at about 18 skulls since 1997 and have seen only one rather 
severe case (ataxic) and two 'mild cases (no symptoms but observed after 
butchering).  The symptoms for many cases of OCD seem to be observed first 
for lack of  "rear end" coordination (as opposed to front legs) and the 
pasterns for OCD cases seem to be properly aligned.  OCD is not lethal per se 
but OCD may lead to a higher incidence of death or severe injury from trauma 
resulting in severe spine compression.  OCD appears to have familial roots 
but its inheritance is not clear.  

Lysosomal storage disease (GM 1Gangliosidosis - accumulation of ganglioside 
in the cerebrum) presents similar symptoms, ataxia and recumbancy, but is a 
disease of the 'spinal cord' vs. spine. Lysosomal Storage Disease is a 
deficiency of the lysosomal enzymes that result in the storage of unprocessed 
waste material from the spinal cord process ... sort of like a sludge 
build-up because the Rid-X doesn't work.  In most of these cases, the 
symptoms begin with being slow and clumsy (often seen first as down on the 
front pastern and then ataxia in the rear end), the lamb lags behind, spends 
a lot of time lying around, and eventually dies. 

Lysosomal storage disease occurs in many species as well.  It also affects 
two and four horn, rams and ewes.   The presence and occurance of lysosoaml 
storage disease was found after presenting two live Jacob lambs as possible 
OCD cases.   In pursuing the cause for ataxia, it was found that the lambs 
had enlarged neurons with vacuoles and deficiencies of various hydrolases.  
This disease is an autosomal recessive and the Medelian genetics of this in 
Jacobs is approaching a conclusion.  The gene, chromosome, marker and test 
for the Jacob are still under study.

There are many other causes of ataxia.  This spring, a Jacob lamb was 
presented to a shepherd and the lamb had difficulty standing and an inability 
to raise its head to nurse.  It was bottle fed and shortly exhibited signs of 
convulsions .. eyes rolled bac, paddling on its side ... apparently severe 
ataxia and OCD?  The necropsy revealed the dorsal process of the second 
vertebrae broken and dettached.  Probably trauma at birth.  Trauma from lamb 
games or accidents can cause locomotion problems.  If a field has Swainsonine 
or Astragolus, ingestion can poison and cause symptoms like the lysosomal 
diseases.  Ataxia is also associated with scrapie ... white muscle ... 
polyarthritis ... and others.

The conservation of the breed depends on genetic health.  The $35 shovel is 
cheaper than the $75 necropsy but does not help the breed.  There are 
problems when trying to conserve a gene puddle.  Some of you may recall the 
list of about 50 congenital problems I made available to the associations 
last year.  We should continue to share information and thanks to the 
breeders who have.  

Fred Horak



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