I don't think raw egg whites affect thiamin, but...
 
Quoting Bob Church's Nutrition files (he's a source I'd trust):
"Vitamin H, biotin, helps in the maintainence and growth of skin and hair,
and of the nervous system.  Deficiency symptoms include dermatitis, fur
loss, and nervous system disorders.  Raw egg whites inactivate the
vitamin.  Little body storage."
 
From other discusions, Church elaborates to say that raw egg whites bind
the biotin, making it unavailable to be metabolized.
 
"Vitamin B-1, thiamin, helps to metabolise energy-producing compounds.
Deficiency symptoms are impaired metabolism of carbohydrates, and can
result in a disease called Beriberi.  Little body storage....Sulphur (S)
is essential for the formation of amino acids, tissue respiration, and in
the formation of Biotin and Thiamine.  Deficiency symptoms include poor or
stunted growth."
 
From what I understand, it's a long term use of raw egg whites that is to
be avoided, an occasional use is not of consequence However, cooked egg
whites do NOT bind the biotin.  Egg whites or whole eggs in commercial
foods have been processed or cooked so that they do not affect biotin.
 
I frequently add egg yolk to soups for insulinoma ferrets that need an
assured and highly condensed source of animal protein (because they won't
eat much at a time.) And I use raw egg yolk as an emergency protein source
following honey to stop an insulinoma induced episode or seizure.
 
(NOTE: For ferrets with concurrent renal/kidney problems, high protein
content foods are usually NOT recommended; consistent and frequent lower
protein foods must be given instead.)
 
Debi Christy
Ferrets First Foster Home
 
Practical & easy training, care, & maintenance articles available at
http://www.geocities.com/ferretsfirst/
[Posted in FML issue 3616]