Published Date: 2001-10-29 23:50:00
Subject: PRO/AH> Chronic wasting disease, cervids - USA (Colorado) (04)
Archive Number: 20011029.2670

CHRONIC WASTING DISEASE, CERVIDS - USA (COLORADO) (04)
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See Also

Chronic wasting disease, cervids - USA (Colorado) 20010217.0314
Chronic wasting disease, cervids - USA (Colorado) (02) 20010924.2317
Chronic wasting disease, cervids - USA (Colorado) (03) 20011025.2635
Date: 26 Oct 2001
From: Conor Kretsch <Conor.Kretsch@enviros.com> [edited

Some questions on CWD:
------------------------------
Q. CWD is the elk and deer equivalent of 'mad cow disease' (BSE),
thought to be caused by a similar prion infective agent. Previous
postings to ProMED-mail have expressed concerns that CWD can be
transmitted from livestock to wild populations. Considering that the
source and spread of BSE among livestock is thought to be related to
the feeding of offal to those animals, why then is it thought that CWD
can be transmitted otherwise? Has it been determined that it can be
transmitted laterally/passively from one individual to the next?
A. [There is some evidence BSE can be transmitted to the offspring,
while in utero. Likewise, perhaps, from consumption on the grass, after
it has passed through the animal. Based upon the BSE experience, it is
believed to be the same with CWD. - Mod.TG
Q. If not, why then are whole herds of livestock being wiped out in a
reaction similar to the cull of animals in Europe following the FMD
epidemic this summer?
A. [Please see the answer to the question above. - Mod.TG
Q. How different is it then from other TSEs?
A. [There are a number of subtle differences between the different
TSE's. The appearance of the lesions, the location of the codons, and
probably many other unknowns because there is not a lot of research in
CWD. - Mod.TG
Q. Bearing in mind that CWD has been detected in wild deer and elk
for over 30 years, and if it can be transmitted passively, it is possible
that an outbreak in domestic animals could have arisen from contact
with wild animals -- wouldn't fears of transmission to wildlife then be
over-reactive? i.e., it would not be outside the normal ecological cycle.
A. [A good question for which there is no answer, presently. - Mod.TG
Q. If the origin of CWD is in the wild populations, and at least 30 years
old, one could infer that this origin has been 'natural,' i.e., not caused
by forced feeding of offal. Theories that it arose from wild animals
who chewed bones of dead animals to obtain mineral supplement
would seem illogical, assuming that this behaviour is probably as old as
the species themselves and CWD has apparently not caused an
ecological disturbance before (and does not do so now?). Therefore,
epidemiology of transmission notwithstanding, couldn't BSE and other
TSEs also have originated naturally?
A. [This has always been a speculation, yet remains to be proven. -
Mod.TG
­­
Conor E. Kretsch
Consultant Scientist
Enviros ltd.
<Conor.Kretsch@enviros.com>
.................................tg/pg/jw
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