From: TSS (216-119-132-111.ipset12.wt.net)
Subject: NECROPHAGOUS BIRDS AS POSSIBLE TRANSMITTERS OF TSE/BSE
Date: January 14, 2005 at 1:03 pm PST
NECROPHAGOUS BIRDS AS POSSIBLE TRANSMITTERS OF TSE/BSE
THE SCIENTIFIC STEERING COMMITTEE
AT ITS MEETING OF 7-8 NOVEMBER 2002
BACKGROUND AND MANDATE
Concern has been raised to the theoretical risk that carrion1 or necrophagous birds could play a
role in the spread of TSE and exposure to TSE of humans by contracting the disease, by
spreading the agent passively in waste from their food or by exposure of persons involved in
handling the birds and the direct release of the agent in the environment. On 9 October 2001
the CMIEET (Multidisciplinary Scientific Committee for Research into Transmissible
Spongiform Encephalopathies, Spain), adopted a scientific opinion and report on Carrion birds
as possible vectors of bovine spongiform encephalopathy and on possible alternatives to the use
of ruminant carcasses as food for these animals. The Scientific Steering Committee was
subsequently requested to:
(1) Evaluate the opinion of the Spanish Scientific Committee on TSEs in relation to
necrophagous birds being possible transmitters of BSE and
(2) Advise on the safety with regard to TSE risks for the use of dead ruminants containing
specified risk material (SRM) for the feeding of necrophagous birds and, if appropriate,
suggest examples of conditions under which such feeding can be carried out safely.
The opinion hereafter pays special attention to the above mentioned spanish report and is based
on the discussions held by the TSE/BSE ad hoc Group at its meetings of 25 July and 5
September 2002 (rapporetur: Dr.E.Vanopdenbosch), as well as contributions from
Prof.Dr.L.Bolis, Dr.P.Brown and Dr.R.Bradley.
1. Necrophagous birds as possible transmitters of BSE.
The SSC considers that the evaluation of necrophagous birds as possible transmitters of
BSE, should theoretically be approached from a broader perspective of mammals and
birds which prey on, or are carrion eaters (scavengers) of mammalian species. Thus,
carnivorous and omnivorous mammals, birds of prey (vultures, falcons, eagles, hawks
etc.), carrion eating birds (crows, magpies etc.) in general could be considered possible
vectors of transmission and/or spread of TSE infectivity in the environment. In view also
of the occurrence of Chronic Wasting Disease (CWD) in various deer species it should not
be accepted that domestic cattle and sheep are necessarily the only source of TSE agent
exposure for carnivorous species. While some information is available on the susceptibility
of wild/exotic/zoo animals to natural or experimental infection with certain TSE agents,
nothing is known of the possibility of occurrence of TSE in wild animal populations, other
than among the species of deer affected by CWD in the USA.
1 The carrion birds are animals whose diet regularly or occasionally includes the consumption of carcasses,
including possibly TSE infected ruminant carcasses.
The SSC therefore took, in addition to the opinion of the Spanish CMIEET, also the
following publications into account2:
- SSC Opinion (1999) on the risks of non conventional transmissible agents,
conventional infectious agents or other hazards such as toxic substances entering the
human food or animal feed chains via raw material from fallen stock and dead animals
(including also: ruminants, pigs, poultry, fish, wild/exotic/zoo animals, fur animals,
cats, laboratory animals and fish) or via condemned materials.
- SSC Opinion (1999) on the risk born by recycling animal by-products as feed with
regard to propagating TSE in non-ruminant farmed animals.
- SSC Opinion (2000) on the Scientific basis for import bans proposed by 3 member
states with regard to BSE risks in France and the Republic of Ireland; on the Scientific
basis for several measures proposed by France with regard to BSE risks and on the
Scientific basis for banning animal protein from feed for all farmed animals, including
pig, poultry, fish and pet animals.
- Scrimgeour, E. M., et al., 1996. Disposal of rendered offal. The Veterinary Record,
August 31, 219-220. This paper raises the issue of birds as uninfected vectors of
infectivity from landfill carcass sites in 1996.
- Tella, J.L., 2001. Action is needed now, or BSE crisis could wipe out endangered
birds of prey. Nature, 410: 408.
The SSC analysed the above literature from the following perspectives:
- The risk of TSE infection and agent replication in birds in general and in necrophagous
birds in particular;
- Risk of passive spread of TSE
- Human exposure risk
It concluded as follows:
- The scientific basis (both literature and field data) for advising on the safety with
regard to TSE risks, of the use of dead ruminants containing specified risk material
(SRM) as bird feed, is very limited. As far as birds are concerned, most data relate to
the domestic fowl. No literature could be found on aspects such as microscopic brain
examinations in zoo carnivorous/omnivorous birds (often fed on waste bovine material
that in the past may have been infected with BSE) nor on the epidemiology of TSEs as
possibly influenced by the role of prey animals and carrion eaters (scavengers)3.
2 The opinion of 9 October 2001 of the CMIEET was originally prepared in Spanish and a translation of the
opinion into English is therefore attached to this opinion for ease of reference. At certain places, comments made
by the TSE/BSE ad hoc Group at its meeting of 25 July 2002 have been introduced and they are highlighted.
3 It would hardly be possible to analyse this possible role with an epidemiological design.
- The possibility of active replication of PrPSc in birds is remote, if existing at all.
(Necrophagous and omnivorous) birds are nevertheless able to ingest BSE infectious
material and to spread the ingested infectious material through dissemination of faeces
because it is unlikely that the pathological prion protein would be completely
destroyed in the digestive tract. Moreover, plumage, claws and beak may also be
contaminated with infectious material, which is then released into the environment.
- Although there is no data on TSE epidemiology indicating any significant role of any
such pathways in the spread of scrapie, it cannot be excluded that they could play a
part in the transportation of TSE infected materials, given that these birds can cover
great distances and may also migrate.
2 safety with regard to TSE risks of the use of dead ruminants containing specified risk
material (SRM) for the feeding of necrophagous birds; examples of conditions under
which such feeding can be carried out safely.
One could theoretically consider implementing rigorous health measures to prevent birds
from having access to carcasses of animal species susceptible to TSE, but in view of the
very limited human exposure risk this may bring about changes to the ecology created by
the traditional practices and could jeopardise the conservation of certain animal species.
On the other hand, feeding practices should not lead to an artificial increase of the number
of potential TSE transmission sources, and their possible spread. Whereas it is recognised
that the removal of fallen animals from remote wild areas is not a realistic option under all
circumstances, the SSC considers that feeding programmes of wild species such as
necrophagous birds should thus not become an alternative way of disposal of fallen
ruminant stock posing a TSE risk nor of specified risk materials.
The SSC considers that the above recommendations are for the time being also valid for
other prey animals and carrion eaters (scavengers), for which even less literature is
3. The above conclusions are consistent with the opinion of 9 October 2001 of the CMIEET and with
its main conclusions.
I. EXECUTIVE SUMMARY
The eradication of TSEs will require the removal of potential sources of the agent, such as
bovine (and ovine) carcasses, from the natural environment. This will result in the elimination, or
at least the reduction, of food sources for necrophagous species, for the conservation of which
Spain has responsibilities unique in Europe.
There are no studies on the presence of TSE in necrophagous birds, nor is there any solid
evidence that such processes affect birds in general. In fact, it has not even been possible to
demonstrate birds’ sensitivity to BSE under test conditions. This absence of observations can
theoretically be explained by the low level of similarity — only 30% — between prion protein
sequences of birds and mammals.
The possibility of necrophagous birds’ digestive systems being somehow adapted to breaking
down and extracting nutrients from prion proteins could be of great importance, not only in the
interests of ensuring environmental biosafety but also as a potential final stage in the elimination
of TSE risks: there is therefore a case for research into this issue.
There are two alternatives to deal with the immediate problem of food for necrophagous birds: a)
keep using bovine carcasses, but on the condition that rapid test results are negative b) replacing
them by other species not susceptible to BSE. The first alternative will not result in any
substantial increase in costs since tests on all dead bovines have been obligatory since 1 July
2001 (Order of 26 July 2001). The second could create complex logistical problems and be
considerably more expensive in regions where numbers of such species are low.
Consideration should be given to a moratorium on the use of sheep carcasses until it can be
demonstrated that any cases of scrapie emerging in this country are unrelated to processes caused
by the BSE agent.
If we take the global view of the issue of prions in the environment, we should also pay special
attention to the possible problems related to other wild species documented as being susceptible
to TSEs, such as mustelids (occasional carrion eaters) and cervids. We must also not lose sight of
the potential for disaster if the Iberian lynx, a unique and endangered species, were to become
involved in a possible wild BSE cycle.
We must also draw attention to the need for detailed studies of costs and of the uncertainties
surrounding the numbers of domestic species and carrion animals, and for research into their
susceptibility to TSEs and into the role which other wild species may play in the survival and
spread of TSEs in the natural environment.
II. SUBJECT MATTER
Carrion birds as possible vectors of bovine spongiform encephalopathy. Possible alternatives to
the use of ruminant carcasses as food for such animals
III. DEFINITIONS AND ABBREVIATIONS
Carrion or necrophagous animals: Carnivorous or omnivorous animals whose diet regularly or
occasionally includes the consumption of carcasses. Annex I contains a list of the specific
carrion birds referred to in this report.
AC: Autonomous Community
TSE: Transmissible spongiform encephalopathy
BSE: bovine spongiform encephalopathy
SRM: specific risk materials
PrP: Prion protein
PrPC: normal prion cellular protein
PrPSC: Resistant or pathological prion protein associated with scrapie and considered to be
responsible for transmissible spongiform encephalopathies
SEO: Sociedad Española de Ornitología (Spanish Ornithological Society)
CNS: Central Nervous System
snip...FULL TEXT 21 PAGES ;
German ostriches may have mad cow disease
Ostriches are showing BSE-type symptoms in Germany.
The birds have fallen ill after being fed animal bonemeal, which is blamed for causing the disease in cows.
German newspaper Die Zeit reports that the symptoms have been seen in ostriches in various zoos.
The paper says Britain's Ministry of Agriculture has ordered research to be conducted into the possible transmission of BSE from cattle to birds.
Vets at a Hanover college who examined the brains of the affected animals reported that they found the same kind of holes in the ostrich brains as were found in BSE-infected cattle.
Other experts have dismissed any transmission of BSE to birds. No BSE cases have been reported from commercial ostrich farms - because their animals are slaughtered before they are old enough to develop the illness.
A CONTRIBUTION TO THE NEUROPATHOLOGY OF THE RED-NECKED OSTRICH (STRUTHIO CAMELUS) - SPONGIFORM ENCEPHALOPATHY
Any risk with dumping deer?
especially the possibility of dumping more than 2 million pounds of deer carcasses in a county landfill.
"I have two goals," Falk said, "to protect public health and to protect our deer herd."
"Do we need to worry about the carcasses leaking through the membrane of the landfill?" Falk asked. "Or our groundwater becoming contaminated?"
Brett Hulsey, one of the County Board supervisors who will introduce the task force resolution, said dealing with the disease will require some tough choices - chief among them deciding whether to allow the disposal of possibly diseased deer in the Dane County Landfill.
Gary Johnson, public health manager for Dane County, said the problem is that prions are very hard to destroy and have been shown to linger for years. He said England's experience with mad cow disease, a similar prion disease that did pass to humans and killed more than 100 people, should be an example. Just as with CWD here in the states, Johnson said, people were told mad cow disease wasn't a human health threat.
indent"People were saying the same thing," Johnson said, "and taking more comfort from that than they should have. We don't want to be too confident about this given that what we don't know may come back to hurt us later."