The ethics of research involving animals - Nuffield Council on ...

T h e e t h i c s o f r e s e a r c h i n v o l v i n g a n i m a l s
6.22 <strong>The</strong> results from these and many similar studies on the pathogenesis and transmission <strong>of</strong> TSE
between <strong>animals</strong> have been used to develop policies for public health to prevent the
transmission <strong>of</strong> BSE from cattle through the human food chain. Specifically, they led to the
banning <strong>of</strong> bovine <strong>of</strong>fal for human consumption, the removal <strong>of</strong> brain, spinal cord and
dorsal root ganglia, and the deboning <strong>of</strong> beef intended for public consumption. Based on
knowledge <strong>of</strong> the dynamics <strong>of</strong> the spread <strong>of</strong> prions in vivo, the pathogenesis studies also
provided the evidence for the development <strong>of</strong> the initial Over Thirty Month Scheme (OTMS),
whereby the UK Government was able to purchase, for slaughter and ultimate destruction,
cattle which were over 30 months <strong>of</strong> age. This implemented EU Regulations that ordered the
prevention <strong>of</strong> the sale <strong>of</strong> beef from cattle over this age for human consumption in the UK.
<strong>The</strong> OTMS was a crucial element <strong>of</strong> legislation for public health, and it may well have averted
a larger number <strong>of</strong> vCJD cases than experienced so far. 21
BSE pathogenesis studies in sheep – a model for vCJD
6.23 Sheep are susceptible to infection with the BSE agent, and the dynamics <strong>of</strong> infection and spread
<strong>of</strong> prions in peripheral tissues is similar to that <strong>of</strong> vCJD in humans. Thus sheep are commonly
held to be a useful model for vCJD. Studies <strong>of</strong> scrapie in sheep were the first to show that prions
could accumulate in the tonsils, and this was shown subsequently to be the case for vCJD. <strong>The</strong>re
followed an analysis <strong>of</strong> the prevalence <strong>of</strong> vCJD in the human population through retrospective
studies on tonsils, and later appendices. <strong>The</strong> results provided the first information on the
number <strong>of</strong> people that could be incubating the disease.
6.24 BSE pathogenesis studies in sheep also showed that blood can be infectious. BSE can be
transmitted between sheep by blood transfusion and current experiments are aimed at
identifying the blood fraction that contains infectivity. Scientists conducting these
experiments are also interested in exploring the implications <strong>of</strong> human-to-human
transmission <strong>of</strong> vCJD through blood and have guided UK policy for public health by limiting
the potential for this type <strong>of</strong> spread <strong>of</strong> vCJD. In 2003, it was found likely that two people
who died <strong>of</strong> vCJD were infected by blood transfusions. As a result, the Department <strong>of</strong> Health
announced in 2004 that anyone who had received a blood transfusion in the UK since 1980
would no longer be able to donate blood themselves. 22
<strong>The</strong> discovery <strong>of</strong> the hepatitis C virus using the chimpanzee
6.25 We now consider a more historic example <strong>of</strong> animal <strong>research</strong> for the study <strong>of</strong> disease. <strong>The</strong>
existence <strong>of</strong> a blood-borne hepatitis virus that was neither type A nor B was described in the
1970s, following the identification <strong>of</strong> both these types. Throughout the 1980s, assays were
developed to try and identify the cause <strong>of</strong> what was then termed non-A, non-B (NANB)
hepatitis. However, none <strong>of</strong> the tests were sufficiently reproducible or specific. 23 <strong>The</strong>refore
an experimental chimpanzee model was developed, as this species was the only non-human
animal that could be infected with the NANB hepatitis agent, which is still not able to be
propagated in vitro. <strong>The</strong> chimpanzee model was used to demonstrate that NANB hepatitis
was indeed transmissible, and allowed the isolation and characterisation <strong>of</strong> the virus. 24
CHAPTER 6 THE USE OF ANIMALS IN THE STUDY OF HUMAN DISEASE
21 In 2004–5, the UK Government is implementing a transition towards replacing the OTMS with testing for BSE in cattle <strong>of</strong>
over thirty months <strong>of</strong> age. See Department for Environment, Food and Rural Affairs (2005) BSE: Public health issues – Over
Thirty Month cattle – FSA review <strong>of</strong> the OTM rule, available at:
http://www.defra.gov.uk/animalh/bse/publichealth/otm/review/index.html. Accessed on: 26 Apr 2005.
22 National Blood Service (2004) Variant CJD and blood donation, available at: http://www.blood.co.uk/pdfdocs/vcjd.pdf.
Accessed on: 26 Apr 2005.
23 Farci P (2002) A commentary on the original Science paper (Choo QL, Kuo G, Weiner AJ et al. (1989) Isolation <strong>of</strong> a cDNA
clone derived from a blood-borne non-A, non-B viral hepatitis genome Science 244: 359–62) J Hepatol 36: 582–5.
24 Farci P (2002) A commentary on the original Science paper (Choo QL, Kuo G, Weiner AJ et al. (1989) Isolation <strong>of</strong> a cDNA
clone derived from a blood-borne non-A, non-B viral hepatitis genome Science 244: 359–62) J Hepatol 36: 582–5.
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