121
form is probably a receptor.6) The misshapen protein molecules clump together and accu-
mulate in brain tissue, causing a severe loss of neurons, gliosis (excessive development of
neuroglia tissue) and a spongiform appearance. All of the diseases have a long incubation
period and lead to dementia and death. There is no treatment and, thus, no cure.7
Kuru, the first human malady to be labeled a slow virus disease, came to the attention
of Western doctors only in the 1950s: it was the primary cause of death among the Fore, a
cannibalistic New Guinea tribe. In 1966, Carleton Gajdusek and Joe Gibbs proved that like
scrapie, kuru was infectious chimps inoculated with the brain tissue of human victims
developed kuru-like symptoms and died. The spread of the disease was attributed to the
endocannabalistic funeral practices of the tribe in which relatives prepared and consumed
the tissues (including the brain) of deceased family members.8 Male members of the Fore
tribe participated little, if at all, in these feasts, with the result that kuru at its peak pre-
dominantly affected women and children.
Classic Creutzfeldt-Jakob disease is the most prevalent of the spongiform diseases. It
occurs spontaneously in one out of a million people, 10% of whom inherited mutations in
the prion protein gene (PRPN). The disease was first described by Alfons Jakob in 1920 in
a paper published in a German medical journal.9 The patient in the report was a 22-year-
old woman being treated for a progressive dementing illness. Jakob described four older
patients with a clinically similar presentation and course one year later, and during the
ensuing decades, numerous cases of the disease were described clinically and pathologi-
cally.10 In 1959, Klatzo et al. noted the neuropathological similarities between CJD and
kuru.11 That same year, Hadlow described the similarities between kuru and scrapie, and
suggested that kuru might be transmissible to animals after a long incubation period.12
During the next decade, both kuru and CJD were transmitted to apes and monkeys.13
New variant Creutzfeldt-Jakob disease differs dramatically from classic CJD. In
patients with vCJD, symptoms develop at a mean age of 26 years—nearly four decades
earlier than patients with the classic sporadic disease. The new variant was linked to
exposure to BSE, or “mad cow” disease, in British beef. During the period from November
1986 (when BSE was first identified as a separate disease entity) until December 1995, an
estimated 155,600 head of cattle in almost 33,000 herds were diagnosed with BSE in the
UK. The epidemic peaked in January 1993 at almost 1,000 new cases per week. As of 2004,
it was estimated that four million cattle were infected over the course of the BSE epidemic
and there were 155 vCJD cases worldwide, all of whom have died. The only affected US
resident, whose probable vCJD case was identified in 2002, was a 22-year-old woman who
had moved from the UK to Florida in 1992.14 Because of the long incubation period, cases
due to mad cow beef will likely surface well into the future.15
Regulatory Issues
On 20 March 1996, the British government announced that new information about BSE
suggested a possible relationship between the disease and 10 cases of a newly identified
form of CJD in humans. The US Food and Drug Administration (FDA), on 9 May 1996,
issued a notice to manufacturers of drug/biological/device products recommending
avoidance of materials from cattle born, raised or slaughtered in countries where BSE
was known to exist. The agency stated its belief that the rapid spread of BSE in cattle was
caused by feeding them certain infected cattle and sheep tissues.
FDA has published two rules to protect animals and consumers against BSE. The
1997 final regulation prohibited the use of most mammalian protein in feed given to
cows, sheep and goats, and required process and control systems to ensure that feed does
not contain the prohibited tissue. This rule, Title 21 Part 589.200, called the Ruminant
Feed Ban, became effective on 4 August 1997. In 2008, FDA published a regulation that
strengthened the 1997 rule by prohibiting the use of certain cattle-derived materials that
have the highest risk for carrying the agent thought to cause BSE. These materials are the
Prions—Still a Mystery!
form is probably a receptor.6) The misshapen protein molecules clump together and accu-
mulate in brain tissue, causing a severe loss of neurons, gliosis (excessive development of
neuroglia tissue) and a spongiform appearance. All of the diseases have a long incubation
period and lead to dementia and death. There is no treatment and, thus, no cure.7
Kuru, the first human malady to be labeled a slow virus disease, came to the attention
of Western doctors only in the 1950s: it was the primary cause of death among the Fore, a
cannibalistic New Guinea tribe. In 1966, Carleton Gajdusek and Joe Gibbs proved that like
scrapie, kuru was infectious chimps inoculated with the brain tissue of human victims
developed kuru-like symptoms and died. The spread of the disease was attributed to the
endocannabalistic funeral practices of the tribe in which relatives prepared and consumed
the tissues (including the brain) of deceased family members.8 Male members of the Fore
tribe participated little, if at all, in these feasts, with the result that kuru at its peak pre-
dominantly affected women and children.
Classic Creutzfeldt-Jakob disease is the most prevalent of the spongiform diseases. It
occurs spontaneously in one out of a million people, 10% of whom inherited mutations in
the prion protein gene (PRPN). The disease was first described by Alfons Jakob in 1920 in
a paper published in a German medical journal.9 The patient in the report was a 22-year-
old woman being treated for a progressive dementing illness. Jakob described four older
patients with a clinically similar presentation and course one year later, and during the
ensuing decades, numerous cases of the disease were described clinically and pathologi-
cally.10 In 1959, Klatzo et al. noted the neuropathological similarities between CJD and
kuru.11 That same year, Hadlow described the similarities between kuru and scrapie, and
suggested that kuru might be transmissible to animals after a long incubation period.12
During the next decade, both kuru and CJD were transmitted to apes and monkeys.13
New variant Creutzfeldt-Jakob disease differs dramatically from classic CJD. In
patients with vCJD, symptoms develop at a mean age of 26 years—nearly four decades
earlier than patients with the classic sporadic disease. The new variant was linked to
exposure to BSE, or “mad cow” disease, in British beef. During the period from November
1986 (when BSE was first identified as a separate disease entity) until December 1995, an
estimated 155,600 head of cattle in almost 33,000 herds were diagnosed with BSE in the
UK. The epidemic peaked in January 1993 at almost 1,000 new cases per week. As of 2004,
it was estimated that four million cattle were infected over the course of the BSE epidemic
and there were 155 vCJD cases worldwide, all of whom have died. The only affected US
resident, whose probable vCJD case was identified in 2002, was a 22-year-old woman who
had moved from the UK to Florida in 1992.14 Because of the long incubation period, cases
due to mad cow beef will likely surface well into the future.15
Regulatory Issues
On 20 March 1996, the British government announced that new information about BSE
suggested a possible relationship between the disease and 10 cases of a newly identified
form of CJD in humans. The US Food and Drug Administration (FDA), on 9 May 1996,
issued a notice to manufacturers of drug/biological/device products recommending
avoidance of materials from cattle born, raised or slaughtered in countries where BSE
was known to exist. The agency stated its belief that the rapid spread of BSE in cattle was
caused by feeding them certain infected cattle and sheep tissues.
FDA has published two rules to protect animals and consumers against BSE. The
1997 final regulation prohibited the use of most mammalian protein in feed given to
cows, sheep and goats, and required process and control systems to ensure that feed does
not contain the prohibited tissue. This rule, Title 21 Part 589.200, called the Ruminant
Feed Ban, became effective on 4 August 1997. In 2008, FDA published a regulation that
strengthened the 1997 rule by prohibiting the use of certain cattle-derived materials that
have the highest risk for carrying the agent thought to cause BSE. These materials are the
Prions—Still a Mystery!