Individual viruses have evolved interesting and unique lifestyles. One consequence is that battles have been won or lost when a particular virus infected one army but not its opponent. Viruses have wiped out native populations of several continents. Entire countries have been changed geographically, economically, and religiously as a result of virus infections with no known cures. Spongiform Encephalopathies (Bovine, BSE), a somewhat new virus most common in cattle has been closely linked to Kuru, Scrapie, and CJD.
Over 200 years ago farmers in England, Scotland, and France noted that some sheep suffered a progressive loss of balance, shaking, wasting, and sever itching that caused them to rub their hinds and flanks against any upright post. The name scrapie, was given to this disorder. Owners of healthy flocks noticed that their animals contracted scrapie only after introduction of a new breeding stock later found to bear the disease. Eventually sheep exported from England infected herds in Australia, New Zealand, and South Africa. Only extermination of the affected animals stopped scrapie from spreading, but by then it was distributed widely throughout Europe, Asia, and America. In the 1930’s, J. Cuillé provided evidence for the first transmission of scrapie to a healthy sheep and documented that the agent was in brain extracts taken from scrapie-infected sheep and passed through filters with pores small enough to retain all microbes but viruses and perhaps other yet to be identified agents.
At about the same time and into the 1960’s, a disease among the isolated Fore tribespeople in the central New Guinea highlands, an area under Australian administration, was investigated by Drs. Vincent Zigas and D. Carlton Gajdusek:

In 1957, Dr. Vincent Zigas and I first described the rapidly fatal disease, kuru, a strong, new subacute, familial, degenerative disease of the central nervous system.
On first seeing kuru, we had suspected it to be a viral meningeoncephalitis, only
to find very little in the clinical picture, laboratory findings, or epidemiology, to
support such a suspicion. We had early considered association of the disease with
extensive cannibalism, but soon dismissed this as unlikely when cases of the
disease were encountered in individuals whom we did not believe had engaged in
the ritual cannibalistic consumption of diseased relatives, the prevailing practice in
the region.

Kuru, which means shivering or trembling in the Fore language, was characterized primarily as a disease of women and children. Those afflicted had tremors, loss of balance, and an inability to form words, leading to a total loss of speech. Death followed usually in less that one year from the onset of obvious symptoms. This disease was common both in male and female children and in adult females, but rare in adult males. The disease was transmitted by the practice of ritual cannibalism, a rite of mourning and respect for dead kinsman in which several tissues, including what we now know was highly infectious brain matter, were consumed by women and small children.
The pathologic similarity of kuru and scrapie to Creutzfeldt-Jakob disease (CJD), known previously as a chronic progressive dementia of humans tormented by tremors, led to the concept that a whole group of diseases involving slow progression and injury of nerve cells might be related. These lethal diseases were called spongiform encephalopathies. In the laboratory, these diseases of sheep and humans were transmissible by feeding or inoculation, and had incubation periods varying from a few months to years, depending primarily on dose and strain of inoculum and genetics of the host. The infectious factor had at least one aspect of a virus, but it differed from viruses by virtue of its resistance to inactivation by treatments known to kill viruses such as boiling, application of 70 percent ethanol, ionizing and ultraviolet radiation, and the lack of an identifiable nucleic acid.
In 1985-86, bovine spongiform encephalopathy (BSE) in cattle was first identified in southern England, and within two years over 1000 cases surfaced in more that 200 herds. This was clearly a new disease in cattle, and by 1996 there have been over 160,000 confirmed cases in the U.K. affecting 59 percent of dairy herds as reported by the British Government’s Ministry of Agriculture, Fisheries and Food. However, the data from 1988 to 1996 was hidden by the British Government and denied to non-government researchers. When the information