Scrapie

Contaminated Louping-ill vaccine.  Also known as the 1935 Moredun Louping-ill Vaccine Disaster..[33]  More than 1,500 sheep developed scrapie following vaccination. "An investigation into the etiology of scrapie followed the vaccination of sheep for louping-ill virus with formalin-treated extracts of ovine lymphoid tissue unknowingly contaminated with scrapie prions (Gordon 1946). Two years later, more than 1500 sheep developed scrapie from this vaccine." [34]  "This vaccine was manufactured using formalised sheep brains contaminated with scrapie agent" [35]  "At the 1946 National Veterinary Medical Association of Great Britain and Ireland Annual Congress, W. S. Gordon, PhD, presented evidence of scrapie transmission by way of a vaccine for louping-ill." "Dr. Gordon developed an effective vaccine to prevent louping-ill during 1931-32. After four years of field trials, his vaccine was produced in three batches for widespread use in 1935. The vaccine was made from brain, spinal cord, and spleen tissues taken from sheep five days after they had received an intracerebral inoculation of louping-ill virus. Formalin was added to the 10% saline suspension to inactivate the virus.  During 1935 and 1936, no ill effects were noted in inoculated animals. Then two owners reported scrapie in their Blackface sheep who had been inoculated with louping-ill vaccine (batch 2) two and a half years earlier. Scrapie had not been seen in the Blackface breed before this. Upon investigation Dr. Gordon discovered that 8 lambs used to make batch 2 had been born to ewes who had been exposed to scrapie; some of the ewes developed scrapie in 1936-7. Dr. Gordon hypothesized that an "infective agent of scrapie" was present in the lambs' tissues used to make batch 2 and that this agent "could withstand a concentration of formalin...which inactivated the virus of louping ill; it could be transmitted by subcutaneous inoculation; it had an incubative period of two years or longer."  A four-and-a-half-year experiment involving '788 sheep was initiated by the Animal Disease Research Association in 1938. The researchers found that 60% of normal sheep inoculated intracerebrally with saline suspensions of brain and spinal cord tissue taken from sheep with scrapie developed scrapie within those four-and-a-half-years. The incubation period was seven months and up. Only 30% of the sheep receiving a subcutaneous inoculation of the suspension developed scrapie in that time, and the incubation period in this group was 15 months and up. The researchers concluded that the infective agent was probably a filtrable virus." [36]
Contaminated Mycoplasma agalactiae vaccine. In 1997 and 1998 there was an outbreak of scrapie in sheep and goats in Italy, and the cause was attributed to the vaccine. "An accidental infection from a vaccine was suggested as the explanation for the sudden increase in outbreaks of scrapie in Italy in 1997 and 1998. This paper describes a recent outbreak of scrapie in sheep and goats which were exposed to the same vaccine. No ewes or goats had been imported into the herd since 1992, but a vaccine against Mycoplasma agalactiae had been administered twice, in 1995 and 1997. High rates of crude mortality and scrapie incidence were experienced by both species, all birth cohorts were involved and a large proportion of aged animals was affected. A pattern of brain lesions was observed, with slight differences between the sheep and goats, which was very similar to the pattern observed in animals previously exposed to the same vaccine but clearly different from that observed in the brains of sheep with scrapie in a flock not exposed to the vaccine. Regardless of their exposure status, genotype analysis of the sheep showed the presence of polymorphism only at codon 171. The patterns of both incidence and brain lesions provide evidence that the epidemic of scrapie was due to the use of the vaccine." [37]  "An accidental intra- and interspecies transmission of scrapie occurred in Italy in 1997 and 1998 following exposure to a vaccine against Mycoplasma agalactiae. PrP(Sc) in affected sheep and goats, collected from a single flock exposed to vaccination 2 years earlier, was molecularly typed. In five animals with iatrogenic scrapie, a PrP(Sc) type with a 20 kDa core fragment was found in all areas of the brain investigated. In three sheep and one goat, this isoform co-occurred with a fully glycosylated isoform that had a protease-resistant backbone of 17 kDa, whereas in two sheep and four goats, the two PrP(Sc) types were detected in different regions of the brain. In sheep with natural field scrapie, a PrP(Sc) type with physico-chemical properties indistinguishable from the 20 kDa isoform was found. The present results suggest the co-presence of two prion strains in mammary gland and brain homogenates used for vaccination." [38][39]

Question: Why is Scrapie called such?