Infectivity studies of both ash and air emissions from simulated incineration of scrapie-contaminated tissues.

We investigated the effectiveness of 15 min exposures to 600 and 1000 degrees C in continuous flow normal and starved-air incineration-like conditions to inactivate samples of pooled brain macerates from hamsters infected with the 263K strain of hamster-adapted scrapie with an infectivity titer in excess of 10(9) mean lethal doses (LD50) per g. Bioassays of the ash, outflow tubing residues, and vented emissions from heating 1 g of tissue samples yielded a total of two transmissions among 21 inoculated animals from the ash of a single specimen burned in normal air at 600 degrees C. No other ash, residue, or emission from samples heated at either 600 or 1000 degrees C, under either normal or starved-air conditions, transmitted disease. We conclude that at temperatures approaching 1000 degrees C under the air conditions and combustion times used in these experiments, contaminated tissues can be completely inactivated, with no release of infectivity into the environment from emissions. The extent to which this result can be realized in actual incinerators and other combustion devices will depend on equipment design and operating conditions during the heating process.

Human spongiform encephalopathy: the National Institutes of Health series of 300 cases of experimentally transmitted disease

We present a synthesis of clinical, neuropatholgical, and biological details of the National Institutes of Health series of 300 experimentally transmitted cases of spongiform encephalopathy from among more than 1,000 cases of various neurological disorder inoculated into nonhuman primates during the past 30 years. The series comprises of 278 subjects with Creutzfeldt-Jakob disease, of whom 234 had sporadic, 36 familial, and 8 iatrogenic disease; 18 patients with kuru; and 4 patients with Gerstmann-Straussler-Scheinker syndrome. Sporadic Creutzfeldt-Jakob disease, numerically by far the most important representative, showed an average age at onset of 60 years, with the frequent early appearance of cerebellar and visual/oculomotor signs, and a broad spectrum of clinical features during the subsequent course of illness, which was usually fatal in less than 6 months. Characteristic spongiform neuropathology was present in all but 2 subjects. Microscopically visible kuru-type amyloid plaques were found in 5 percent of patients with Creutzfeldt-Jakob disease. 75 percent of those with kuru, and 100 percent of those with Gerstmann-Straussler-Scheinker syndrome; brain biopsy was diagnostic in 95 percent of cases later confirmed at autopsy, and proteinase-resistant amyloid protein was identified in Western blots of brain extracts from 88 percent of tested subjects. Experimental transmission rates were highest for iatrogenic Creutzfeldt-Jakob disease (100 percent), kuru (95 percent), and sporadic Creutzfeldt-Jakob disease (90 percent), and considerably lower for most familiar forms of disease (68 percent). Incubation periods as well as the durations and character of illness showed great variability, even in animals receiving the same inoculum, mirroring the spectrum of clinical profiles seen in human disease. Infectivity reached average levels of nearly 10(to the 5th power) median lethal doses/gm of brain tissue, but was only irregularly present (and at much lower levels) in tissues outside the brain, and, except for cerebrospinal fluid, was never detected in bodily secretions or excretions (AU)