Journal Article

Autoclave treatment of the classical scrapie agent US No. 13-7 and experimental inoculation to susceptible VRQ/ARQ sheep via the oral route results in decreased transmission efficiency

Cassmann, Eric D., Mammadova, Najiba, Greenlee, Justin J.

2020

Overview

Scrapie, a prion disease of sheep, is highly resistant to conventional deactivation. Numerous methods to deactivate scrapie have been tested in laboratory animal models, and adequate autoclave treatment can reduce or remove the infectivity of some classical scrapie strains depending on the heating parameters used. In this study, we autoclaved brain homogenate from a sheep with US scrapie strain 13–7 for 30 minutes at 121°C. Genetically susceptible VRQ/ARQ sheep were orally inoculated with 3 grams of the autoclaved brain homogenate. For comparison, a second group of sheep was inoculated with a non-autoclaved brain homogenate. Rectal biopsies were used to assess antemortem scrapie disease progression throughout the study. Five out of ten (5/10) sheep that received autoclaved inoculum ultimately developed scrapie after an experimental endpoint of 72 months. These sheep had a mean incubation period of 26.99 months. Two out of five (2/5) positive sheep had detectable PrP Sc in antemortem rectal biopsies, and two (2/5) other sheep had PrP Sc in postmortem rectal tissue. A single sheep (1/5) was positive for scrapie in the CNS, small intestine, and retropharyngeal lymph node but had negative rectal tissue. All of the sheep (10/10) that received non-autoclaved inoculum developed scrapie with a mean incubation period of 20.2 months and had positive rectal biopsies at the earliest timepoint (14.7 months post-inoculation). These results demonstrate that sheep are orally susceptible to US derived classical scrapie strain 13–7 after autoclave treatment at 121°C for 30 minutes. Differences in incubation periods and time interval to first positive rectal biopsies indicate a partial reduction in infectivity titers for the autoclaved inoculum group.

• Publisher: Public Library of Science,Public Library of Science (PLoS)
• Subject: Administration, Oral / Agricultural research / Analysis / Animal diseases / Animal models / Animals / Autoclaves / Automation / BASIC BIOLOGICAL SCIENCES / Biology and Life Sciences / Biopsy / Brain / Brain - metabolism / Brain - pathology / Care and treatment / Control / Deactivation / Diagnosis / Disease transmission / Distribution / Enzymes / Genetic susceptibility / Immunoassay / Infectious Disease Incubation Period / Infectivity / Inoculation / Inoculum / Intestine / Laboratory animals / Lymph nodes / Medical research / Medicine and Health Sciences / Oral administration / Phosphatase / PrPSc Proteins - administration & dosage / PrPSc Proteins - chemistry / PrPSc Proteins - pathogenicity / Rectum / Science & Technology - Other Topics / Scrapie / Scrapie - mortality / Scrapie - pathology / Scrapie - transmission / Sheep / Sheep - genetics / Small intestine / Sterilization - methods / Transmission efficiency