News briefing： Itching disease is an infectious spongiform encephalopathy, which can be transmitted in susceptible sheep.

Itching disease is an infectious spongiform encephalopathy, which can be transmitted in susceptible sheep. Prion protein gene (PRNP) profoundly affects the sensitivity of sheep to itch agents. This study reported that PrP (Sc) could not be detected in nerve or lymph tissues of Suffolk sheep with ARQ/ARR PRNP genotype after oral inoculation of American itch bacteria strain.

Lambs were inoculated with 1ml of 10% (weight/volume) brain homogenate from clinically affected ARQ/ARQ sheep for the first time at 24h of birth. During the whole experiment period, the clinical features of sheep itch disease inoculated were observed daily until it was anatomized 86 months after the second inoculation. Immunohistochemical and enzyme-linked immunosorbent assay were used to detect the tissue samples, and no evidence proving the infection of scrapie was found. Newborn sheep with ARQ/ARQ genotype were infected with itchy disease within 24 months after oral administration of the same inoculum. The ARQ/ARR genotype lambs inoculated with the same inoculum in the brain were also infected with itch, but the incubation period was prolonged, and there were abnormal prions in the central nervous system, but not in the peripheral lymphoid tissues. The results of this study show that the resistance of ARQ/ARR sheep to oral infection with itchy bacteria strain has been produced in the neonatal period.