Survey of natural scrapie in Japan: analysis of RFLP types of the PrP gene and detection of PrPSc mainly in Suffolk sheep.

Abstract

We examined the brains, spleens and/or lymph nodes of 197 mainly suffolk sheep collected from Hokkaido, and the Tohoku, Kanto and Chubu districts to detect PrPSc and thus to estimate scrapie contamination in Japan. Sixteen sheep in Hokkaido and 2 sheep in other districts that were introduced from Hokkaido were positive for PrPSc. By comparison of the frequencies of the restriction fragment length polymorphism (RFLP) types of these 18 scrapie sheep with 128 healthy sheep, we confirmed the association of specific RFLP types of the PrP gene with natural scrapie. The frequency of RFLP type I in scrapie sheep was significantly higher than that in healthy sheep and those of other types in scrapie sheep. In contrast, the frequencies of type II and VI in healthy sheep were higher than those in scrapie sheep. Therefore, type I sheep seemed to be susceptible but type II and VI sheep seemed to be resistant to natural scrapie in Suffolk sheep in Japan. Furthermore, we investigated the distribution of the RFLP types of the PrP gene in 161 sheep in Japan to learn about the genetic background of the susceptibility to scrapie. There were variations in the distribution of the RFLP types in each district.