Eradication of ovine scrapie TSE through selective genetics using a two-flock model

The efficiency of eradicating scrapie from an infected flock using selective genetics will be determined using a flock of naturally exposed sheep held in typical production setting. BSL-1; 9-4-02. Documents SCA with N. Dakota State University.
<p>
4. What were the most significant accomplishments this past year? <br>
D. Susceptibility to scrapie is controlled by polymorphisms in the PRNP gene, with susceptibility associated with an allele encoding valine (V) at codon 136 (formerly strain A scrapie) or with homozygosity for the allele encoding glutamine (Q) at codon 171 (formerly strain C scrapie). Resistance is seen in adult animals subjected to natural or experimental exposure. </p>
<P>
In addition, fetal placental tissue with the heterozygous resistant genotype (QR) in bred susceptible ewes (QQ) does not contain detectable PrP-Sc, the marker for disease. In collaboration with North Dakota State University, we have characterized the epidemiology of a major outbreak of scrapie in the valine-related scrapie strain, the only such well-documented outbreak in the US. Transmission patterns suggest efficient spread of the disease among adults.</p>
<P>
In addition, NDSU serves as the site for a study investigating the placentas of susceptible (QQ) fetuses in resistant (QR) ewes; the ewes themselves are progeny of infected QQ ewes. </p>
<P>
The experiment will test the hypothesis that the ewes are free from disease, rather than silent carriers. The QR progeny of infected dams are removed to the QR breeding study at Hettinger, ND. These ewes will be bred to susceptible (QQ) rams, producing both resistant (QR) and susceptible (QQ) progeny. All placentas from these ewes will be examined for PrP-Sc and all QQ progeny will be held in long term quarantine and monitored for scrapie. </p>
<P>
This report serves to document research conducted under a specific cooperative agreement between ARS and North Dakota State University. Additional details of research can be found in the report for the parent project 5348-32000-019- 00D Animal Health. </p>