Experience with index selection in icelandic sheep

Experimental visna in Icelandic sheep: the prototype lentiviral infection.

A brief review of experimental infection of Icelandic sheep following intracerebral inoculation of neurotropic strains of visna virus is presented. In vivo replication of the virus is restricted, so that some cells carry the deoxyribonucleic acid provirus as an unexpressed genome. This cellular restriction plays a major role in the slow progression of the infection, abetted by neutralizing anti...

PrP gene polymorphism and natural scrapie in Icelandic sheep.

The association between scrapie and polymorphism of the prion protein (PrP) gene was studied in the Icelandic sheep breed. Polymorphism of the three codons, 136, 154 and 171, that are important for scrapie susceptibility was determined. A BspHI restriction analysis was used to study the alleles of codons 136 and 154, while density gradient gel electrophoresis (DGGE) was used to analyse codon 17...

Estimating stability and selection index

Antigenic drift in visna: virus variation during long-term infection of Icelandic sheep.

A group of 20 Icelandic sheep were infected intracerebrally with visna virus strain 1514, and 209 virus isolates were obtained from the blood, cerebrospinal fluid, and central nervous system (CNS) over a period of 7 years, during which eight animals developed clinical signs of visna necessitating sacrifice. (i) Using type-specific antisera, it was found that 12 (16%) of 76 isolates tested escap...

Iron and iron/manganese ratio in forage from Icelandic sheep farms: relation to scrapie

This study was undertaken in order to examine whether any connection existed between the amounts of iron in forage and the sporadic occurrence of scrapie observed in certain parts of Iceland. As iron and manganese are considered antagonistic in plants, calculation of the Fe/Mn ratios was also included by using results from Mn determination earlier performed in the same samples. Forage samples (...