Glutathione peroxidase (GPX) activity in blood of ewes on farms in different scrapie categories in Iceland

Kristín B Gudmundsdóttir¹^,4 , Jakob Kristinsson² , Sigurdur Sigurdarson¹^,5 , Tryggvi Eiríksson³ and Torkell Jóhannesson²

¹Chief Veterinary Office, Section for Animal Diseases, Institute for Experimental Pathology, University of Iceland, Keldur v/Vesturlandsveg, 110 Reykjavík, Iceland

²Department of Pharmacology and Toxicology, Institute of Pharmacy, Pharmacology and Toxicology, University of Iceland, Hofsvallagata 53, 107 Reykjavík, Iceland

³Faculty of Natural Resources, Agricultural University of Iceland, Keldnaholt, 112 Reykjavík, Iceland

⁴Actavis Group, Clinical Research Department, Reykjavíkurvegur 80, 220 Hafnarfjördur, Iceland

⁵The Icelandic Food and Veterinary Authority, Austurvegur 64, 800 Selfoss, Iceland

author email corresponding author email

Acta Veterinaria Scandinavica 2008, 50:23doi:10.1186/1751-0147-50-23


Published:	23 June 2008

Abstract

Background

Preliminary studies indicated decreased glutathione peroxidase (GPX) activity in blood of ewes on scrapie-afflicted farms. Other studies have shown decreased GPX activity in brain of prion-infected mice and in prion-infected cells in vitro. The aim of this study was to examine the GPX activity in blood as well as the distribution of GPX-activity levels from ewes on farms in scrapie-afflicted areas in Iceland.

Methods

Blood samples were collected from 635 ewes (non-pregnant [n = 297] and pregnant [n = 338]) on 40 farms in scrapie-afflicted areas during the years 2001–2005, for analysis of GPX activity. The farms were divided into three categories: 1. Scrapie-free farms (n = 14); 2. Scrapie-prone farms (earlier scrapie-afflicted, restocked farms) (n = 12); 3. Scrapie-afflicted farms (n = 14). For comparison, 121 blood samples were also collected from non-pregnant ewes on one farm (farm A) in a scrapie-free area (scrapie never registered). Chi-square test was used to test for normal distribution of GPX-results, and Kruskal-Wallis test to compare GPX-results between categories.

Results

The GPX-results appeared to be biphasically distributed in ewes in all three scrapie categories and on farm A. The presumptive breaking point was about 300 units g Hb^-1. About 30–50% of the GPX-results from ewes in all three scrapie categories were below 300 units g Hb^-1but only about 13% of the GPX-results from ewes on farm A. The mean GPX activity was highest on farm A, and was significantly lower on scrapie-prone farms than on scrapie-free or scrapie-afflicted farms (non-pregnant and pregnant ewes: P < 0.005, respectively; non-pregnant and pregnant ewes combined: P < 0.0005).

Conclusions

1) the distribution of GPX-results in blood of Icelandic ewes apparently has a biphasic character; 2) the GPX-results were higher in ewes on one farm in a scrapie-free area than in ewes on farms in the scrapie-afflicted areas; 3) GPX-activity levels were significantly lowest on earlier scrapie-afflicted, restocked farms, which might have a bearing on the recurrence of sporadic scrapie on these farms; 4) further study on the possible role of GPX activity in the occurrence of scrapie in Iceland is warranted.