Abstract
Introduction. In the Netherlands an ambitious scrapie control
program was started at the national level in 1998, based on
genetic selection of animals for breeding. From 2002 onwards
EU regulations required intensive active scrapie surveillance as
well as certain control measures in affected flocks.
Materials and Methods. Here we use standard statistical
methods as well as mathematical modeling to analyze (1) data
on genotype frequencies and scrapie prevalence in the Dutch
sheep population obtained from both surveillance and affected
flocks; (2) data on PrP genotype frequencies in a random sample
of flocks; (3) postal survey results on between-flock differences in
breeding strategy and flock management.
Results and Conclusions. Analyzing the data (1) we find that
the breeding program has produced a steady increase in the level
of genetic scrapie resistance in the Dutch sheep population. We
also found that a few years later this was followed by a sharp
decline in the prevalence of classical scrapie in tested animals.
Notably, the estimated classical scrapie prevalence level per head
of susceptible genotype declined significantly as well. This indicates
that selective breeding has a disproportionate effect on
infection prevalence, reminiscent of the well-known population
effect of vaccination against a transmissible disease. The overall
recent decline in classical scrapie prevalence in Dutch sheep suggests
that eradication of the disease in The Netherlands may be
within reach. However, a subset of farms may still continue to
act as a core group for scrapie transmission for some time, as we
show by analyzing between-flock heterogeneities using the data
(2) and (3). In addition, genetic resistance levels may decline
again in future as participation to the selective breeding program
has recently become voluntary.
Original language | English |
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Title of host publication | Prion 6, Amsterdam, The Netherlands, 10-12 May 2012 |
Publisher | Landes Bioscience |
Pages | 72-73 |
Volume | 6 |
Publication status | Published - 2012 |
Event | Prion 2012, Amsterdam, The Netherlands - Duration: 10 May 2012 → 12 May 2012 |
Conference/symposium
Conference/symposium | Prion 2012, Amsterdam, The Netherlands |
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Period | 10/05/12 → 12/05/12 |