No evidence indicates that scrapie is a risk to humans or other livestock (other than goats). Cattle could not be infected with scrapie orally, and although cattle experimentally infected with scrapie via injection directly into the brain developed clinical signs, the direct injection of scrapie into the brain doesn’t indicate an ability to infect cattle naturally.15 Nonetheless, scrapie constitutes a $20 million to $25 million loss to U.S. producers, primarily due to trade restrictions in foreign markets.16
As with other TSEs, no effective treatments or vaccines are yet available for scrapie. Therefore, control efforts have focused on import restrictions, identifying and depopulating infected animals and selectively breeding for scrapie resistance.
The European Union has breeding programs in place to encourage the prevalence of scrapie-resistant genotypes in their respective herds.17 While the United States doesn’t have an official breeding program concerning resistant genotypes, some U.S. producers have implemented breeding programs. However, the discovery of “atypical” forms of scrapie in animals with classical scrapie-resistant genotypes may mean that selective breeding programs need to be adjusted to address atypical forms of scrapie in addition to classical scrapie.18
The United States also has an accelerated scrapie eradication program based on the following key concepts:1
- Identification of preclinical infected sheep through live animal testing and active harvest surveillance,
- Effective tracing of infected animals to their flock/herd of origin made possible as a result of the identification requirements,
- Providing effective genetic-based flock cleanup strategies that will allow producers to stay in business preserve breeding stock and remain economically viable. APHIS provides the following to exposed and infected flocks/herds that participate in cleanup or monitoring plans:
- Indemnity for high-risk, suspect, and scrapie positive sheep and goats, which owners agree to destroy,
- Scrapie live-animal testing,
- Genetic testing, and
- Testing of exposed animals that have been sold out of infected and source flocks/herds.
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