TSE eradication in small ruminants--quo vadis?

Area of Science:

• Veterinary Medicine
• Infectious Diseases
• Animal Health

Background:

• Transmissible Spongiform Encephalopathies (TSEs) encompass Bovine Spongiform Encephalopathy (BSE) and classical/atypical scrapie in sheep and goats.
• TSE pathogenesis in small ruminants differs from bovines, with peripheral tissues becoming infectious early.

Purpose of the Study:

• To highlight fundamental differences in TSE infections between small and large ruminants.
• To discuss the implications for animal and human health protection strategies.
• To evaluate current TSE eradication measures in light of new findings.

Main Methods:

• Comparative analysis of TSE pathogenesis and transmission in small ruminants versus bovines.
• Review of regulatory measures for BSE and scrapie control.
• Assessment of atypical scrapie cases and their impact on eradication strategies.

Main Results:

• Small ruminant TSEs show distinct pathogenesis, with peripheral infectivity preceding clinical signs.
• Classical scrapie transmits horizontally within sheep flocks.
• BSE presents a higher zoonotic risk than scrapie, necessitating different control measures.
• Atypical scrapie cases exhibit divergent characteristics, challenging existing eradication protocols, particularly genotype-based culling.

Conclusions:

• Eradication of BSE and classical scrapie in small ruminants requires stringent strategies, including culling susceptible animals.
• The emergence of atypical scrapie complicates eradication efforts and questions the efficacy of current selective breeding and culling methods.
• Differentiated regulatory approaches are crucial for managing BSE and scrapie in large versus small ruminants to protect animal and human health.