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How BSE Affects Cattle: Cellular Targets, Neuroinvasion, and Zoonotic Risk

BSE targets the central nervous system of cattle via prion propagation.

Cellular Targets

  • Neurons: Primary site of PrPC expression and PrPSc accumulation → dysfunction, death.
  • Astrocytes: Reactive gliosis (GFAP↑); may propagate prions.
  • Microglia: Activated; inflammatory cytokines but limited clearance.
  • Follicular dendritic cells (lymphoid): Early replication sites (Peyer's patches, tonsils).

Neuroinvasion Route

  1. Gut-associated lymphoid tissue (GALT) → enteric nervous system.
  2. Sympathetic (splanchnic) and vagal nerves → brainstem (dorsal motor nucleus of vagus).
  3. Rostral spread through CNS tracts.

Clinical Manifestations

  • Behavioral: apprehension, aggression, hypersensitivity.
  • Motor: ataxia, tremors, falling, difficulty rising.
  • Autonomic: ruminal stasis, weight loss.
  • Terminal: recumbency, coma, death.

Zoonotic Transmission

  • Consumption of SRM-contaminated products → vCJD in humans.
  • Blood transfusion (4 cases).
  • No evidence of transmission via milk, muscle meat (if SRM-free), or casual contact.

Control Impact

SRM removal + feed ban → near elimination of food-chain exposure. Surveillance ensures early detection.

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