Mad Cow Disease study reveals developments
A new study published in the August issue of The American Journal of Pathology shows that the autonomic nervous system (ANS) can show signs of infection of Mad Cow Disease prior to the central nervous system (CNS). It was previously thought the ANS only becomes affected by the disease after the CNS has been infected.
Mad Cow Disease or Bovine spongiform encephalopathy (BSE) is a fatal disease affecting cattle. It triggers portions of the brain to turn sponge-like and is caused by the spread of a misfolded form of protein, known as a prion, rather than by a bacterium or virus.
Little is known about the pathogenesis of BSE in the early incubation period and it can take around 60 months after infection for signs of the disease to be visible.
To understand the pathogenesis of BSE, fifty-six calves between four and six months of age were infected orally with BSE from infected cattle. Eighteen calves were inoculated orally with BSE-negative material from calf brainstem as controls. The study also included samples collected from a calf that had died naturally of BSE.
A distinct accumulation of the pathological prion protein was observed in the gut in almost all samples. BSE prions were found in the sympathetic ANS system, located in the thoracic and lumbar spinal cord, starting at 16 months after infection; and in the parasympathetic ANS, located in the sacral region of the spinal cord and the medulla, from 20 months post infection. There was little or no sign of infection in the CNS in these samples.
Lead investigator Martin H. Groschup commented: "The clear involvement of the sympathetic nervous system illustrates that it plays an important role in the pathogenesis of BSE in cattle. Nevertheless, our results also support earlier research that postulated an early parasympathetic route for BSE."
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