Animal Prion Diseases

Abstract

Prion diseases occur in many animal species, most notably in ruminants. While scrapie in sheep has been recognised for three centuries and goat scrapie has been recognised for decades, BSE in cattle is a relatively novel disease which was first diagnosed in the UK in the mid 1980s. BSE was most likely caused through dietary exposure to animal feed contaminated with prions and disease was subsequently transmitted to people. The BSE epidemic is almost at an end, but the recent identification of so called atypical forms of BSE and scrapie pose many questions about the possible spectrum of prion diseases in animals and their transmissibility to other species, including humans.The pathogenesis of animal prion diseases has been studied both in natural infections and in experimental animal models. Detection of infectivity is greatly helped by suitable rodent models, in particular transgenic mice. Clinically infected animals show characteristic neuropathology in the brain and spinal cord which is accompanied by the accumulation of a conformationally altered, protease-resistant host protein. The post-mortem diagnosis is based on the detection of this protein, PrP(Sc), but despite recent impressive developments a routine ante-mortem diagnostic test has proved elusive.There is no treatment for prion diseases in animals, but disease outbreaks are controlled through a mixture of movement restrictions on holdings, culling of affected animals and herds and, for classical scrapie in sheep, selective breeding for genetic resistance. Prions are very stable and can remain in the environment for prolonged periods. This poses serious practical questions with regard to the decontamination of infected premises. The control of BSE specifically through restrictions in animal feeding practises has been successful, but the changing spectrum of these diseases plus the economic pressures to relax feed bans and reduce levels of surveillance will require constant vigilance to safeguard animal and public health.

Detection of Atypical H-Type Bovine Spongiform Encephalopathy and Discrimination of Bovine Prion Strains by Real-Time Quaking-Induced Conversion

“…The H and L types of BSE are classified by their respective high and low apparent molecular masses of the unglycosylated PrP Res band. These atypical BSE strains, which are rare (Ͻ100 cases identified worldwide), tend to affect older animals (23) and appear to represent sporadic forms of bovine prion diseases (24). Despite the apparent rarity of the various types of BSE, the facts that H-and L-BSE appear to arise spontaneously and have distinct transmissibilities (20,(25)(26)(27)(28)(29)(30)(31)(32) make it important to be able to detect and differentiate them to reduce the risk of transmission to cattle or other species, such as humans.…”

Distance to slaughter, markets and feed sources used by small-scale food animal operations in the United States

“…Movement of animals to slaughter facilities can also be a route for disease spread between farms, since trucks and equipment used to transport animals to slaughter may be reused for other purposes. Feed deliveries to agricultural operations can also allow dissemination of disease via feed trucks 12 or contaminated feed [13][14][15][16][17] .…”

Detection and Discrimination of Classical and Atypical L-Type Bovine Spongiform Encephalopathy by Real-Time Quaking-Induced Conversion

“…Currently, both of these atypical bovine prion strains, which mainly affect older animals (8), are thought to be sporadic forms of bovine prion diseases (9) and are still rare (less than 100 cases identified worldwide to date).…”