Abstract
Bovine Spongiform Encephalopathy (BSE) is primarily an emerging zoonotic disease of cattle of usually over 30 months of age but it also affects other ruminants. Popularly the disease is named as "Mad Cow Disease". The origin of the BSE is still debatable, but most acceptable idea is that it has originated from adaptation and recycling of the sheep scrapie agent called scrapie associated prion protein (PrPsc). BSE has a prolonged incubation period and results in chronic, progressive and ultimately fatal neurodegeneration of the CNS. There is a very strong evidence that infected feed like meat and bone meal (MBM) is the major factor for the transmission of the disease. Although Bangladesh did not experience a BSE outbreak so far, Bangladesh has not yet been declared BSE free by OIE due to lack of scientific risk evaluation for BSE which is limiting Bangladesh in the export of animal byproducts commodities. The objectives of this study were: (I) Identification of hazard for the occurrence of BSE in Bangladesh (II) Identification of release and exposure pathways of prion protein (III) Estimation of risk for the occurrence of BSE in Bangladesh and (IV) Formulation of BSE risk mitigation measures. The scientific data were reviewed, hazards were scheduled and surveys were conducted - on livestock production system, import of livestock and its commodities and use of livestock commodity to identify the hazards present in Bangladesh context. The analysis was done by the "OIE Risk Analysis Framework 2006 and Scientific Steering Committee (SSC) 2003", which consists of hazard identification, risk assessment (external and internal challenge and consequence assessments), risk management and risk communication. From the historical reviews, two external hazards were identified, which were importation of live cattle from Spain and MBM from Germany, Brazil and the Netherlands. The analysis based on the OIE framework - 2006 and SSC - 2003 reveled that these two hazards had negligible or moderate risk, respectively, for the introduction of infectious prion protein (PrPsc) in the cattle population of Bangladesh. Exposure analysis revealed that the Bangladeshi cattle are vegetarian cattle, which are mostly fed on straw, green grass and with limited handmade concentrates. Milk replacer was also not used in calves in Bangladesh. The use of slaughtered waste in the animal feed industry is absent. The human consumes most of the offal produced from livestock. Un-consumable bones are processed to produce bone chips, fertilizers and bone meal for poultry feeds. Scrapie was never prevalent in Bangladesh. Therefore, risk from the internal challenge was negligible in Bangladesh for the occurrence of BSE. This prevented the propagation of BSE infectivity and eliminated BSE infectivity from the system very fast, if that was present. Finally, it was concluded that introduction of PrPsc into cattle population was very negligible. However, to prevent future introduction of BSE into cattle population of Bangladesh we need a sound control strategy.