BSE

• Bovine Spongiform encephalopathy is a progressive, fatal, infectious neurologic disease in the CNS of cattle caused by prions.
• There are two main forms of BSE: Classical BSE and Atypical BSE.
• The etiologic agent of BSE is a proteinaceous infectious particle (PRION), which are misfolded conformational isoforms of host-encoded proteins that induce protein misfolding, protein aggregation, and disease upon transmission to other organisms.
• PrP Sc is the prion protein.
• Classical BSE is caused by infectious prions.
• Atypical BSE (L-type, H-type) can be caused by contamination of feed by prions that cause the atypical form of scrapie (Nor98).
• Prions are also the cause of scrapie in goats and sheep, chronic wasting disease of deer, transmissible mink encephalopathy; kuru, Creutzfeldt-Jakob disease (fatal insomnia) in humans.
• In this technique, a mixture of proteins is separated based on molecular weight through gel electrophoresis.
• Supportive care may be provided to maintain the well-being of affected animals, but it does not eliminate the underlying prion infection.
• There is no specific treatment for scrapie once an animal is infected.
• Immunohistochemistry, ELISA, Protein Misfolding Cyclic Amplification (PMCA), Quaking-Induced Conversion (QuIC), and Real-Time Quaking-Induced Conversion (R T-QuIC) are other methods used in the diagnosis of scrapie.
• Immunoblotting (Western Blotting) is often used in research to separate and identify proteins.
• Diagnosis of scrapie includes biopsy of nictitating membrane, palatine tonsil, or recto-anal mucosa-associated lymphoid tissue.
• Prevention of scrapie includes culling of infected animals, genetic selection, biosecurity measures, surveillance and monitoring, avoidance of contaminated feed, strict quarantine practices, and public awareness and education.
• Transmission of BSE occurs through contaminated animal-source proteins (meat & bone meal) in cattle rations.
• Calves born to infected cows are at greater risk of acquiring BSE.
• BSE is not transmitted horizontally by contact or aerosols.
• There is no sex or breed predisposition for BSE.
• Most cases of BSE are diagnosed in cattle 3-6 years old.
• The incubation period after exposure to BSE is approximately 2-8 years, with 22 months diagnosed.
• Dairy cows are more affected than beef cattle because dairy cows are more likely to be fed animal-source protein supplements.
• Atypical BSE affects relatively old and results from spontaneous prion protein misfolding and is not related to the ingestion of prion-contaminated feed.
• The clinical signs of BSE are subtle and progress over weeks to months.
• Clinical signs of BSE may be nonspecific and nervous system signs may not be obvious in every case.
• Most animals with BSE reach a terminal state within 3 months of clinical onset.
• Diagnosis of BSE involves detection of the causative agent PrP Sc in brain (medulla oblongata) samples by ELISA, Western immunoblot technique, ultrasensitive in vitro amplification techniques, and real-time quaking-induced conversion.
• Clinical examinations are not definitive diagnoses for BSE and in clinical suspicion, the animal should be euthanized and the brain is subjected to neuropathologic examination.
• Prevention of human exposure to vCJD includes banning meat and bone meal in ruminant feed, diagnosing clinical suspects through passive surveillance, diagnosing animals subjected to emergency slaughtering or dead on the farm through active surveillance, removing specified risk materials (SRMs) from the human feed chain, prohibiting SRMs in animal feeds, destroying all animals suspected of being exposed to contaminated feed, restricting the importation of live cattle and their products, incineration of affected carcasses, and appropriately identifying cattle for efficient surveillance and case
• The periparturient period presents the highest risk of transmission, with elevated PrPsc concentrations in placental tissue, fluids, colostrum, and milk.
• Scrapie is a degenerative and fatal disease that affects the central nervous system of sheep and goats, belonging to a group of diseases known as transmissible spongiform encephalopathies (TSEs), which also include diseases such as Bovine Spongiform Encephalopathy (BSE) in cattle and Creutzfeldt-Jakob Disease (CJD) in humans.
• The misfolded prion protein (PrPsc) leads to the development of a sponge-like pattern in the tissues of the central nervous system.
• Iatrogenic transmission of scrapie is possible, but documented cases are infrequent.
• The disease results from misfolding of the cellular prion protein (PrPc) into an abnormal state (PrPsc) and subsequent aggregation of the abnormal protein in tissues.
• Environmental contamination arises from the shedding of infectious prion protein (PrPsc) in the placenta, feces, saliva, and urine.
• The persistence of PrPsc in the environment is influenced by local climate conditions.
• Affected animals exhibit neurological signs such as tremors of the head and neck, and incoordination.
• Humans became infected with the vCJD-causing agent by eating infected bovine tissues, and in fatal human cases, BSE prion was identified in brain tissue.
• Scrapie is transmitted through oral exposure in contaminated environments and can also be transmitted via contact with conjunctiva, nasal passages, and abraded skin.
• Functions of normal prion (PrPc) include myelin maintenance, memory formation, circadian rhythm stabilization, calcium homeostasis, and neuroprotection.
• Infected animals do not usually become ill for years; however, the clinical signs are progressive and invariably fatal once they develop.