Feline spongiform encephalopathy (FSE) is a neurodegenerative disease that affects the brains of felines. This disease is known to affect domestic, captive, and wild species of the family Felidae.^[1] Like BSE, this disease can take several years to develop. It is currently believed that this condition is a result of felines ingesting bovine meat contaminated with BSE.^[2]

Clinical signs of FSE typically develop gradually in housecats, ranging from several weeks to months.^[3] Initial signs of the condition include behavioral changes such as aggression, timidity, hiding, hyperesthesia, loss of motor functions, and polydipsia.^[3] Other commonly observed motor signs include gait abnormalities and ataxia, which typically affect the hind legs first. Affected cats may also display poor judgement of distance, and some cats may develop a rapid, crouching, hypermetric gait. Some affected cats may exhibit an abnormal head tilt, tremors, a vacant stare, excessive salivation, decreased grooming behaviors, polyphagia, and dilated pupils.^[3] Ataxia was observed to last for about 8 weeks in the affected animals.

This disease can only be confirmed via a post-mortem examination, which includes identification of bilaterally symmetrical vacuolation of the neuropil and vacuolation in neurones. Lesions are likely to be found in basal ganglia, cerebral cortex and thalamus of the brain.^{[citation needed]}

This is a terminal condition and there is currently no specific treatment for the disease.^[4]In most instances, infected felines die spontaneously within a few months to years, or are euthanized due to this condition.^[3]

This disease was first reported in domestic cats within the United Kingdom in 1990, only four years after the first reports of BSE.^[1][3][5] This disease is caused by a normal prion protein (PrP^C) misfolding after exposure to a pathogenic prion protein (PrP^Sc).^[6] FSE is thought to be related to bovine spongiform encephalopathy (BSE), as well as other forms of transmissible spongiform encephalopathy (TSE) including, Creutzfeldt–Jakob disease (CJD) in humans Scrapie in sheep, and Chronic wasting disease in deer.^[7] Since 1990, cases have been reported in other countries and other feline species in captivity, although most affected felines originated in the UK.^[8] The average age of felines that have been affected by this disease is 11 years of age, with the age range being roughly 2-10 years.^[3] However, there is not any information regarding research into horizontal transmission under normal conditions between felines.^[3]