In addition to the cases of mad cow reported in the United Kingdom (78 percent of all cases) and the United States, cases have also been reported in France, Spain, the Netherlands, Portugal, Ireland, Italy, Japan, Saudi Arabia, and Canada. All cases confirmed by laboratory tests were caused by the same form of the disease: Alzheimer's-like brain disorder. Mad cow disease was first discovered in 1986 when British farmers began finding parts of cows that had eaten grass contaminated with the waste products from bacteria that cause mad cow disease. Scientists later learned that the cows' brains contained abnormal proteins that included elements found in human brain tissue. The cows affected were mostly older animals of both sexes fed milked regularly and kept as pets. No case of transmission to humans has been reported so far. However, because the disease affects the brain and mind, it can be difficult to diagnose. Patients may appear normal but will likely develop dementia or some other cognitive impairment over time. Currently, there is no cure for mad cow disease. However, doctors are working on treatments that might help patients during their illness.