What is wrong about eating fast food burgers? There is nothing wrong with it except that it might be contaminated with horse meat. The beef patty we expected is not a beef patty but a horse beef patty instead.
What is wrong with horse meat in meat patties? There is nothing wrong with the horse meat itself. What untoward is how the horse meat is used or how it is produced. Failure to declare the meat type in any product is an offense. The other thing, there was a recent horse meat scandal in which the slaughtered horse are not really intended for human consumption. Such horses were believed to be treated with bute or phenylbutazone. Companies such as Europins and Thermoscientific releasing their Phenylbutazone detection instruments prove that scandal was eminent.
Use of bute in food animals is restricted. It is toxic to bone marrow, has been associated with aplastic anemia. People exposed to said substance has a chance of getting the disease in a rate of 1 out of 30,000. Uncertain results found it to be genotoxic and carcinogenic. EMA (European Medicines Agency) and EFSA (European Food Safety Authority) have not been able to established safe levels of phenylbutazone for food-producing animals since 1997. Thus establishing a safe limit is not possible.