Tyson Foods` stock has dropped two-point-four percent as the Springdale-based company tried to distance itself from the mad cow disease fervor. The world`s largest supplier of beef, chicken and pork still took economic hits related to the discovery of a cow with the disease in Washington state. Three more countries -- Colombia, Ukraine and Venezuela -- joined the growing list of nations imposing temporary bans on import of U-S beef, cutting into Tyson`s multi-million dollar export income. But it may not matter that Tyson and other meat suppliers have not been connected with the case. With overseas markets refusing U-S beef, domestic meat companies stand to lose millions of dollars in sales.