WASHINGTON, Apr 26: The discovery this week of the fourth US case of mad cow disease was one of two things for food safety experts: a validation of a decade-long focused surveillance regime or a lucky break that highlights the need to revisit previously scrapped efforts for more comprehensive surveillance. For now, calls for greater monitoring seem likely to go unheard, both because the “atypical” case appeared to be a one-in-a-million genetic mutation that officials said posed no threat to the food supply, and because of tightening budgets.(agencies)