Belgian Interbrew's Czech unit Prazske Pivovary has narrowed its net losses to CZK179.4m (US$4.9m) in 2001 from CZK789.3m a year before.   Prazske Pivovary, the second-largest Czech brewer, said the loss pushed its equity further into the red, to CZK1.3 billion from CZK1.1 billion at the end of 2000.