Moreover, in many human infections, the fluke eggs are often not found in the faeces, even after multiple faecal examinations. Furthermore, eggs of "F. hepatica", "F. gigantica" and "Fasciolopsis buski" are morphologically indistinguishable. Therefore, immunonological methods such ELISA and enzyme-linked immunoelectrotransfer blot, also called Western blot, are the most important methods in diagnosis of "F. hepatica" infection. These immunological tests are based on detection of species-specific antibodies from sera. The antigenic preparations used have been primarily derived from extracts of excretory/secretory products from adult worms, or with partially purified fractions. Recently, purified native and recombinant antigens have been used, e.g. recombinant "F. hepatica" cathepsin L-like protease.