In F. gigantica, the 3 isotypes of CatBs, namely FgCatB1, FgCatB2 and FgCatB3 were cloned from stage specific cDNA libraries (Meemon et al., 2004), and the results suggested that both FgCatB2 and FgCatB3 were expressed in metacercariae and NEJ parasites, whereas FgCatB1 was expressed in all stages but predominantly in the adult (Meemon et al., 2004).