TPI1 and infection: Nucleotide sequence analyses of the small subunit ribosomal RNA (ssu rRNA), glutamate dehydrogenase (gdh), beta-giardin (bg), and triose phosphate isomerase (tpi) genes have evidenced that G. duodenalis is indeed a multi-species complex composed of eight (A-H) assemblages that differ widely in host range and specificity, with assemblages A and B responsible for ~95% of human infections (4, 28).