Objective:To determine whether the requirements for sialic acid varies and whether several types of silaic acid independent receptors utilized for invasion mechanisms of fresh filed isolates collected around Nanay river basin,Iquitos.Methods:The field isolates were cultured as described previously by Jensen and Trager and MR4 protocol with little modifications.The erythrocytes preparation and subsequent enzyme treatment was done as described previously by Sharma.with little modification.Invasion assay was performed as described previously by Sharma et al with little modification.Results:The Nanay river basin isolates showed five types of invasion mechanisms or types of receptors-ligand interactions.Here we observed that an equal numbers of neuraminidase sensitive and resistant invasion receptor-ligand interaction profiles as the most common receptor-ligand invasion profiles.Neuraminidase resistance trypsin sensitive chymotrypsin sensitive(NM_RT_SCT_S) invasion of receptor-ligand interaction profile was found in seven isolates,Five field isolates and one reference strain showed neuraminidase sensitive, trypsin sensitive and chymotrypsin resistant(NM_RT_SCT_R) invasion of receptor-ligand interactions, six isolates including one reference strains dd2 showed neuraminidase sensitive,trypsin and chymotrypsin resistance(NM_ST_RCT_R) indicating its dependence on sialic acids and independence of trypsin and chymotrypsin sensitive proteins.Four isolates showed neuraminidase sensitive, trypsin sensitive and chymotrypsin sensitive(NM_ST_SCT_S) invasion of receptor-ligand interactions, seven isolates were neuraminidase resistant,trypsin sensitive and chymotrypsin resistance (NM_RT_SCT_R) invasion of receptor-ligand interactions,indicating its dependence on trypsin sensitive proteins.Conclusions:The Nanay river basin isolates showed five types of invasion mechanisms or types of receptors-ligand interactions.A full understanding of theses invasion mechanisms may allow the development of novel prophylactic and therapeutic strategies that block erythrocyte receptor-ligand invasion mechanisms. Objective: To determine whether the requirements for sialic acid varies and either several types of silaic acid independent receptors utilized for invasion mechanisms of fresh filed isolates collected around Nanay river basin, Iquitos. Methods: The field isolates were described as previously described by Jensen and Trager and MR4 protocol with little modifications. The erythrocytes preparation and subsequent enzyme treatment was done as previously described by Sharma. with little modification. Invasion assay was performed as described previously by Sharma et al with little modification. Results: The Nanay river basin isolates showed five types of invasion mechanisms or types of receptors-ligand interactions. Here we observed that an equal numbers of neuraminidase sensitive and resistant invasion receptor-ligand interaction profiles as the most common receptor-ligand invasion profiles. Neuraminidase resistance trypsin sensitive chymotrypsin sensitive (NM_RT_SCT_S) invasion of receptor-ligand intera ction profile was found in seven isolates, Five field isolates and one reference strain showed neuraminidase sensitive, trypsin sensitive and chymotrypsin resistant (NM_RT_SCT_R) invasion of receptor-ligand interactions, six isolates including one reference ddd2 showed neuraminidase sensitive, trypsin and chymotrypsin resistance ( NM_ST_RCT_R) indicating its dependence on sialic acids and independence of trypsin and chymotrypsin sensitive proteins. Four Isolates showed neuraminidase sensitive, trypsin sensitive and chymotrypsin sensitive (NM_ST_SCT_S) invasion of receptor-ligand interactions, seven isolates were neuraminidase resistant, trypsin sensitive and chymotrypsin resistance NM_RT_SCT_R) invasion of receptor-ligand interactions, indicating its dependence on trypsin sensitive proteins. Conclusions: The Nanay river basin isolates showed five types of invasion mechanisms or types of receptors-ligand interactions. A full understanding of theses invasion mechanisms may allow the development of novel prophylactic and therapeutic strategies that block erythrocyte receptor-ligand invasion mechanisms.