Giardia is frequently detected in stools of non-human primates (NHP). However, a molecular identification has been rarely applied to Giardia isolates from NHP, and the distribution of the zoonotic assemblages A and B remains unclear. Moreover, little is known about the genetic variability among the isolates, although this may contribute to the elucidation of the different transmission pathways, including the role of NHP as a reservoir for human giardiasis. Therefore, 258 Giardia samples from 31 NHP species housed in nine zoological gardens and one sanctuary in Belgium and The Netherlands were characterised based on an assemblage-specific PCR targeting the triose phosphate isomerase (tpi) gene to identify both assemblage A and B infections. Additionally, a multi-locus sequencing approach based on the glutamate dehydrogenase, the tpi and the b-giardin genes was used to examine both the genetic variability and the ability to allocate these isolates to different NHP groups. Overall, assemblage B was the most prevalent (78.6%), but mixed assemblage A and B infections occurred in 32.7% of the samples. Sequencing of the isolates revealed the presence of new polymorphisms for both assemblages and at the three loci examined. The majority of the assemblage B isolates could not be grouped into recently described sub-assemblages, particularly at the tpi gene. Isolates could only be allocated to a specific group when polymorphisms of the three loci were combined. The results confirm that NHP are a potential reservoir for zoonotic transmission and advocate the use of assemblage-specific primers in molecular epidemiological surveys, as mixed infections are likely to be underestimated. The high level of heterogeneity within assemblages indicates that a revised nomenclature of these sub-assemblages is needed, but points out the potency of a multi-locus sequencing approach to unravel the complex epidemiology of Giardia duodenalis. Entamoeba spp. are also frequently detected in faecal samples of non-human primates. Although the majority of these Entamoeba spp. are considered to be harmless, care should be taken when E. histolytica is involved. Infection by this zoonotic gastrointestinal parasite may cause hemorrhagic dysentery, extra-intestinal pathologies and even death. Yet, little is known about the occurrence of these protozoa in NHP. Furthermore, recent molecular analysis of E. histolytica indicates genetic differences between human and NHP isolates. However, the host specificity of these variants remains unknown. In this study we have conducted a molecular survey to determine the distribution of Entamoeba spp. in captive NHP, including E. histolytica. A total of 520 Entamoeba samples previously found in NHP housed at nine zoological gardens and one sanctuary (Belgium and The Netherlands) were characterised based on a previously described PCR-RLHB protocol targeting the small subunit rRNA gene. In addition, E. histolytica isolates were differentiated using a variant specific PCR. The molecular identification revealed the presence of E. histolytica (NHP variant only), E. dispar, E. moshkovskii, E. hartmanni, E. coli. and E. polecki-like. Furthermore, unknown Entamoeba spp. were identified. These results indicate that E. histolytica is present in captive NHP. They also indicate the host specificity of the NHP variant of E. histolytica. Therefore this study also advocates the use of variant specific PCR’s in endemic regions of E. histolytica in order to elucidate the role of NHP as a reservoir for zoonotic transmission. Finally, this study suggests the presence of NHP-specific Entamoeba spp. PhD Student: B Levecke (UGent) Supervision: Francis Vercammen (RZSA) | J Vercruysse (UGent) | P Dorny ( Institute for Tropical Medicine, Antwerp) Partners: JJ Verweij (Dept Parasitology, Leiden University Medical Centre, NL) | T Geurden, Edwin Claerebout, J Vercruysse (Veterinary Medicine, Gent University) Funding: RZSA | UGent | Timeline: 2001 - 2010 Bruno Levecke succesfully defended his PhD dissertation on at Ghent University on 11 March 2010. Congratulations to Bruno and his supervisors!