Helicobacter are helicoidal, flagellated, Gram-neg-ative and microaerophilic bacteria that include a large number of species isolated from the gastrointestinal tracts of humans and other animal species, such as Old and New World primates (Dubois et al. 1994, Lundström et al. 2001, Tamashiro et al. 2005). Baskerville and Newell (1988) have described the clinical association of chronic gastritis due to the natu-ral infection of Old World primates (Macaca mulatta) by the bacterial species Helicobacter pylori. Other studies have described how rhesus monkeys also develop gas-tric pathologies, such as peptic ulcers and even stomach cancer, when infected by H. pylori (Dubois et al. 1991, 1994, 1999). Therefore, these animals have been used as models for comparative studies with humans. The in-duced infection of the New World Saimiri sp. resulted in a slight and temporary inflammation of the mucosa in a great majority of animals (Stadtländer et al. 1998). Thus, the results from studies focused on understanding Helicobacter spp infections and associated diseases in various hosts might help to increase our understanding of pathogenic mechanisms (Atherton 2005). A new species of Helicobacter was isolated and as-sociated with chronic colitis in the New World monkey species Saguinus oedipus (Saunders et al. 1999). In 2005, Mello et al. (2005) described the presence of these bacte-ria in the gastric environment of marmosets (Callithrix jacchus) and suggested that a natural bacterial colonisa-tion could occur among these primates. More recently, a new species of Helicobacter (Helicobacter callitrichis) was isolated from C. jacchus (Tamashiro et al. 2005). Additionally, polymorphism in the ABO blood groups of humans and other primates, determined by the expres-sion of the A, B or H(O) antigens, is made up of fucosy-lated and terminal oligosaccharides linked to proteins and lipids, whose main function responsible for and capable of promoting their conservation throughout evolution still remains unknown (Fox et al. 2008). These antigens are distributed in tissues and are primarily localised in epithe-lial cells that function as a barrier to the external environ-ment; hence, it is believed that these antigens could either serve as ligands to specific pathogens or inhibit pathogen-ic interactions at the cell surface (Henry 2001). The direct interactions of H. pylori with ABH anti-gen structures initially demonstrated that individuals ex-pressing fucosylated antigens (H and Lewis b) were more susceptible to disease because the microorganism utilises these epitopes to adhere to host cells (Borén et al. 1993). The presence of such receptors has been investigated in the gastric mucins of rhesus monkeys (Lindén et al. 2004) and the results are consistent with previous evidence.