COST (European Co-Operation in the field of Scientific and Technical esearch) Action 855 “Animal Chlamydioses and the Zoonotic Implications” was set up in order to promote and enable cooperation between scientists in veterinary research to address issues relating to chlamydial infections in animals and also their zoonotic potential. To achieve this goal, working groups were tasked to focus on five specific objectives: (1) the development and validation of new and existing diagnostic tests; (2) the field evaluation of diagnostic tests; (3) the assessment of the zoonotic risks associated with animal chlamydioses; (4) to conduct basic research to improve our understanding of chlamydial pathogenesis, virulence factors and associated immune responses; and (5) to develop new vaccines for controlling chlamydial
infection. Through the research activities of the member groups of this European network substantial advances have been made in these areas and presented at the annual conferences in Dublin (2003), Budapest (2004), Siena (2005), Edinburgh (2006), Pulawy (2007) and now culminates with this final meeting in Aarhus. Here we review some of the scientific highlights that have been achieved over the course of the 5 years of the Action.