CONICET | Buscador de Institutos y Recursos Humanos

South American camelids are a source of livestock wealth in Andean countries. In Argentina,there is little information about camelid pathogens, and most of the literature data available are seroprevalence works against virus. Besides, little is known about the immunological status against bacterial agents affecting these animals. In an effort to explore the serological status of Argentinean camelids, we evaluated the presence of serum antibodies against bacterial pathogens involved in pneumonic diseases (Pasteurella multocida and Mannheimia haemolytica) in llamas from different regions of the country. By ELISA, a high seroprevalence for both pathogens was found in the serumsamples; higher optical density (OD) values were obtained when the sera were incubated with heat killed P. multocida as coating antigen compared to M. haemolytica. In addition, a large number of sera analyzed presented high OD values for both microorganisms independently of their origin region. Serum avidity was also evaluated, by means of an assay based on antibody desorption by urea. No correlation was found between the high ODs obtained for P. multocida and the serum avidity. On the other hand, samples reacting with M. haemolytica had lower OD values but higher avidity index. The antigenic recognition pattern for both microorganisms was determined by western blot. Unlike P. multocida, the antigenic recognition pattern of M. haemolytica did not differ among serum samples obtained from animals living in different areas. In summary, we found that camelids can synthetize antibodies that recognize M. haemolytica with high avidity for different antigens of the bacterium, suggesting that Argentinean camelids are in contact with M. haemolytica which is probably a causative agent of subclinical infections. Conversely, specific antibodies for P. multocida were also found, but these sera presented low avidity that is probably the result of a colonization process by this bacterium, or else, to be a consequence of cross-reactivity phenomena.