Comparative study on pathogen carriage of white stork (Ciconia ciconia) fledglings in the field and after admission to rehabilitation centers

Abstract

Recent studies by our group have shown that the habitat used by adult storks to forage and the habitat of the colony have an influence on body condition and at least bacterial pathogen carriage in white stork nestlings. Ring recoveries and satellite transmitter data of juvenile Spanish white storks have shown that regardless of the colony of origin, most juvenile white storks will use landfill sites as food source. Thus we hypothesize that this exposure changes the physical condition and pathogen carriage in these juvenile white storks and that samples taken from injured juvenile storks upon admission to rehabilitation centers will reflect the exposure to these food items. We tested prevalence of avian influenza virus (AIV), West Nile virus (WNV) and Newcastle disease virus (NDV), Salmonella and Escherichia coli carrying antimicrobial resistance mechanisms, and for antibodies against AIV, WNV and NDV in 90 (9 adults and 81 nestlings) free-living individuals from four different colonies with a gradient of exposure to human residues from none to 100%, and in 30 juvenile storks admitted to two different rehabilitation centres in the study area. By PCR we did not detect WNV, AIV or ND in any of the storks. Antibodies against AIV were only detected in one individual admitted to a rehabilitation centre, while antibodies against WNV were only present in adult white storks that undertook a full wintering migration as shown by satellite transmitter data in the following winter. Prevalence of Salmonella and NDV antibodies and phenotypic pattern of antimicrobial resistance of commensal E .coli in rehabilitation centre admitted individuals was significantly more similar to the prevalence in free-living individuals exposed to human residues. Thus information from juvenile white storks admitted to rehabilitation centres reflects the condition of juvenile white storks that use landfill sites as food source.