Screening of protozoan and microsporidian parasites in feces of great cormorant (Phalacrocorax carbo)

The global population of great cormorants (Phalacrocorax carbo L.) is on the rise. These birds, characterized by rapid metabolism, can deposit large quantities of feces, and because they breed on the land but forage on water, both terrestrial and aquatic environments can be simultaneously affected by their activities. The contribution of great cormorants in the dispersal of bacterial and viral pathogens has been immensely studied; whereas, the occurrence of eukaryotic parasites such as protozoans and microsporidians in these birds is little known. The present study investigated the presence of dispersive stages of potentially zoonotic protozoans belonging to the genera Blastocystis, Giardia and Cryptosporidium, and Microsporidia spores in feces collected from birds inhabiting the breeding colony established at one lake island in Poland, Europe. The feces were examined by coprological techniques (staining with iron hematoxylin, Ziehl-Neelsen, and modified Weber's chromotrope 2R-based trichrome), and with immunofluorescence antibody MERIFLUOR Cryptosporidium/Giardia assay. As found, the Cryptosporidium oocysts were identified rarely in 8% of samples (2/25; 3-5 × 103/g) and no cysts of Giardia and Blastocystis were detected. Microsporidian spores were detected in 4% of samples (1/25) but at very high frequency (4.3 × 104/g). No dispersive stages of parasites were identified in water samples collected from the littoral area near the colony. Despite the profuse defecation of cormorants, their role in the dispersion of the investigated parasites may not be as high as hypothesized.