Isolation and molecular characterization of Toxoplasma gondii from naturally infected seabirds on the southern coast of Santa Catarina state, Brazil.

Abstract

Toxoplasma gondii is an intracellular protozoan with worldwide distribution and is of significant importance for One Health due to its zoonotic potential. Although its presence in terrestrial environments is well documented, little is known about its circulation and genetic diversity in the marine ecosystem. This study investigated the occurrence of T. gondii in seabirds rescued from the southern coast of Brazil, focusing on bioassay and molecular characterization. Tissue samples (the heart, brain, liver, lung, and pectoral muscle) from 76 seabirds were received. Of these, 26 were from Larus dominicanus, one Macronectes giganteus, one Pachyptila vittata, five Phalacrocorax brasilianus, two Procellaria aequinoctialis, two Puffinus puffinus, 35 Spheniscus magellanicus, two Sterna hirundo, and two Sula leucogaster. The samples of each bird were processed in pool for peptic digestion. The product of each digestion was inoculated (1 mL/SC) into three mice per bioassay/bird. DNA was extracted for molecular characterization using the PCR-RFLP technique with markers SAG1, 5'-SAG2, 3'-SAG2, Alt. SAG2, SAG3, BTUB, GRA6, c22-8, c29-2, L358, PK1, and Apico. Brain cysts were detected in 16 bioassays. The ToxoDB #170 genotype was identified as an isolate of kelp gull (Larus dominicanus) while another bioassay from the same species did not match the database, suggesting a previously undescribed genotype. Infection occurred through ingestion of sporulated oocysts present in the environment or in fish, bivalves, and crustaceans, which have demonstrated parasitic bioaccumulation. This work highlights the dispersal and infection capacity of different classes of T. gondii hosts and the role of birds as environmental sentinels for marine contamination.