DAO prepress abstract  -  doi: 10.3354/dao01931

ABSTRACT: Giardia intestinalis is a microbial eukaryotic parasite that causes diarrheal disease in humans and other vertebrates worldwide. The negative impact on quality of life and economics of G. intestinalis may be increased by its potential status as a zoonosis, or disease transmitted from animals to humans. The zoonotic potential of G. intestinalis has been inferred for over two decades, with human-infecting genotypes (belonging to the two major subgroups, Assemblages A and B) occurring in wildlife and domesticated animals. There are recent reports of G. intestinalis in shellfish, seals, sea lions, and whales, suggesting that marine animals are also potential reservoirs of human disease. However, the prevalence, genetic diversity, and impact of G. intestinalis in marine environments and the role that marine animals play in transmission of this parasite to humans is relatively unexplored. Here, we provide the first thorough molecular characterization of G. intestinalis in marine vertebrates. Using a multi-locus sequencing approach, we identify human-infecting G. intestinalis haplotypes of both Assemblages A and B in the fecal material of dolphins, porpoises, seals, gulls, eiders, and shark. Our results indicate that G. intestinalis is quite prevalent in marine ecosystems, having a wide range of marine hosts capable of harboring zoonotic forms of this parasite. The presence of G. intestinalis in marine ecosystems raises concerns about how this disease might be transmitted among different host species.