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December 01, 2021

Human activity likely caused deadly infections in marine mammals

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Fungal infections that have killed porpoises and dolphins in the Pacific Northwest may be linked to nearby human activities such as construction and deforestation.

A research team, led by a scientist at the University of California-Davis, examined stranding reports and necropsy reports from 42 marine mammals that died of confirmed or likely infections with Cryptococcus gattii from 1997-2016 in or near the Salish Sea, which runs between British Columbia and Washington state. In a scientific article published Oct. 22 in Diseases of Aquatic Organisms, the authors also noted the timing of those deaths in comparison with hundreds of confirmed infections in humans, pets, and wild terrestrial animals from 1999 to 2013 as well as land-based air samples that were identified as positive for the pathogen beginning in the early 2000s.

A Dall’s porpoise
A Dall’s porpoise

The marine mammal deaths examined in the study occurred among 26 harbor porpoises, 14 Dall’s porpoises, and two Pacific white-sided dolphins. A related announcement from UC-Davis indicates those deaths occurred near “terrestrial hot spots” for C gattii, which suggests they inhaled spores that originated on nearby land and settled on the water surface.

C gattii infections can cause diseases in mammals’ respiratory and central nervous systems. In humans, the symptoms can include coughing, shortness of breath, chest pain, fever, headache, confusion, changes in behavior, neck pain, nausea, vomiting, and sensitivity to light, according to the Centers for Disease Control and Prevention.

The fungal pathogen lives in decaying material in soil or trees, spreads through airborne basidiospores or yeasts, and historically had been associated with tropical and subtropical regions, the article states. The pathogenic fungus likely spread to the soil and trees of the Pacific Northwest during the early 1990s, though the source is unknown, the UC-Davis announcement states.

The article’s lead author, Sarah J. Teman, who is a research assistant at the SeaDoc Society program within the UC-Davis Karen C. Drayer Wildlife Health Center, said in the announcement that, “As we change the environment in unprecedented ways, we could see more diseases that affect people and wildlife.”